On Fri, 19 Apr 2019 04:35:04 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

device version attribute in mdev sysfs is used by user space software (e.g. libvirt) to query device compatibility for live migration of VFIO mdev devices. This attribute is mandatory if a mdev device supports live migration.

The Subject: doesn't quite match what's being proposed here.

It consists of two parts: common part and vendor proprietary part. common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16).

What purpose does this serve? If it's intended as some sort of namespace feature, shouldn't we first assume that we can only support migration to devices of the same type? Therefore each type would already have its own namespace. Also that would make the trailing bit of the version string listed below in the example redundant. A vendor is still welcome to include this in their version string if they wish, but I think the string should be entirely vendor defined.

vendor proprietary part: this part is varied in length. vendor driver can specify any string to identify a device.

When reading this attribute, it should show device version string of the device of type <type-id>. If a device does not support live migration, it should return errno. When writing a string to this attribute, it returns errno for incompatibility or returns written string length in compatibility case. If a device does not support live migration, it always returns errno.

For user space software to use: 1. Before starting live migration, user space software first reads source side mdev device's version. e.g. "#cat \ /sys/bus/pci/devices/0000\:00\:02.0/5ac1fb20-2bbf-4842-bb7e-36c58c3be9cd/mdev_type/version" 00028086-193b-i915-GVTg_V5_4

2. Then, user space software writes the source side returned version string to device version attribute in target side, and checks the return value. If a negative errno is returned in the target side, then mdev devices in source and target sides are not compatible; If a positive number is returned and it equals to the length of written string, then the two mdev devices in source and target side are compatible. e.g. (a) compatibility case "# echo 00028086-193b-i915-GVTg_V5_4 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version"

(b) incompatibility case "#echo 00028086-193b-i915-GVTg_V5_1 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version" -bash: echo: write error: Invalid argument

3. if two mdev devices are compatible, user space software can start live migration, and vice versa.

Note: if a mdev device does not support live migration, it either does not provide a version attribute, or always returns errno when its version attribute is read/written.

I think it would be cleaner to do the former, not supply the attribute. This seems to do the latter in the sample drivers. Thanks, Alex

Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Erik Skultety <eskultet@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Cornelia Huck <cohuck@redhat.com> Cc: "Tian, Kevin" <kevin.tian@intel.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: "Wang, Zhi A" <zhi.a.wang@intel.com> Cc: Neo Jia <cjia@nvidia.com> Cc: Kirti Wankhede <kwankhede@nvidia.com>

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com> --- Documentation/vfio-mediated-device.txt | 36 ++++++++++++++++++++++++++ samples/vfio-mdev/mbochs.c | 17 ++++++++++++ samples/vfio-mdev/mdpy.c | 16 ++++++++++++ samples/vfio-mdev/mtty.c | 16 ++++++++++++ 4 files changed, 85 insertions(+)

diff --git a/Documentation/vfio-mediated-device.txt b/Documentation/vfio-mediated-device.txt index c3f69bcaf96e..bc28471c0667 100644 --- a/Documentation/vfio-mediated-device.txt +++ b/Documentation/vfio-mediated-device.txt @@ -202,6 +202,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | | |--- create @@ -209,6 +210,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | |--- create @@ -216,6 +218,7 @@ Directories and files under the sysfs for Each Physical Device | |--- available_instances | |--- device_api | |--- description + | |--- version | |--- [devices]

* [mdev_supported_types] @@ -225,6 +228,8 @@ Directories and files under the sysfs for Each Physical Device [<type-id>], device_api, and available_instances are mandatory attributes that should be provided by vendor driver.

+ version is a mandatory attribute if a mdev device supports live migration. + * [<type-id>]

The [<type-id>] name is created by adding the device driver string as a prefix @@ -246,6 +251,35 @@ Directories and files under the sysfs for Each Physical Device This attribute should show the number of devices of type <type-id> that can be created.

+* version + + This attribute is rw. It is used to check whether two devices are compatible + for live migration. If this attribute is missing, then the corresponding mdev + device is regarded as not supporting live migration. + + It consists of two parts: common part and vendor proprietary part. + common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies + device type. e.g., for pci device, it is + "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). + vendor proprietary part: this part is varied in length. vendor driver can + specify any string to identify a device. + + When reading this attribute, it should show device version string of the device + of type <type-id>. If a device does not support live migration, it should + return errno. + When writing a string to this attribute, it returns errno for incompatibility + or returns written string length in compatibility case. If a device does not + support live migration, it always returns errno. + + for example. + # cat \ + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_2/version + 00028086-193b-i915-GVTg_V5_2 + + #echo 00028086-193b-i915-GVTg_V5_2 > \ + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_4/version + -bash: echo: write error: Invalid argument + * [device]

This directory contains links to the devices of type <type-id> that have been @@ -327,12 +361,14 @@ card. | | |-- available_instances | | |-- create | | |-- device_api + | | |-- version | | |-- devices | | `-- name | `-- mtty-2 | |-- available_instances | |-- create | |-- device_api + | |-- version | |-- devices | `-- name |-- mtty_dev diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c index b038aa9f5a70..2f5ba96b91a2 100644 --- a/samples/vfio-mdev/mbochs.c +++ b/samples/vfio-mdev/mbochs.c @@ -1391,11 +1391,28 @@ static ssize_t device_api_show(struct kobject *kobj, struct device *dev, } MDEV_TYPE_ATTR_RO(device_api);

+static ssize_t version_show(struct kobject *kobj, struct device *dev, + char *buf) +{ + /* do not support live migration */ + return -EINVAL; +} + +static ssize_t version_store(struct kobject *kobj, struct device *dev, + const char *buf, size_t count) +{ + /* do not support live migration */ + return -EINVAL; +} + +static MDEV_TYPE_ATTR_RW(version); + static struct attribute *mdev_types_attrs[] = { &mdev_type_attr_name.attr, &mdev_type_attr_description.attr, &mdev_type_attr_device_api.attr, &mdev_type_attr_available_instances.attr, + &mdev_type_attr_version.attr, NULL, };

diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c index cc86bf6566e4..ff15fdfc7d46 100644 --- a/samples/vfio-mdev/mdpy.c +++ b/samples/vfio-mdev/mdpy.c @@ -695,11 +695,27 @@ static ssize_t device_api_show(struct kobject *kobj, struct device *dev, } MDEV_TYPE_ATTR_RO(device_api);

+static ssize_t version_show(struct kobject *kobj, struct device *dev, + char *buf) +{ + /* do not support live migration */ + return -EINVAL; +} + +static ssize_t version_store(struct kobject *kobj, struct device *dev, + const char *buf, size_t count) +{ + /* do not support live migration */ + return -EINVAL; +} +static MDEV_TYPE_ATTR_RW(version); + static struct attribute *mdev_types_attrs[] = { &mdev_type_attr_name.attr, &mdev_type_attr_description.attr, &mdev_type_attr_device_api.attr, &mdev_type_attr_available_instances.attr, + &mdev_type_attr_version.attr, NULL, };

diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c index 1c77c370c92f..4ae3aad3474d 100644 --- a/samples/vfio-mdev/mtty.c +++ b/samples/vfio-mdev/mtty.c @@ -1390,10 +1390,26 @@ static ssize_t device_api_show(struct kobject *kobj, struct device *dev,

MDEV_TYPE_ATTR_RO(device_api);

+static ssize_t version_show(struct kobject *kobj, struct device *dev, + char *buf) +{ + /* do not support live migration */ + return -EINVAL; +} + +static ssize_t version_store(struct kobject *kobj, struct device *dev, + const char *buf, size_t count) +{ + /* do not support live migration */ + return -EINVAL; +} + +static MDEV_TYPE_ATTR_RW(version); static struct attribute *mdev_types_attrs[] = { &mdev_type_attr_name.attr, &mdev_type_attr_device_api.attr, &mdev_type_attr_available_instances.attr, + &mdev_type_attr_version.attr, NULL, };

On Mon, 22 Apr 2019 21:01:52 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

On Mon, Apr 22, 2019 at 10:39:50PM +0800, Alex Williamson wrote:

...

On Fri, 19 Apr 2019 04:35:04 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

device version attribute in mdev sysfs is used by user space software (e.g. libvirt) to query device compatibility for live migration of VFIO mdev devices. This attribute is mandatory if a mdev device supports live migration.

The Subject: doesn't quite match what's being proposed here.

...

It consists of two parts: common part and vendor proprietary part. common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16).

What purpose does this serve? If it's intended as some sort of namespace feature, shouldn't we first assume that we can only support migration to devices of the same type? Therefore each type would already have its own namespace. Also that would make the trailing bit of the version string listed below in the example redundant. A vendor is still welcome to include this in their version string if they wish, but I think the string should be entirely vendor defined.

hi Alex, This common part is a kind of namespace. Because if version string is entirely defined by vendors, I'm worried about if there is a case that one vendor's version string happens to deceive and interfere with another vendor's version checking? e.g. vendor A has a version string like: vendor id + device id + mdev type vendor B has a version string like: device id + vendor id + mdev type but vendor A's vendor id is 0x8086, device id is 0x1217 vendor B's vendor id is 0x1217, device id is 0x8086.

In this corner case, the two vendors may regard the two device is migratable but actually they are not.

That's the reason for this common part that serve as a kind of namespace that all vendors will comply with to avoid overlap.

If we assume that migration can only occur between matching mdev types, this is redundant, each type already has their own namespace.

...

...

vendor proprietary part: this part is varied in length. vendor driver can specify any string to identify a device.

When reading this attribute, it should show device version string of the device of type <type-id>. If a device does not support live migration, it should return errno. When writing a string to this attribute, it returns errno for incompatibility or returns written string length in compatibility case. If a device does not support live migration, it always returns errno.

For user space software to use: 1. Before starting live migration, user space software first reads source side mdev device's version. e.g. "#cat \ /sys/bus/pci/devices/0000\:00\:02.0/5ac1fb20-2bbf-4842-bb7e-36c58c3be9cd/mdev_type/version" 00028086-193b-i915-GVTg_V5_4

2. Then, user space software writes the source side returned version string to device version attribute in target side, and checks the return value. If a negative errno is returned in the target side, then mdev devices in source and target sides are not compatible; If a positive number is returned and it equals to the length of written string, then the two mdev devices in source and target side are compatible. e.g. (a) compatibility case "# echo 00028086-193b-i915-GVTg_V5_4 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version"

(b) incompatibility case "#echo 00028086-193b-i915-GVTg_V5_1 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version" -bash: echo: write error: Invalid argument

3. if two mdev devices are compatible, user space software can start live migration, and vice versa.

Note: if a mdev device does not support live migration, it either does not provide a version attribute, or always returns errno when its version attribute is read/written.

I think it would be cleaner to do the former, not supply the attribute. This seems to do the latter in the sample drivers. Thanks, Ok. you are right! what about just keep one sample driver to show how to do the latter, and let the others do the former?

I'd rather that if a vendor driver doesn't support features requiring the version attribute that they don't implement it. It's confusing to developers looking at the sample driver for guidance if we have different implementations. Of course if you'd like to add migration support to one of the sample drivers, that'd be very welcome. Thanks, Alex

...

...

Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Erik Skultety <eskultet@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Cornelia Huck <cohuck@redhat.com> Cc: "Tian, Kevin" <kevin.tian@intel.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: "Wang, Zhi A" <zhi.a.wang@intel.com> Cc: Neo Jia <cjia@nvidia.com> Cc: Kirti Wankhede <kwankhede@nvidia.com>

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com> --- Documentation/vfio-mediated-device.txt | 36 ++++++++++++++++++++++++++ samples/vfio-mdev/mbochs.c | 17 ++++++++++++ samples/vfio-mdev/mdpy.c | 16 ++++++++++++ samples/vfio-mdev/mtty.c | 16 ++++++++++++ 4 files changed, 85 insertions(+)

diff --git a/Documentation/vfio-mediated-device.txt b/Documentation/vfio-mediated-device.txt index c3f69bcaf96e..bc28471c0667 100644 --- a/Documentation/vfio-mediated-device.txt +++ b/Documentation/vfio-mediated-device.txt @@ -202,6 +202,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | | |--- create @@ -209,6 +210,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | |--- create @@ -216,6 +218,7 @@ Directories and files under the sysfs for Each Physical Device | |--- available_instances | |--- device_api | |--- description + | |--- version | |--- [devices]

* [mdev_supported_types] @@ -225,6 +228,8 @@ Directories and files under the sysfs for Each Physical Device [<type-id>], device_api, and available_instances are mandatory attributes that should be provided by vendor driver.

+ version is a mandatory attribute if a mdev device supports live migration. + * [<type-id>]

The [<type-id>] name is created by adding the device driver string as a prefix @@ -246,6 +251,35 @@ Directories and files under the sysfs for Each Physical Device This attribute should show the number of devices of type <type-id> that can be created.

+* version + + This attribute is rw. It is used to check whether two devices are compatible + for live migration. If this attribute is missing, then the corresponding mdev + device is regarded as not supporting live migration. + + It consists of two parts: common part and vendor proprietary part. + common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies + device type. e.g., for pci device, it is + "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). + vendor proprietary part: this part is varied in length. vendor driver can + specify any string to identify a device. + + When reading this attribute, it should show device version string of the device + of type <type-id>. If a device does not support live migration, it should + return errno. + When writing a string to this attribute, it returns errno for incompatibility + or returns written string length in compatibility case. If a device does not + support live migration, it always returns errno. + + for example. + # cat \ + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_2/version + 00028086-193b-i915-GVTg_V5_2 + + #echo 00028086-193b-i915-GVTg_V5_2 > \ + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_4/version + -bash: echo: write error: Invalid argument + * [device]

This directory contains links to the devices of type <type-id> that have been @@ -327,12 +361,14 @@ card. | | |-- available_instances | | |-- create | | |-- device_api + | | |-- version | | |-- devices | | `-- name | `-- mtty-2 | |-- available_instances | |-- create | |-- device_api + | |-- version | |-- devices | `-- name |-- mtty_dev diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c index b038aa9f5a70..2f5ba96b91a2 100644 --- a/samples/vfio-mdev/mbochs.c +++ b/samples/vfio-mdev/mbochs.c @@ -1391,11 +1391,28 @@ static ssize_t device_api_show(struct kobject *kobj, struct device *dev, } MDEV_TYPE_ATTR_RO(device_api);

+static ssize_t version_show(struct kobject *kobj, struct device *dev, + char *buf) +{ + /* do not support live migration */ + return -EINVAL; +} + +static ssize_t version_store(struct kobject *kobj, struct device *dev, + const char *buf, size_t count) +{ + /* do not support live migration */ + return -EINVAL; +} + +static MDEV_TYPE_ATTR_RW(version); + static struct attribute *mdev_types_attrs[] = { &mdev_type_attr_name.attr, &mdev_type_attr_description.attr, &mdev_type_attr_device_api.attr, &mdev_type_attr_available_instances.attr, + &mdev_type_attr_version.attr, NULL, };

diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c index cc86bf6566e4..ff15fdfc7d46 100644 --- a/samples/vfio-mdev/mdpy.c +++ b/samples/vfio-mdev/mdpy.c @@ -695,11 +695,27 @@ static ssize_t device_api_show(struct kobject *kobj, struct device *dev, } MDEV_TYPE_ATTR_RO(device_api);

+static ssize_t version_show(struct kobject *kobj, struct device *dev, + char *buf) +{ + /* do not support live migration */ + return -EINVAL; +} + +static ssize_t version_store(struct kobject *kobj, struct device *dev, + const char *buf, size_t count) +{ + /* do not support live migration */ + return -EINVAL; +} +static MDEV_TYPE_ATTR_RW(version); + static struct attribute *mdev_types_attrs[] = { &mdev_type_attr_name.attr, &mdev_type_attr_description.attr, &mdev_type_attr_device_api.attr, &mdev_type_attr_available_instances.attr, + &mdev_type_attr_version.attr, NULL, };

diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c index 1c77c370c92f..4ae3aad3474d 100644 --- a/samples/vfio-mdev/mtty.c +++ b/samples/vfio-mdev/mtty.c @@ -1390,10 +1390,26 @@ static ssize_t device_api_show(struct kobject *kobj, struct device *dev,

MDEV_TYPE_ATTR_RO(device_api);

+static ssize_t version_show(struct kobject *kobj, struct device *dev, + char *buf) +{ + /* do not support live migration */ + return -EINVAL; +} + +static ssize_t version_store(struct kobject *kobj, struct device *dev, + const char *buf, size_t count) +{ + /* do not support live migration */ + return -EINVAL; +} + +static MDEV_TYPE_ATTR_RW(version); static struct attribute *mdev_types_attrs[] = { &mdev_type_attr_name.attr, &mdev_type_attr_device_api.attr, &mdev_type_attr_available_instances.attr, + &mdev_type_attr_version.attr, NULL, };

_______________________________________________ intel-gvt-dev mailing list intel-gvt-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev

On Tue, Apr 23, 2019 at 11:02:56PM +0800, Alex Williamson wrote:

On Tue, 23 Apr 2019 01:41:57 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

On Tue, Apr 23, 2019 at 09:21:00AM +0800, Alex Williamson wrote:

...

On Mon, 22 Apr 2019 21:01:52 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

On Mon, Apr 22, 2019 at 10:39:50PM +0800, Alex Williamson wrote:

...

On Fri, 19 Apr 2019 04:35:04 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

device version attribute in mdev sysfs is used by user space software (e.g. libvirt) to query device compatibility for live migration of VFIO mdev devices. This attribute is mandatory if a mdev device supports live migration.

The Subject: doesn't quite match what's being proposed here.

...

It consists of two parts: common part and vendor proprietary part. common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16).

What purpose does this serve? If it's intended as some sort of namespace feature, shouldn't we first assume that we can only support migration to devices of the same type? Therefore each type would already have its own namespace. Also that would make the trailing bit of the version string listed below in the example redundant. A vendor is still welcome to include this in their version string if they wish, but I think the string should be entirely vendor defined.

hi Alex, This common part is a kind of namespace. Because if version string is entirely defined by vendors, I'm worried about if there is a case that one vendor's version string happens to deceive and interfere with another vendor's version checking? e.g. vendor A has a version string like: vendor id + device id + mdev type vendor B has a version string like: device id + vendor id + mdev type but vendor A's vendor id is 0x8086, device id is 0x1217 vendor B's vendor id is 0x1217, device id is 0x8086.

In this corner case, the two vendors may regard the two device is migratable but actually they are not.

That's the reason for this common part that serve as a kind of namespace that all vendors will comply with to avoid overlap.

If we assume that migration can only occur between matching mdev types, this is redundant, each type already has their own namespace.

hi Alex, do you mean user space software like libvirt needs to first check whether mdev type is matching and then check whether version is matching?

Yes.

may I know the drawback of defining the this common part? common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). By doing so, user space software has no need to first check whether mdev type is matching. A confident vendor driver can even allow devices migrating between different mdev types.

...

if user space software only checks version for migration, it means vendor driver has to include mdev type in their vendor proprietary part string, right?

Userspace attempting to migrate an nvidia-64 to an i915-GVT_V5_4 would be a failure on the part of the user.

...

Another thing is that could there be any future mdev parent driver that applies to all mdev devices, just like vfio-pci? like Yi's vfio-pci-mdev driver (https://lkml.org/lkml/2019/3/13/114)?

For starters, this is just a sample driver from which vendor specific mdev drivers could be forked to support these features, but additionally, the type is defined by the vendor driver, so even a meta driver like vfio-pci-mdev could create types like "vfio-pci-mdev-8086_10c9_abcdef" if it wanted to provide that specific device. The "vfio-pci-mdev-type1" is just a sample implementation to say "the native type of the thing bound to me" and it's going to have limited usefulness for any sort of persistence to userspace. Thus, it's a sample driver. Thanks, Thanks for this explanation:)

...

...

...

...

...

vendor proprietary part: this part is varied in length. vendor driver can specify any string to identify a device.

When reading this attribute, it should show device version string of the device of type <type-id>. If a device does not support live migration, it should return errno. When writing a string to this attribute, it returns errno for incompatibility or returns written string length in compatibility case. If a device does not support live migration, it always returns errno.

For user space software to use: 1. Before starting live migration, user space software first reads source side mdev device's version. e.g. "#cat \ /sys/bus/pci/devices/0000\:00\:02.0/5ac1fb20-2bbf-4842-bb7e-36c58c3be9cd/mdev_type/version" 00028086-193b-i915-GVTg_V5_4

2. Then, user space software writes the source side returned version string to device version attribute in target side, and checks the return value. If a negative errno is returned in the target side, then mdev devices in source and target sides are not compatible; If a positive number is returned and it equals to the length of written string, then the two mdev devices in source and target side are compatible. e.g. (a) compatibility case "# echo 00028086-193b-i915-GVTg_V5_4 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version"

(b) incompatibility case "#echo 00028086-193b-i915-GVTg_V5_1 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version" -bash: echo: write error: Invalid argument

3. if two mdev devices are compatible, user space software can start live migration, and vice versa.

Note: if a mdev device does not support live migration, it either does not provide a version attribute, or always returns errno when its version attribute is read/written.

I think it would be cleaner to do the former, not supply the attribute. This seems to do the latter in the sample drivers. Thanks, Ok. you are right! what about just keep one sample driver to show how to do the latter, and let the others do the former?

I'd rather that if a vendor driver doesn't support features requiring the version attribute that they don't implement it. It's confusing to developers looking at the sample driver for guidance if we have different implementations. Of course if you'd like to add migration support to one of the sample drivers, that'd be very welcome. Thanks,

Got it:)

Thanks! Yan

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...

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Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Erik Skultety <eskultet@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Cornelia Huck <cohuck@redhat.com> Cc: "Tian, Kevin" <kevin.tian@intel.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: "Wang, Zhi A" <zhi.a.wang@intel.com> Cc: Neo Jia <cjia@nvidia.com> Cc: Kirti Wankhede <kwankhede@nvidia.com>

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com> --- Documentation/vfio-mediated-device.txt | 36 ++++++++++++++++++++++++++ samples/vfio-mdev/mbochs.c | 17 ++++++++++++ samples/vfio-mdev/mdpy.c | 16 ++++++++++++ samples/vfio-mdev/mtty.c | 16 ++++++++++++ 4 files changed, 85 insertions(+)

diff --git a/Documentation/vfio-mediated-device.txt b/Documentation/vfio-mediated-device.txt index c3f69bcaf96e..bc28471c0667 100644 --- a/Documentation/vfio-mediated-device.txt +++ b/Documentation/vfio-mediated-device.txt @@ -202,6 +202,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | | |--- create @@ -209,6 +210,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | |--- create @@ -216,6 +218,7 @@ Directories and files under the sysfs for Each Physical Device | |--- available_instances | |--- device_api | |--- description + | |--- version | |--- [devices]

* [mdev_supported_types] @@ -225,6 +228,8 @@ Directories and files under the sysfs for Each Physical Device [<type-id>], device_api, and available_instances are mandatory attributes that should be provided by vendor driver.

+ version is a mandatory attribute if a mdev device supports live migration. + * [<type-id>]

The [<type-id>] name is created by adding the device driver string as a prefix @@ -246,6 +251,35 @@ Directories and files under the sysfs for Each Physical Device This attribute should show the number of devices of type <type-id> that can be created.

+* version + + This attribute is rw. It is used to check whether two devices are compatible + for live migration. If this attribute is missing, then the corresponding mdev + device is regarded as not supporting live migration. + + It consists of two parts: common part and vendor proprietary part. + common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies + device type. e.g., for pci device, it is + "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). + vendor proprietary part: this part is varied in length. vendor driver can + specify any string to identify a device. + + When reading this attribute, it should show device version string of the device + of type <type-id>. If a device does not support live migration, it should + return errno. + When writing a string to this attribute, it returns errno for incompatibility + or returns written string length in compatibility case. If a device does not + support live migration, it always returns errno. + + for example. + # cat \ + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_2/version + 00028086-193b-i915-GVTg_V5_2 + + #echo 00028086-193b-i915-GVTg_V5_2 > \ + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_4/version + -bash: echo: write error: Invalid argument + * [device]

This directory contains links to the devices of type <type-id> that have been @@ -327,12 +361,14 @@ card. | | |-- available_instances | | |-- create | | |-- device_api + | | |-- version | | |-- devices | | `-- name | `-- mtty-2 | |-- available_instances | |-- create | |-- device_api + | |-- version | |-- devices | `-- name |-- mtty_dev diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c index b038aa9f5a70..2f5ba96b91a2 100644 --- a/samples/vfio-mdev/mbochs.c +++ b/samples/vfio-mdev/mbochs.c @@ -1391,11 +1391,28 @@ static ssize_t device_api_show(struct kobject *kobj, struct device *dev, } MDEV_TYPE_ATTR_RO(device_api);

+static ssize_t version_show(struct kobject *kobj, struct device *dev, + char *buf) +{ + /* do not support live migration */ + return -EINVAL; +} + +static ssize_t version_store(struct kobject *kobj, struct device *dev, + const char *buf, size_t count) +{ + /* do not support live migration */ + return -EINVAL; +} + +static MDEV_TYPE_ATTR_RW(version); + static struct attribute *mdev_types_attrs[] = { &mdev_type_attr_name.attr, &mdev_type_attr_description.attr, &mdev_type_attr_device_api.attr, &mdev_type_attr_available_instances.attr, + &mdev_type_attr_version.attr, NULL, };

diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c index cc86bf6566e4..ff15fdfc7d46 100644 --- a/samples/vfio-mdev/mdpy.c +++ b/samples/vfio-mdev/mdpy.c @@ -695,11 +695,27 @@ static ssize_t device_api_show(struct kobject *kobj, struct device *dev, } MDEV_TYPE_ATTR_RO(device_api);

+static ssize_t version_show(struct kobject *kobj, struct device *dev, + char *buf) +{ + /* do not support live migration */ + return -EINVAL; +} + +static ssize_t version_store(struct kobject *kobj, struct device *dev, + const char *buf, size_t count) +{ + /* do not support live migration */ + return -EINVAL; +} +static MDEV_TYPE_ATTR_RW(version); + static struct attribute *mdev_types_attrs[] = { &mdev_type_attr_name.attr, &mdev_type_attr_description.attr, &mdev_type_attr_device_api.attr, &mdev_type_attr_available_instances.attr, + &mdev_type_attr_version.attr, NULL, };

diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c index 1c77c370c92f..4ae3aad3474d 100644 --- a/samples/vfio-mdev/mtty.c +++ b/samples/vfio-mdev/mtty.c @@ -1390,10 +1390,26 @@ static ssize_t device_api_show(struct kobject *kobj, struct device *dev,

MDEV_TYPE_ATTR_RO(device_api);

+static ssize_t version_show(struct kobject *kobj, struct device *dev, + char *buf) +{ + /* do not support live migration */ + return -EINVAL; +} + +static ssize_t version_store(struct kobject *kobj, struct device *dev, + const char *buf, size_t count) +{ + /* do not support live migration */ + return -EINVAL; +} + +static MDEV_TYPE_ATTR_RW(version); static struct attribute *mdev_types_attrs[] = { &mdev_type_attr_name.attr, &mdev_type_attr_device_api.attr, &mdev_type_attr_available_instances.attr, + &mdev_type_attr_version.attr, NULL, };

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On Wed, Apr 24, 2019 at 10:14:50PM +0800, Alex Williamson wrote:

On Tue, 23 Apr 2019 23:39:34 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

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On Tue, Apr 23, 2019 at 11:02:56PM +0800, Alex Williamson wrote:

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On Tue, 23 Apr 2019 01:41:57 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

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On Tue, Apr 23, 2019 at 09:21:00AM +0800, Alex Williamson wrote:

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On Mon, 22 Apr 2019 21:01:52 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

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On Mon, Apr 22, 2019 at 10:39:50PM +0800, Alex Williamson wrote: > On Fri, 19 Apr 2019 04:35:04 -0400 > Yan Zhao <yan.y.zhao@intel.com> wrote: > > > device version attribute in mdev sysfs is used by user space software > > (e.g. libvirt) to query device compatibility for live migration of VFIO > > mdev devices. This attribute is mandatory if a mdev device supports live > > migration. > > The Subject: doesn't quite match what's being proposed here. > > > It consists of two parts: common part and vendor proprietary part. > > common part: 32 bit. lower 16 bits is vendor id and higher 16 bits > > identifies device type. e.g., for pci device, it is > > "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). > > What purpose does this serve? If it's intended as some sort of > namespace feature, shouldn't we first assume that we can only support > migration to devices of the same type? Therefore each type would > already have its own namespace. Also that would make the trailing bit > of the version string listed below in the example redundant. A vendor > is still welcome to include this in their version string if they wish, > but I think the string should be entirely vendor defined. > hi Alex, This common part is a kind of namespace. Because if version string is entirely defined by vendors, I'm worried about if there is a case that one vendor's version string happens to deceive and interfere with another vendor's version checking? e.g. vendor A has a version string like: vendor id + device id + mdev type vendor B has a version string like: device id + vendor id + mdev type but vendor A's vendor id is 0x8086, device id is 0x1217 vendor B's vendor id is 0x1217, device id is 0x8086.

In this corner case, the two vendors may regard the two device is migratable but actually they are not.

That's the reason for this common part that serve as a kind of namespace that all vendors will comply with to avoid overlap.

If we assume that migration can only occur between matching mdev types, this is redundant, each type already has their own namespace.

hi Alex, do you mean user space software like libvirt needs to first check whether mdev type is matching and then check whether version is matching?

Yes.

may I know the drawback of defining the this common part? common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). By doing so, user space software has no need to first check whether mdev type is matching. A confident vendor driver can even allow devices migrating between different mdev types.

It's not practical to expect userspace to test the version of every mdev type in the system to determine a match, let alone across a data center. Additionally, in order to be migration compatible the mdev types must be software compatible to the VM, which is the basic definition of the differences between mdev types. Therefore let me flip the question around, why would a vendor driver choose to create a new mdev type for software compatible devices? If the vendor wants to maintain compatibility, indicate basic compatibility using the same mdev type. The original intention of the version attribute is to be entirely opaque to userspace, introducing "common" parts is unnecessary as above, degrades the original concept, and only defines a solution for PCI devices. Thanks,

ok. Got it. Thanks for explanation. I'll remove this common part in next revision.

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if user space software only checks version for migration, it means vendor driver has to include mdev type in their vendor proprietary part string, right?

Userspace attempting to migrate an nvidia-64 to an i915-GVT_V5_4 would be a failure on the part of the user.

...

Another thing is that could there be any future mdev parent driver that applies to all mdev devices, just like vfio-pci? like Yi's vfio-pci-mdev driver (https://lkml.org/lkml/2019/3/13/114)?

For starters, this is just a sample driver from which vendor specific mdev drivers could be forked to support these features, but additionally, the type is defined by the vendor driver, so even a meta driver like vfio-pci-mdev could create types like "vfio-pci-mdev-8086_10c9_abcdef" if it wanted to provide that specific device. The "vfio-pci-mdev-type1" is just a sample implementation to say "the native type of the thing bound to me" and it's going to have limited usefulness for any sort of persistence to userspace. Thus, it's a sample driver. Thanks, Thanks for this explanation:)

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> > vendor proprietary part: this part is varied in length. vendor driver can > > specify any string to identify a device. > > > > When reading this attribute, it should show device version string of the > > device of type <type-id>. If a device does not support live migration, it > > should return errno. > > When writing a string to this attribute, it returns errno for > > incompatibility or returns written string length in compatibility case. > > If a device does not support live migration, it always returns errno. > > > > For user space software to use: > > 1. > > Before starting live migration, user space software first reads source side > > mdev device's version. e.g. > > "#cat \ > > /sys/bus/pci/devices/0000\:00\:02.0/5ac1fb20-2bbf-4842-bb7e-36c58c3be9cd/mdev_type/version" > > 00028086-193b-i915-GVTg_V5_4 > > > > 2. > > Then, user space software writes the source side returned version string > > to device version attribute in target side, and checks the return value. > > If a negative errno is returned in the target side, then mdev devices in > > source and target sides are not compatible; > > If a positive number is returned and it equals to the length of written > > string, then the two mdev devices in source and target side are compatible. > > e.g. > > (a) compatibility case > > "# echo 00028086-193b-i915-GVTg_V5_4 > > > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version" > > > > (b) incompatibility case > > "#echo 00028086-193b-i915-GVTg_V5_1 > > > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version" > > -bash: echo: write error: Invalid argument > > > > 3. if two mdev devices are compatible, user space software can start > > live migration, and vice versa. > > > > Note: if a mdev device does not support live migration, it either does > > not provide a version attribute, or always returns errno when its version > > attribute is read/written. > > I think it would be cleaner to do the former, not supply the > attribute. This seems to do the latter in the sample drivers. Thanks, Ok. you are right! what about just keep one sample driver to show how to do the latter, and let the others do the former?

I'd rather that if a vendor driver doesn't support features requiring the version attribute that they don't implement it. It's confusing to developers looking at the sample driver for guidance if we have different implementations. Of course if you'd like to add migration support to one of the sample drivers, that'd be very welcome. Thanks,

Got it:)

Thanks! Yan

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...

> > Cc: Alex Williamson <alex.williamson@redhat.com> > > Cc: Erik Skultety <eskultet@redhat.com> > > Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> > > Cc: Cornelia Huck <cohuck@redhat.com> > > Cc: "Tian, Kevin" <kevin.tian@intel.com> > > Cc: Zhenyu Wang <zhenyuw@linux.intel.com> > > Cc: "Wang, Zhi A" <zhi.a.wang@intel.com> > > Cc: Neo Jia <cjia@nvidia.com> > > Cc: Kirti Wankhede <kwankhede@nvidia.com> > > > > Signed-off-by: Yan Zhao <yan.y.zhao@intel.com> > > --- > > Documentation/vfio-mediated-device.txt | 36 ++++++++++++++++++++++++++ > > samples/vfio-mdev/mbochs.c | 17 ++++++++++++ > > samples/vfio-mdev/mdpy.c | 16 ++++++++++++ > > samples/vfio-mdev/mtty.c | 16 ++++++++++++ > > 4 files changed, 85 insertions(+) > > > > diff --git a/Documentation/vfio-mediated-device.txt b/Documentation/vfio-mediated-device.txt > > index c3f69bcaf96e..bc28471c0667 100644 > > --- a/Documentation/vfio-mediated-device.txt > > +++ b/Documentation/vfio-mediated-device.txt > > @@ -202,6 +202,7 @@ Directories and files under the sysfs for Each Physical Device > > | | |--- available_instances > > | | |--- device_api > > | | |--- description > > + | | |--- version > > | | |--- [devices] > > | |--- [<type-id>] > > | | |--- create > > @@ -209,6 +210,7 @@ Directories and files under the sysfs for Each Physical Device > > | | |--- available_instances > > | | |--- device_api > > | | |--- description > > + | | |--- version > > | | |--- [devices] > > | |--- [<type-id>] > > | |--- create > > @@ -216,6 +218,7 @@ Directories and files under the sysfs for Each Physical Device > > | |--- available_instances > > | |--- device_api > > | |--- description > > + | |--- version > > | |--- [devices] > > > > * [mdev_supported_types] > > @@ -225,6 +228,8 @@ Directories and files under the sysfs for Each Physical Device > > [<type-id>], device_api, and available_instances are mandatory attributes > > that should be provided by vendor driver. > > > > + version is a mandatory attribute if a mdev device supports live migration. > > + > > * [<type-id>] > > > > The [<type-id>] name is created by adding the device driver string as a prefix > > @@ -246,6 +251,35 @@ Directories and files under the sysfs for Each Physical Device > > This attribute should show the number of devices of type <type-id> that can be > > created. > > > > +* version > > + > > + This attribute is rw. It is used to check whether two devices are compatible > > + for live migration. If this attribute is missing, then the corresponding mdev > > + device is regarded as not supporting live migration. > > + > > + It consists of two parts: common part and vendor proprietary part. > > + common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies > > + device type. e.g., for pci device, it is > > + "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). > > + vendor proprietary part: this part is varied in length. vendor driver can > > + specify any string to identify a device. > > + > > + When reading this attribute, it should show device version string of the device > > + of type <type-id>. If a device does not support live migration, it should > > + return errno. > > + When writing a string to this attribute, it returns errno for incompatibility > > + or returns written string length in compatibility case. If a device does not > > + support live migration, it always returns errno. > > + > > + for example. > > + # cat \ > > + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_2/version > > + 00028086-193b-i915-GVTg_V5_2 > > + > > + #echo 00028086-193b-i915-GVTg_V5_2 > \ > > + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_4/version > > + -bash: echo: write error: Invalid argument > > + > > * [device] > > > > This directory contains links to the devices of type <type-id> that have been > > @@ -327,12 +361,14 @@ card. > > | | |-- available_instances > > | | |-- create > > | | |-- device_api > > + | | |-- version > > | | |-- devices > > | | `-- name > > | `-- mtty-2 > > | |-- available_instances > > | |-- create > > | |-- device_api > > + | |-- version > > | |-- devices > > | `-- name > > |-- mtty_dev > > diff --git a/samples/vfio-mdev/mbochs.c b/samples/vfio-mdev/mbochs.c > > index b038aa9f5a70..2f5ba96b91a2 100644 > > --- a/samples/vfio-mdev/mbochs.c > > +++ b/samples/vfio-mdev/mbochs.c > > @@ -1391,11 +1391,28 @@ static ssize_t device_api_show(struct kobject *kobj, struct device *dev, > > } > > MDEV_TYPE_ATTR_RO(device_api); > > > > +static ssize_t version_show(struct kobject *kobj, struct device *dev, > > + char *buf) > > +{ > > + /* do not support live migration */ > > + return -EINVAL; > > +} > > + > > +static ssize_t version_store(struct kobject *kobj, struct device *dev, > > + const char *buf, size_t count) > > +{ > > + /* do not support live migration */ > > + return -EINVAL; > > +} > > + > > +static MDEV_TYPE_ATTR_RW(version); > > + > > static struct attribute *mdev_types_attrs[] = { > > &mdev_type_attr_name.attr, > > &mdev_type_attr_description.attr, > > &mdev_type_attr_device_api.attr, > > &mdev_type_attr_available_instances.attr, > > + &mdev_type_attr_version.attr, > > NULL, > > }; > > > > diff --git a/samples/vfio-mdev/mdpy.c b/samples/vfio-mdev/mdpy.c > > index cc86bf6566e4..ff15fdfc7d46 100644 > > --- a/samples/vfio-mdev/mdpy.c > > +++ b/samples/vfio-mdev/mdpy.c > > @@ -695,11 +695,27 @@ static ssize_t device_api_show(struct kobject *kobj, struct device *dev, > > } > > MDEV_TYPE_ATTR_RO(device_api); > > > > +static ssize_t version_show(struct kobject *kobj, struct device *dev, > > + char *buf) > > +{ > > + /* do not support live migration */ > > + return -EINVAL; > > +} > > + > > +static ssize_t version_store(struct kobject *kobj, struct device *dev, > > + const char *buf, size_t count) > > +{ > > + /* do not support live migration */ > > + return -EINVAL; > > +} > > +static MDEV_TYPE_ATTR_RW(version); > > + > > static struct attribute *mdev_types_attrs[] = { > > &mdev_type_attr_name.attr, > > &mdev_type_attr_description.attr, > > &mdev_type_attr_device_api.attr, > > &mdev_type_attr_available_instances.attr, > > + &mdev_type_attr_version.attr, > > NULL, > > }; > > > > diff --git a/samples/vfio-mdev/mtty.c b/samples/vfio-mdev/mtty.c > > index 1c77c370c92f..4ae3aad3474d 100644 > > --- a/samples/vfio-mdev/mtty.c > > +++ b/samples/vfio-mdev/mtty.c > > @@ -1390,10 +1390,26 @@ static ssize_t device_api_show(struct kobject *kobj, struct device *dev, > > > > MDEV_TYPE_ATTR_RO(device_api); > > > > +static ssize_t version_show(struct kobject *kobj, struct device *dev, > > + char *buf) > > +{ > > + /* do not support live migration */ > > + return -EINVAL; > > +} > > + > > +static ssize_t version_store(struct kobject *kobj, struct device *dev, > > + const char *buf, size_t count) > > +{ > > + /* do not support live migration */ > > + return -EINVAL; > > +} > > + > > +static MDEV_TYPE_ATTR_RW(version); > > static struct attribute *mdev_types_attrs[] = { > > &mdev_type_attr_name.attr, > > &mdev_type_attr_device_api.attr, > > &mdev_type_attr_available_instances.attr, > > + &mdev_type_attr_version.attr, > > NULL, > > }; > > > > _______________________________________________ > intel-gvt-dev mailing list > intel-gvt-dev@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev

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On Tue, Apr 23, 2019 at 05:59:32PM +0800, Cornelia Huck wrote:

On Fri, 19 Apr 2019 04:35:04 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

device version attribute in mdev sysfs is used by user space software (e.g. libvirt) to query device compatibility for live migration of VFIO mdev devices. This attribute is mandatory if a mdev device supports live migration.

It consists of two parts: common part and vendor proprietary part. common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). vendor proprietary part: this part is varied in length. vendor driver can specify any string to identify a device.

When reading this attribute, it should show device version string of the device of type <type-id>. If a device does not support live migration, it should return errno.

It might make more sense if the driver does not register the attribute for the device in that case at all.

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When writing a string to this attribute, it returns errno for incompatibility or returns written string length in compatibility case. If a device does not support live migration, it always returns errno.

For user space software to use: 1. Before starting live migration, user space software first reads source side mdev device's version. e.g. "#cat \ /sys/bus/pci/devices/0000\:00\:02.0/5ac1fb20-2bbf-4842-bb7e-36c58c3be9cd/mdev_type/version" 00028086-193b-i915-GVTg_V5_4

2. Then, user space software writes the source side returned version string to device version attribute in target side, and checks the return value. If a negative errno is returned in the target side, then mdev devices in source and target sides are not compatible; If a positive number is returned and it equals to the length of written string, then the two mdev devices in source and target side are compatible. e.g. (a) compatibility case "# echo 00028086-193b-i915-GVTg_V5_4 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version"

(b) incompatibility case "#echo 00028086-193b-i915-GVTg_V5_1 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version" -bash: echo: write error: Invalid argument

3. if two mdev devices are compatible, user space software can start live migration, and vice versa.

Note: if a mdev device does not support live migration, it either does not provide a version attribute, or always returns errno when its version attribute is read/written.

Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Erik Skultety <eskultet@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Cornelia Huck <cohuck@redhat.com> Cc: "Tian, Kevin" <kevin.tian@intel.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: "Wang, Zhi A" <zhi.a.wang@intel.com> Cc: Neo Jia <cjia@nvidia.com> Cc: Kirti Wankhede <kwankhede@nvidia.com>

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com> --- Documentation/vfio-mediated-device.txt | 36 ++++++++++++++++++++++++++ samples/vfio-mdev/mbochs.c | 17 ++++++++++++ samples/vfio-mdev/mdpy.c | 16 ++++++++++++ samples/vfio-mdev/mtty.c | 16 ++++++++++++ 4 files changed, 85 insertions(+)

diff --git a/Documentation/vfio-mediated-device.txt b/Documentation/vfio-mediated-device.txt index c3f69bcaf96e..bc28471c0667 100644 --- a/Documentation/vfio-mediated-device.txt +++ b/Documentation/vfio-mediated-device.txt @@ -202,6 +202,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | | |--- create @@ -209,6 +210,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | |--- create @@ -216,6 +218,7 @@ Directories and files under the sysfs for Each Physical Device | |--- available_instances | |--- device_api | |--- description + | |--- version | |--- [devices]

* [mdev_supported_types] @@ -225,6 +228,8 @@ Directories and files under the sysfs for Each Physical Device [<type-id>], device_api, and available_instances are mandatory attributes that should be provided by vendor driver.

+ version is a mandatory attribute if a mdev device supports live migration.

What about "An mdev device wishing to support live migration must provide the version attribute."? yes, I just want to keep consistent with the line above it " [<type-id>], device_api, and available_instances are mandatory attributes

yes. what about rephrase like this: " When reading this attribute, it should show device version string of the device of type <type-id>. If a device does not support live migration, it has two choices: 1. do not register this version attribute 2. return -ENODEV on rw this version attribute Choice 1 is preferred. " that should be provided by vendor driver." what about below one? "version is a mandatory attribute if a mdev device wishing to support live migration."

...

+ * [<type-id>]

The [<type-id>] name is created by adding the device driver string as a prefix @@ -246,6 +251,35 @@ Directories and files under the sysfs for Each Physical Device This attribute should show the number of devices of type <type-id> that can be created.

+* version + + This attribute is rw. It is used to check whether two devices are compatible + for live migration. If this attribute is missing, then the corresponding mdev + device is regarded as not supporting live migration. + + It consists of two parts: common part and vendor proprietary part. + common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies + device type. e.g., for pci device, it is + "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). + vendor proprietary part: this part is varied in length. vendor driver can + specify any string to identify a device. + + When reading this attribute, it should show device version string of the device + of type <type-id>. If a device does not support live migration, it should + return errno. + When writing a string to this attribute, it returns errno for incompatibility + or returns written string length in compatibility case. If a device does not + support live migration, it always returns errno.

I'm not sure whether a device that does not support live migration should expose this attribute in the first place. Or is that to cover cases where a driver supports live migration only for some of the devices it supports? yes, driver returning error code is to cover the cases where only part of devices it supports can be migrated.

Also, I'm not sure if a string that has to be parsed is a good idea... is this 'version' attribute supposed to convey some human-readable information as well? The procedure you describe for compatibility checking does the checking within the vendor driver which I would expect to have a table/rules for that anyway. right. if a vendor driver has the confidence to migrate between devices of diffent platform or mdev types, it can maintain a compatibility table for that purpose. That's the reason why we would leave the compatibility check to vendor driver. vendor driver can freely choose its own complicated way to decide which device is migratable to which device.

I think you should also specify which errno writing an incompatible id is supposed to return (probably best something different than if the device does not support live migration at all, if we stick with creating the attribute in that case.) Agree. I'll define it clearly in next revison.

Thanks Yan

...

+ + for example. + # cat \ + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_2/version + 00028086-193b-i915-GVTg_V5_2 + + #echo 00028086-193b-i915-GVTg_V5_2 > \ + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_4/version + -bash: echo: write error: Invalid argument + * [device]

This directory contains links to the devices of type <type-id> that have been

---

intel-gvt-dev mailing list intel-gvt-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev

On Wed, Apr 24, 2019 at 03:56:24PM +0800, Cornelia Huck wrote:

On Tue, 23 Apr 2019 23:10:37 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

On Tue, Apr 23, 2019 at 05:59:32PM +0800, Cornelia Huck wrote:

...

On Fri, 19 Apr 2019 04:35:04 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

device version attribute in mdev sysfs is used by user space software (e.g. libvirt) to query device compatibility for live migration of VFIO mdev devices. This attribute is mandatory if a mdev device supports live migration.

It consists of two parts: common part and vendor proprietary part. common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). vendor proprietary part: this part is varied in length. vendor driver can specify any string to identify a device.

When reading this attribute, it should show device version string of the device of type <type-id>. If a device does not support live migration, it should return errno.

It might make more sense if the driver does not register the attribute for the device in that case at all.

yes. what about rephrase like this: " When reading this attribute, it should show device version string of the device of type <type-id>. If a device does not support live migration, it has two choices: 1. do not register this version attribute 2. return -ENODEV on rw this version attribute

"return -ENODEV when accessing the version attribute" ? Yeah, this one is better, thanks :)

...

Choice 1 is preferred. "

...

...

When writing a string to this attribute, it returns errno for incompatibility or returns written string length in compatibility case. If a device does not support live migration, it always returns errno.

For user space software to use: 1. Before starting live migration, user space software first reads source side mdev device's version. e.g. "#cat \ /sys/bus/pci/devices/0000\:00\:02.0/5ac1fb20-2bbf-4842-bb7e-36c58c3be9cd/mdev_type/version" 00028086-193b-i915-GVTg_V5_4

2. Then, user space software writes the source side returned version string to device version attribute in target side, and checks the return value. If a negative errno is returned in the target side, then mdev devices in source and target sides are not compatible; If a positive number is returned and it equals to the length of written string, then the two mdev devices in source and target side are compatible. e.g. (a) compatibility case "# echo 00028086-193b-i915-GVTg_V5_4 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version"

(b) incompatibility case "#echo 00028086-193b-i915-GVTg_V5_1 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version" -bash: echo: write error: Invalid argument

3. if two mdev devices are compatible, user space software can start live migration, and vice versa.

Note: if a mdev device does not support live migration, it either does not provide a version attribute, or always returns errno when its version attribute is read/written.

Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Erik Skultety <eskultet@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Cornelia Huck <cohuck@redhat.com> Cc: "Tian, Kevin" <kevin.tian@intel.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: "Wang, Zhi A" <zhi.a.wang@intel.com> Cc: Neo Jia <cjia@nvidia.com> Cc: Kirti Wankhede <kwankhede@nvidia.com>

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com> --- Documentation/vfio-mediated-device.txt | 36 ++++++++++++++++++++++++++ samples/vfio-mdev/mbochs.c | 17 ++++++++++++ samples/vfio-mdev/mdpy.c | 16 ++++++++++++ samples/vfio-mdev/mtty.c | 16 ++++++++++++ 4 files changed, 85 insertions(+)

diff --git a/Documentation/vfio-mediated-device.txt b/Documentation/vfio-mediated-device.txt index c3f69bcaf96e..bc28471c0667 100644 --- a/Documentation/vfio-mediated-device.txt +++ b/Documentation/vfio-mediated-device.txt @@ -202,6 +202,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | | |--- create @@ -209,6 +210,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | |--- create @@ -216,6 +218,7 @@ Directories and files under the sysfs for Each Physical Device | |--- available_instances | |--- device_api | |--- description + | |--- version | |--- [devices]

* [mdev_supported_types] @@ -225,6 +228,8 @@ Directories and files under the sysfs for Each Physical Device [<type-id>], device_api, and available_instances are mandatory attributes that should be provided by vendor driver.

+ version is a mandatory attribute if a mdev device supports live migration.

What about "An mdev device wishing to support live migration must provide the version attribute."? yes, I just want to keep consistent with the line above it " [<type-id>], device_api, and available_instances are mandatory attributes that should be provided by vendor driver." what about below one? "version is a mandatory attribute if a mdev device wishing to support live migration."

My point is that an attribute is not mandatory if it can be left out :) (I'm not a native speaker, though; maybe this makes perfect sense after all?)

Maybe "version is a required attribute if live migration is supported for an mdev device"?

you are right, "mandatory" may bring some confusion. Maybe "vendor driver must provide version attribute for an mdev device wishing to support live migration." ? based on your first version :)

...

...

...

+ * [<type-id>]

The [<type-id>] name is created by adding the device driver string as a prefix @@ -246,6 +251,35 @@ Directories and files under the sysfs for Each Physical Device This attribute should show the number of devices of type <type-id> that can be created.

+* version + + This attribute is rw. It is used to check whether two devices are compatible + for live migration. If this attribute is missing, then the corresponding mdev + device is regarded as not supporting live migration. + + It consists of two parts: common part and vendor proprietary part. + common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies + device type. e.g., for pci device, it is + "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). + vendor proprietary part: this part is varied in length. vendor driver can + specify any string to identify a device. + + When reading this attribute, it should show device version string of the device + of type <type-id>. If a device does not support live migration, it should + return errno. + When writing a string to this attribute, it returns errno for incompatibility + or returns written string length in compatibility case. If a device does not + support live migration, it always returns errno.

I'm not sure whether a device that does not support live migration should expose this attribute in the first place. Or is that to cover cases where a driver supports live migration only for some of the devices it supports? yes, driver returning error code is to cover the cases where only part of devices it supports can be migrated.

...

Also, I'm not sure if a string that has to be parsed is a good idea... is this 'version' attribute supposed to convey some human-readable information as well? The procedure you describe for compatibility checking does the checking within the vendor driver which I would expect to have a table/rules for that anyway. right. if a vendor driver has the confidence to migrate between devices of diffent platform or mdev types, it can maintain a compatibility table for that purpose. That's the reason why we would leave the compatibility check to vendor driver. vendor driver can freely choose its own complicated way to decide which device is migratable to which device.

I think there are two scenarios here: - Migrating between different device types, which is unlikely to work, except in special cases. - Migrating between different versions of the same device type, which may work for some drivers/devices (and at least migrating to a newer version looks quite reasonable).

But both should be something that is decided by the individual driver; I hope we don't want to support migration between different drivers :-O

Can we make this a driver-defined format?

yes, this is indeed driver-defined format. Actually we define it into two parts: common part and vendor proprietary part. common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). vendor proprietary part: this part is varied in length. vendor driver can specify any string to identify a device. vendor proprietary part is defined by vendor driver. vendor driver can define any format it wishes to use. Also it is its own responsibility to ensure backward compatibility if it wants to update format definition in this part. So user space only needs to get source side's version string, and asks target side whether the two are compatible. The decision maker is the vendor driver:)

...

...

I think you should also specify which errno writing an incompatible id is supposed to return (probably best something different than if the device does not support live migration at all, if we stick with creating the attribute in that case.) Agree. I'll define it clearly in next revison.

Thanks!

On Tue, Apr 30, 2019 at 11:29:08PM +0800, Cornelia Huck wrote:

On Wed, 24 Apr 2019 04:15:58 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

On Wed, Apr 24, 2019 at 03:56:24PM +0800, Cornelia Huck wrote:

...

On Tue, 23 Apr 2019 23:10:37 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

On Tue, Apr 23, 2019 at 05:59:32PM +0800, Cornelia Huck wrote:

...

On Fri, 19 Apr 2019 04:35:04 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

...

...

...

...

@@ -225,6 +228,8 @@ Directories and files under the sysfs for Each Physical Device [<type-id>], device_api, and available_instances are mandatory attributes that should be provided by vendor driver.

+ version is a mandatory attribute if a mdev device supports live migration.

What about "An mdev device wishing to support live migration must provide the version attribute."? yes, I just want to keep consistent with the line above it " [<type-id>], device_api, and available_instances are mandatory attributes that should be provided by vendor driver." what about below one? "version is a mandatory attribute if a mdev device wishing to support live migration."

My point is that an attribute is not mandatory if it can be left out :) (I'm not a native speaker, though; maybe this makes perfect sense after all?)

Maybe "version is a required attribute if live migration is supported for an mdev device"?

you are right, "mandatory" may bring some confusion. Maybe "vendor driver must provide version attribute for an mdev device wishing to support live migration." ? based on your first version :)

"The vendor driver must provide the version attribute for any mdev device it wishes to support live migration for." ?

...

...

...

...

...

+ * [<type-id>]

The [<type-id>] name is created by adding the device driver string as a prefix @@ -246,6 +251,35 @@ Directories and files under the sysfs for Each Physical Device This attribute should show the number of devices of type <type-id> that can be created.

+* version + + This attribute is rw. It is used to check whether two devices are compatible + for live migration. If this attribute is missing, then the corresponding mdev + device is regarded as not supporting live migration. + + It consists of two parts: common part and vendor proprietary part. + common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies + device type. e.g., for pci device, it is + "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). + vendor proprietary part: this part is varied in length. vendor driver can + specify any string to identify a device. + + When reading this attribute, it should show device version string of the device + of type <type-id>. If a device does not support live migration, it should + return errno. + When writing a string to this attribute, it returns errno for incompatibility + or returns written string length in compatibility case. If a device does not + support live migration, it always returns errno.

I'm not sure whether a device that does not support live migration should expose this attribute in the first place. Or is that to cover cases where a driver supports live migration only for some of the devices it supports? yes, driver returning error code is to cover the cases where only part of devices it supports can be migrated.

...

Also, I'm not sure if a string that has to be parsed is a good idea... is this 'version' attribute supposed to convey some human-readable information as well? The procedure you describe for compatibility checking does the checking within the vendor driver which I would expect to have a table/rules for that anyway. right. if a vendor driver has the confidence to migrate between devices of diffent platform or mdev types, it can maintain a compatibility table for that purpose. That's the reason why we would leave the compatibility check to vendor driver. vendor driver can freely choose its own complicated way to decide which device is migratable to which device.

I think there are two scenarios here: - Migrating between different device types, which is unlikely to work, except in special cases. - Migrating between different versions of the same device type, which may work for some drivers/devices (and at least migrating to a newer version looks quite reasonable).

But both should be something that is decided by the individual driver; I hope we don't want to support migration between different drivers :-O

Can we make this a driver-defined format?

yes, this is indeed driver-defined format. Actually we define it into two parts: common part and vendor proprietary part. common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). vendor proprietary part: this part is varied in length. vendor driver can specify any string to identify a device.

vendor proprietary part is defined by vendor driver. vendor driver can define any format it wishes to use. Also it is its own responsibility to ensure backward compatibility if it wants to update format definition in this part.

So user space only needs to get source side's version string, and asks target side whether the two are compatible. The decision maker is the vendor driver:)

If I followed the discussion correctly, I think you plan to drop this format, don't you? I'd be happy if a vendor driver can use a simple number without any prefixes if it so chooses.

I also like the idea of renaming this "migration_version" so that it is clear we're dealing with versioning of the migration capability (and not a version of the device or so). hi Cornelia, sorry I just saw this mail after sending v2 of this patch set... yes, I dropped the common part and vendor driver now can define whatever it wishes to identify a device version. However, I don't agree to rename it to "migration_version", as it still may bring some kind of confusing with the migration version a vendor driver is using, e.g. vendor driver changes migration code and increases that migration version. In fact, what info we want to get from this attribute is whether this mdev device is compatible with another mdev device, which is tied to device, and not necessarily bound to migration.

do you think so? Thanks Yan

_______________________________________________ intel-gvt-dev mailing list intel-gvt-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev

On 4/30/19 11:29 AM, Cornelia Huck wrote:

On Wed, 24 Apr 2019 04:15:58 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

On Wed, Apr 24, 2019 at 03:56:24PM +0800, Cornelia Huck wrote:

...

On Tue, 23 Apr 2019 23:10:37 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

On Tue, Apr 23, 2019 at 05:59:32PM +0800, Cornelia Huck wrote:

...

On Fri, 19 Apr 2019 04:35:04 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

...

...

...

...

...

@@ -225,6 +228,8 @@ Directories and files under the sysfs for Each Physical Device [<type-id>], device_api, and available_instances are mandatory attributes that should be provided by vendor driver.

+ version is a mandatory attribute if a mdev device supports live migration.

What about "An mdev device wishing to support live migration must provide the version attribute."? yes, I just want to keep consistent with the line above it " [<type-id>], device_api, and available_instances are mandatory attributes that should be provided by vendor driver." what about below one? "version is a mandatory attribute if a mdev device wishing to support live migration."

My point is that an attribute is not mandatory if it can be left out :) (I'm not a native speaker, though; maybe this makes perfect sense after all?)

Maybe "version is a required attribute if live migration is supported for an mdev device"?

My two cents: This is the best of the suggestions Tony Krowiak

...

...

you are right, "mandatory" may bring some confusion. Maybe "vendor driver must provide version attribute for an mdev device wishing to support live migration." ? based on your first version :)

"The vendor driver must provide the version attribute for any mdev device it wishes to support live migration for." ?

...

...

...

...

...

+ * [<type-id>]

The [<type-id>] name is created by adding the device driver string as a prefix @@ -246,6 +251,35 @@ Directories and files under the sysfs for Each Physical Device This attribute should show the number of devices of type <type-id> that can be created.

+* version + + This attribute is rw. It is used to check whether two devices are compatible + for live migration. If this attribute is missing, then the corresponding mdev + device is regarded as not supporting live migration. + + It consists of two parts: common part and vendor proprietary part. + common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies + device type. e.g., for pci device, it is + "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). + vendor proprietary part: this part is varied in length. vendor driver can + specify any string to identify a device. + + When reading this attribute, it should show device version string of the device + of type <type-id>. If a device does not support live migration, it should + return errno. + When writing a string to this attribute, it returns errno for incompatibility + or returns written string length in compatibility case. If a device does not + support live migration, it always returns errno.

I'm not sure whether a device that does not support live migration should expose this attribute in the first place. Or is that to cover cases where a driver supports live migration only for some of the devices it supports? yes, driver returning error code is to cover the cases where only part of devices it supports can be migrated.

...

Also, I'm not sure if a string that has to be parsed is a good idea... is this 'version' attribute supposed to convey some human-readable information as well? The procedure you describe for compatibility checking does the checking within the vendor driver which I would expect to have a table/rules for that anyway. right. if a vendor driver has the confidence to migrate between devices of diffent platform or mdev types, it can maintain a compatibility table for that purpose. That's the reason why we would leave the compatibility check to vendor driver. vendor driver can freely choose its own complicated way to decide which device is migratable to which device.

I think there are two scenarios here: - Migrating between different device types, which is unlikely to work, except in special cases. - Migrating between different versions of the same device type, which may work for some drivers/devices (and at least migrating to a newer version looks quite reasonable).

But both should be something that is decided by the individual driver; I hope we don't want to support migration between different drivers :-O

Can we make this a driver-defined format?

yes, this is indeed driver-defined format. Actually we define it into two parts: common part and vendor proprietary part. common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). vendor proprietary part: this part is varied in length. vendor driver can specify any string to identify a device.

vendor proprietary part is defined by vendor driver. vendor driver can define any format it wishes to use. Also it is its own responsibility to ensure backward compatibility if it wants to update format definition in this part.

So user space only needs to get source side's version string, and asks target side whether the two are compatible. The decision maker is the vendor driver:)

If I followed the discussion correctly, I think you plan to drop this format, don't you? I'd be happy if a vendor driver can use a simple number without any prefixes if it so chooses.

I also like the idea of renaming this "migration_version" so that it is clear we're dealing with versioning of the migration capability (and not a version of the device or so).

-- libvir-list mailing list libvir-list@redhat.com https://www.redhat.com/mailman/listinfo/libvir-list

On Tue, 23 Apr 2019 11:39:39 +0100 Daniel P. Berrangé <berrange@redhat.com> wrote:

On Fri, Apr 19, 2019 at 04:35:04AM -0400, Yan Zhao wrote:

...

device version attribute in mdev sysfs is used by user space software (e.g. libvirt) to query device compatibility for live migration of VFIO mdev devices. This attribute is mandatory if a mdev device supports live migration.

It consists of two parts: common part and vendor proprietary part. common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). vendor proprietary part: this part is varied in length. vendor driver can specify any string to identify a device.

When reading this attribute, it should show device version string of the device of type <type-id>. If a device does not support live migration, it should return errno. When writing a string to this attribute, it returns errno for incompatibility or returns written string length in compatibility case. If a device does not support live migration, it always returns errno.

For user space software to use: 1. Before starting live migration, user space software first reads source side mdev device's version. e.g. "#cat \ /sys/bus/pci/devices/0000\:00\:02.0/5ac1fb20-2bbf-4842-bb7e-36c58c3be9cd/mdev_type/version" 00028086-193b-i915-GVTg_V5_4

2. Then, user space software writes the source side returned version string to device version attribute in target side, and checks the return value. If a negative errno is returned in the target side, then mdev devices in source and target sides are not compatible; If a positive number is returned and it equals to the length of written string, then the two mdev devices in source and target side are compatible. e.g. (a) compatibility case "# echo 00028086-193b-i915-GVTg_V5_4 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version"

(b) incompatibility case "#echo 00028086-193b-i915-GVTg_V5_1 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version" -bash: echo: write error: Invalid argument

What you have written here seems to imply that each mdev type is able to support many different versions at the same time. Writing a version into this sysfs file then chooses which of the many versions to actually use.

That's not actually what's being proposed here, reading the version attribute provides an opaque string. Writing the version attribute from a different system reports whether that version string is compatible for migration. IOW, we're not creating a device of a given version, we're only reporting if that version is compatible with this mdev. The version is intentionally opaque to allow vendor specific nuances, therefore it's rather impractical create the sort of version list requested below.

This is good as it allows for live migration across driver software upgrades.

A mgmt application may well want to know what versions are supported for an mdev type *before* starting a migration. A mgmt app can query all the 100's of hosts it knows and thus figure out which are valid to use as the target of a migration.

IOW, we want to avoid the ever hitting the incompatibility case in the first place, by only choosing to migrate to a host that we know is going to be compatible.

This is provided, the migration source reports a version string which can be queried against the version attribute on other hosts to insure compatibility prior to migration.

This would need some kind of way to report the full list of supported versions against the mdev supported types on the host.

This is not provided, matching versions are vendor specific.

...

3. if two mdev devices are compatible, user space software can start live migration, and vice versa.

Note: if a mdev device does not support live migration, it either does not provide a version attribute, or always returns errno when its version attribute is read/written.

Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Erik Skultety <eskultet@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Cornelia Huck <cohuck@redhat.com> Cc: "Tian, Kevin" <kevin.tian@intel.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: "Wang, Zhi A" <zhi.a.wang@intel.com> Cc: Neo Jia <cjia@nvidia.com> Cc: Kirti Wankhede <kwankhede@nvidia.com>

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com> --- Documentation/vfio-mediated-device.txt | 36 ++++++++++++++++++++++++++ samples/vfio-mdev/mbochs.c | 17 ++++++++++++ samples/vfio-mdev/mdpy.c | 16 ++++++++++++ samples/vfio-mdev/mtty.c | 16 ++++++++++++ 4 files changed, 85 insertions(+)

diff --git a/Documentation/vfio-mediated-device.txt b/Documentation/vfio-mediated-device.txt index c3f69bcaf96e..bc28471c0667 100644 --- a/Documentation/vfio-mediated-device.txt +++ b/Documentation/vfio-mediated-device.txt @@ -202,6 +202,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | | |--- create @@ -209,6 +210,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | |--- create @@ -216,6 +218,7 @@ Directories and files under the sysfs for Each Physical Device | |--- available_instances | |--- device_api | |--- description + | |--- version | |--- [devices]

* [mdev_supported_types] @@ -225,6 +228,8 @@ Directories and files under the sysfs for Each Physical Device [<type-id>], device_api, and available_instances are mandatory attributes that should be provided by vendor driver.

+ version is a mandatory attribute if a mdev device supports live migration. + * [<type-id>]

The [<type-id>] name is created by adding the device driver string as a prefix @@ -246,6 +251,35 @@ Directories and files under the sysfs for Each Physical Device This attribute should show the number of devices of type <type-id> that can be created.

+* version + + This attribute is rw. It is used to check whether two devices are compatible + for live migration. If this attribute is missing, then the corresponding mdev + device is regarded as not supporting live migration. + + It consists of two parts: common part and vendor proprietary part. + common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies + device type. e.g., for pci device, it is + "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). + vendor proprietary part: this part is varied in length. vendor driver can + specify any string to identify a device. + + When reading this attribute, it should show device version string of the device + of type <type-id>. If a device does not support live migration, it should + return errno. + When writing a string to this attribute, it returns errno for incompatibility + or returns written string length in compatibility case. If a device does not + support live migration, it always returns errno. + + for example. + # cat \ + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_2/version + 00028086-193b-i915-GVTg_V5_2 + + #echo 00028086-193b-i915-GVTg_V5_2 > \ + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_4/version + -bash: echo: write error: Invalid argument +

IIUC this path is against the physical device. IOW, the mgmt app would have to first write to the "version" file to choose a version, and then write to the "create" file to actually create an virtual device. This has the obvious concurrency problem if multiple devices are being created at the same time and distinct versions for each device are required. There would need to be a locking scheme defined to ensure safety.

"Create a device of a given version" is not an intended feature of this interface aiui. Writing the version attribute only indicates migration compatibility with a binary result.

Wouldn't it be better if we can pass the desired version when we write to the "create" file, so that we avoid any concurrent usage problems. "version" could be just a read-only file with a *list* of supported versions.

eg

$ cat /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_4/version 5.0 5.1 5.2

$ echo "83b8f4f2-509f-382f-3c1e-e6bfe0fa1001;version=5.2" > /sys/devices/virtual/mtty/mtty/mdev_supported_types/mtty-2/create

This is reminiscent of the proposed aggregation support, but again, this sort of feature is not intended here. It's no expected that any vendor driver would support creating device types of different versions, but they may support migration from different versions. Thanks, Alex

On Wed, Apr 24, 2019 at 05:10:43PM +0800, Christophe de Dinechin wrote:

...

On 23 Apr 2019, at 12:39, Daniel P. Berrangé <berrange@redhat.com> wrote:

On Fri, Apr 19, 2019 at 04:35:04AM -0400, Yan Zhao wrote:

...

device version attribute in mdev sysfs is used by user space software (e.g. libvirt) to query device compatibility for live migration of VFIO mdev devices. This attribute is mandatory if a mdev device supports live migration.

It consists of two parts: common part and vendor proprietary part. common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). vendor proprietary part: this part is varied in length. vendor driver can specify any string to identify a device.

When reading this attribute, it should show device version string of the device of type <type-id>. If a device does not support live migration, it should return errno. When writing a string to this attribute, it returns errno for incompatibility or returns written string length in compatibility case. If a device does not support live migration, it always returns errno.

For user space software to use: 1. Before starting live migration, user space software first reads source side mdev device's version. e.g. "#cat \ /sys/bus/pci/devices/0000\:00\:02.0/5ac1fb20-2bbf-4842-bb7e-36c58c3be9cd/mdev_type/version" 00028086-193b-i915-GVTg_V5_4

2. Then, user space software writes the source side returned version string to device version attribute in target side, and checks the return value. If a negative errno is returned in the target side, then mdev devices in source and target sides are not compatible; If a positive number is returned and it equals to the length of written string, then the two mdev devices in source and target side are compatible. e.g. (a) compatibility case "# echo 00028086-193b-i915-GVTg_V5_4 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version"

(b) incompatibility case "#echo 00028086-193b-i915-GVTg_V5_1 > /sys/bus/pci/devices/0000\:00\:02.0/882cc4da-dede-11e7-9180-078a62063ab1/mdev_type/version" -bash: echo: write error: Invalid argument

What you have written here seems to imply that each mdev type is able to support many different versions at the same time. Writing a version into this sysfs file then chooses which of the many versions to actually use.

This is good as it allows for live migration across driver software upgrades.

A mgmt application may well want to know what versions are supported for an mdev type *before* starting a migration. A mgmt app can query all the 100's of hosts it knows and thus figure out which are valid to use as the target of a migration.

IOW, we want to avoid the ever hitting the incompatibility case in the first place, by only choosing to migrate to a host that we know is going to be compatible.

This would need some kind of way to report the full list of supported versions against the mdev supported types on the host.

...

3. if two mdev devices are compatible, user space software can start live migration, and vice versa.

Note: if a mdev device does not support live migration, it either does not provide a version attribute, or always returns errno when its version attribute is read/written.

Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Erik Skultety <eskultet@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Cornelia Huck <cohuck@redhat.com> Cc: "Tian, Kevin" <kevin.tian@intel.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: "Wang, Zhi A" <zhi.a.wang@intel.com> Cc: Neo Jia <cjia@nvidia.com> Cc: Kirti Wankhede <kwankhede@nvidia.com>

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com> --- Documentation/vfio-mediated-device.txt | 36 ++++++++++++++++++++++++++ samples/vfio-mdev/mbochs.c | 17 ++++++++++++ samples/vfio-mdev/mdpy.c | 16 ++++++++++++ samples/vfio-mdev/mtty.c | 16 ++++++++++++ 4 files changed, 85 insertions(+)

diff --git a/Documentation/vfio-mediated-device.txt b/Documentation/vfio-mediated-device.txt index c3f69bcaf96e..bc28471c0667 100644 --- a/Documentation/vfio-mediated-device.txt +++ b/Documentation/vfio-mediated-device.txt @@ -202,6 +202,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | | |--- create @@ -209,6 +210,7 @@ Directories and files under the sysfs for Each Physical Device | | |--- available_instances | | |--- device_api | | |--- description + | | |--- version | | |--- [devices] | |--- [<type-id>] | |--- create @@ -216,6 +218,7 @@ Directories and files under the sysfs for Each Physical Device | |--- available_instances | |--- device_api | |--- description + | |--- version | |--- [devices]

* [mdev_supported_types] @@ -225,6 +228,8 @@ Directories and files under the sysfs for Each Physical Device [<type-id>], device_api, and available_instances are mandatory attributes that should be provided by vendor driver.

+ version is a mandatory attribute if a mdev device supports live migration. + * [<type-id>]

The [<type-id>] name is created by adding the device driver string as a prefix @@ -246,6 +251,35 @@ Directories and files under the sysfs for Each Physical Device This attribute should show the number of devices of type <type-id> that can be created.

+* version + + This attribute is rw. It is used to check whether two devices are compatible + for live migration. If this attribute is missing, then the corresponding mdev + device is regarded as not supporting live migration. + + It consists of two parts: common part and vendor proprietary part. + common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies + device type. e.g., for pci device, it is + "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). + vendor proprietary part: this part is varied in length. vendor driver can + specify any string to identify a device. + + When reading this attribute, it should show device version string of the device + of type <type-id>. If a device does not support live migration, it should + return errno. + When writing a string to this attribute, it returns errno for incompatibility + or returns written string length in compatibility case. If a device does not + support live migration, it always returns errno. + + for example. + # cat \ + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_2/version + 00028086-193b-i915-GVTg_V5_2 + + #echo 00028086-193b-i915-GVTg_V5_2 > \ + /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_4/version + -bash: echo: write error: Invalid argument +

IIUC this path is against the physical device. IOW, the mgmt app would have to first write to the "version" file to choose a version, and then write to the "create" file to actually create an virtual device. This has the obvious concurrency problem if multiple devices are being created at the same time and distinct versions for each device are required. There would need to be a locking scheme defined to ensure safety.

Wouldn't it be better if we can pass the desired version when we write to the "create" file, so that we avoid any concurrent usage problems. "version" could be just a read-only file with a *list* of supported versions.

eg

$ cat /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_4/version 5.0 5.1 5.2

$ echo "83b8f4f2-509f-382f-3c1e-e6bfe0fa1001;version=5.2" > /sys/devices/virtual/mtty/mtty/mdev_supported_types/mtty-2/create

I read Alex’s comment that creating an mdev with a specific version is not the intent here. However…

- If the goal is just to check compatibility with migration data, then I think the name should be more explicit, e.g. migration_version instead of version. Otherwise, I read the intent the way Daniel did.

hi Christophe, you are right, this "version" is not for creating mdev device. It is to describe a mdev clearly (therefore it may include information about an mdev's parent device). As a result, it can be leveraged by migration -- before starting migration, user space software can check if two mdev devices are compatible for migration. (of course, this check is shifting to vendor driver by writing one mdev's version string to another mdev's version node and checking the result). Compared to renaming it to migration_version, I would like to describe its usage more clearly in doc. Thanks for your input:) Yan

- If we want to provide a list of versions and make it possible to create instances based on a version, I would rather use a directory structure for that, i.e. (replacing cat with ls):

$ ls /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_4/version 5.0 5.1 5.2

where each version is a directory that has its own available_instances, device_api, description, create, …

$ echo 83b8f4f2-509f-382f-3c1e-e6bfe0fa1001 > /sys/bus/pci/devices/0000\:00\:02.0/mdev_supported_types/i915-GVTg_V5_4/version/5.1/create

In addition to not having the problem of two consecutive writes to distinct files, I can imagine contrived cases where available_instances might depend on the version…

Thanks Christophe

...

Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|

On 2019.04.19 04:35:59 -0400, Yan Zhao wrote:

This feature implements the version attribute for Intel's vGPU mdev devices.

version attribute is rw. It is queried by userspace software like libvirt to check whether two vGPUs are compatible for live migration.

It consists of two parts: common part and vendor proprietary part. common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). vendor proprietary part: this part is varied in length. vendor driver can specify any string to identify a device.

For Intel vGPU of gen8 and gen9, the vendor proprietary part currently consists of 2 fields: "device id" + "mdev type".

Reading from a vGPU's version attribute, a string is returned in below format: 00028086-<device id>-<mdev type>. e.g. 00028086-193b-i915-GVTg_V5_2.

Writing a string to a vGPU's version attribute will trigger GVT to check whether a vGPU identified by the written string is compatible with current vGPU owning this version attribute. errno is returned if the two vGPUs are incompatible. The length of written string is returned in compatible case.

For other platforms, and for GVT not supporting vGPU live migration feature, errnos are returned when read/write of mdev devices' version attributes.

For old GVT versions where no version attributes exposed in sysfs, it is regarded as not supporting vGPU live migration.

For future platforms, besides the current 2 fields in vendor proprietary part, more fields may be added to identify Intel vGPU well for live migration purpose.

Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Erik Skultety <eskultet@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Cornelia Huck <cohuck@redhat.com> Cc: "Tian, Kevin" <kevin.tian@intel.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: "Wang, Zhi A" <zhi.a.wang@intel.com> c: Neo Jia <cjia@nvidia.com> Cc: Kirti Wankhede <kwankhede@nvidia.com>

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com> --- drivers/gpu/drm/i915/gvt/Makefile | 2 +- drivers/gpu/drm/i915/gvt/device_version.c | 94 +++++++++++++++++++++++ drivers/gpu/drm/i915/gvt/gvt.c | 55 +++++++++++++ drivers/gpu/drm/i915/gvt/gvt.h | 6 ++ 4 files changed, 156 insertions(+), 1 deletion(-) create mode 100644 drivers/gpu/drm/i915/gvt/device_version.c

diff --git a/drivers/gpu/drm/i915/gvt/Makefile b/drivers/gpu/drm/i915/gvt/Makefile index 271fb46d4dd0..54e209a23899 100644 --- a/drivers/gpu/drm/i915/gvt/Makefile +++ b/drivers/gpu/drm/i915/gvt/Makefile @@ -3,7 +3,7 @@ GVT_DIR := gvt GVT_SOURCE := gvt.o aperture_gm.o handlers.o vgpu.o trace_points.o firmware.o \ interrupt.o gtt.o cfg_space.o opregion.o mmio.o display.o edid.o \ execlist.o scheduler.o sched_policy.o mmio_context.o cmd_parser.o debugfs.o \ - fb_decoder.o dmabuf.o page_track.o + fb_decoder.o dmabuf.o page_track.o device_version.o

ccflags-y += -I$(src) -I$(src)/$(GVT_DIR) i915-y += $(addprefix $(GVT_DIR)/, $(GVT_SOURCE)) diff --git a/drivers/gpu/drm/i915/gvt/device_version.c b/drivers/gpu/drm/i915/gvt/device_version.c new file mode 100644 index 000000000000..c64010d2bc54 --- /dev/null +++ b/drivers/gpu/drm/i915/gvt/device_version.c @@ -0,0 +1,94 @@ +/* + * Copyright(c) 2011-2017 Intel Corporation. All rights reserved. + * + * Permission is hereby granted, free of charge, to any person obtaining a + * copy of this software and associated documentation files (the "Software"), + * to deal in the Software without restriction, including without limitation + * the rights to use, copy, modify, merge, publish, distribute, sublicense, + * and/or sell copies of the Software, and to permit persons to whom the + * Software is furnished to do so, subject to the following conditions: + * + * The above copyright notice and this permission notice (including the next + * paragraph) shall be included in all copies or substantial portions of the + * Software. + * + * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR + * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, + * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL + * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER + * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, + * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE + * SOFTWARE. + */ +#include <linux/vfio.h> +#include "i915_drv.h" + +#define GVT_VFIO_DEVICE_VENDOR_ID ((0x8086) | \ + ((VFIO_DEVICE_FLAGS_PCI & 0xff) << 16)) + +#define GVT_DEVICE_VERSION_COMMON_LEN 0x8 +#define GVT_DEVICE_VERSION_DEVICE_ID_LEN 0x4 + +static bool is_compatible(const char *self, const char *remote) +{ + if (strlen(remote) != strlen(self)) + return false; + + return (strncmp(self, remote, strlen(self))) ? false : true; +} + +ssize_t intel_gvt_get_vfio_device_version_len(struct drm_i915_private *dev_priv) +{ + if (!IS_GEN(dev_priv, 8) && !IS_GEN(dev_priv, 9)) + return -ENODEV; + + return PAGE_SIZE; +} + +ssize_t intel_gvt_get_vfio_device_version(struct drm_i915_private *dev_priv, + char *buf, const char *mdev_type) +{ + int cnt = 0, ret = 0; + const char *str = NULL; + + /* currently only gen8 & gen9 are supported */ + if (!IS_GEN(dev_priv, 8) && !IS_GEN(dev_priv, 9)) + return -ENODEV; + + /* first 32 bit common part specifying vendor id and it's a pci + * device + */ + cnt = snprintf(buf, GVT_DEVICE_VERSION_COMMON_LEN + 1, + "%08x", GVT_VFIO_DEVICE_VENDOR_ID); + buf += cnt; + ret += cnt; + + /* vendor proprietary part: device id + mdev type */ + /* device id */ + cnt = snprintf(buf, GVT_DEVICE_VERSION_DEVICE_ID_LEN + 2, + "-%04x", INTEL_DEVID(dev_priv)); + buf += cnt; + ret += cnt; + + /* mdev type */ + str = mdev_type; + cnt = snprintf(buf, strlen(str) + 3, "-%s\n", mdev_type); + buf += cnt; + ret += cnt; + + return ret; +} + +ssize_t intel_gvt_check_vfio_device_version(struct drm_i915_private *dev_priv, + const char *self, const char *remote) +{ + + /* currently only gen8 & gen9 are supported */ + if (!IS_GEN(dev_priv, 8) && !IS_GEN(dev_priv, 9)) + return -ENODEV; + + if (!is_compatible(self, remote)) + return -EINVAL; + + return 0; +} diff --git a/drivers/gpu/drm/i915/gvt/gvt.c b/drivers/gpu/drm/i915/gvt/gvt.c index 43f4242062dd..e720465b93d8 100644 --- a/drivers/gpu/drm/i915/gvt/gvt.c +++ b/drivers/gpu/drm/i915/gvt/gvt.c @@ -105,14 +105,69 @@ static ssize_t description_show(struct kobject *kobj, struct device *dev, type->weight); }

+static ssize_t version_show(struct kobject *kobj, struct device *dev, + char *buf) +{ +#ifdef GVT_MIGRATION_VERSION + struct drm_i915_private *i915 = kdev_to_i915(dev); + const char *mdev_type = kobject_name(kobj); + + return intel_gvt_get_vfio_device_version(i915, buf, mdev_type); +#else + /* do not support live migration */ + return -EINVAL; +#endif +} + +static ssize_t version_store(struct kobject *kobj, struct device *dev, + const char *buf, size_t count) +{ +#ifdef GVT_MIGRATION_VERSION + char *remote = NULL, *self = NULL; + int len, ret = 0; + struct drm_i915_private *i915 = kdev_to_i915(dev); + const char *mdev_type = kobject_name(kobj); + + len = intel_gvt_get_vfio_device_version_len(i915); + if (len < 0) + return len; + + self = kmalloc(len, GFP_KERNEL); + if (!self) + return -ENOMEM; + + ret = intel_gvt_get_vfio_device_version(i915, self, mdev_type); + if (ret < 0) + goto out; +

device version string should be allocated and specified during device instance setup instead of version attribute r/w time.

+ remote = kstrndup(buf, count, GFP_KERNEL); + if (!remote) { + ret = -ENOMEM; + goto out; + } + + ret = intel_gvt_check_vfio_device_version(i915, self, remote); + +out: + kfree(self); + kfree(remote); + return (ret < 0 ? ret : count); +#else + /* do not support live migration */ + return -EINVAL; +#endif +} + static MDEV_TYPE_ATTR_RO(available_instances); static MDEV_TYPE_ATTR_RO(device_api); static MDEV_TYPE_ATTR_RO(description); +static MDEV_TYPE_ATTR_RW(version);

static struct attribute *gvt_type_attrs[] = { &mdev_type_attr_available_instances.attr, &mdev_type_attr_device_api.attr, &mdev_type_attr_description.attr, + &mdev_type_attr_version.attr, NULL, };

diff --git a/drivers/gpu/drm/i915/gvt/gvt.h b/drivers/gpu/drm/i915/gvt/gvt.h index f5a328b5290a..4062f6b26acf 100644 --- a/drivers/gpu/drm/i915/gvt/gvt.h +++ b/drivers/gpu/drm/i915/gvt/gvt.h @@ -687,6 +687,12 @@ void intel_gvt_debugfs_remove_vgpu(struct intel_vgpu *vgpu); int intel_gvt_debugfs_init(struct intel_gvt *gvt); void intel_gvt_debugfs_clean(struct intel_gvt *gvt);

+ssize_t intel_gvt_get_vfio_device_version(struct drm_i915_private *i915, + char *buf, const char *mdev_type); +ssize_t intel_gvt_check_vfio_device_version(struct drm_i915_private *dev_priv, + const char *self, const char *remote); +ssize_t +intel_gvt_get_vfio_device_version_len(struct drm_i915_private *dev_priv);

#include "trace.h" #include "mpt.h" -- 2.17.1

_______________________________________________ intel-gvt-dev mailing list intel-gvt-dev@lists.freedesktop.org https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev

-- Open Source Technology Center, Intel ltd. $gpg --keyserver wwwkeys.pgp.net --recv-keys 4D781827

On Fri, 19 Apr 2019 04:35:59 -0400 Yan Zhao <yan.y.zhao@intel.com> wrote:

This feature implements the version attribute for Intel's vGPU mdev devices.

version attribute is rw. It is queried by userspace software like libvirt to check whether two vGPUs are compatible for live migration.

It consists of two parts: common part and vendor proprietary part. common part: 32 bit. lower 16 bits is vendor id and higher 16 bits identifies device type. e.g., for pci device, it is "pci vendor id" | (VFIO_DEVICE_FLAGS_PCI << 16). vendor proprietary part: this part is varied in length. vendor driver can specify any string to identify a device.

For Intel vGPU of gen8 and gen9, the vendor proprietary part currently consists of 2 fields: "device id" + "mdev type".

Reading from a vGPU's version attribute, a string is returned in below format: 00028086-<device id>-<mdev type>. e.g. 00028086-193b-i915-GVTg_V5_2.

Writing a string to a vGPU's version attribute will trigger GVT to check whether a vGPU identified by the written string is compatible with current vGPU owning this version attribute. errno is returned if the two vGPUs are incompatible. The length of written string is returned in compatible case.

For other platforms, and for GVT not supporting vGPU live migration feature, errnos are returned when read/write of mdev devices' version attributes.

For old GVT versions where no version attributes exposed in sysfs, it is regarded as not supporting vGPU live migration.

For future platforms, besides the current 2 fields in vendor proprietary part, more fields may be added to identify Intel vGPU well for live migration purpose.

Cc: Alex Williamson <alex.williamson@redhat.com> Cc: Erik Skultety <eskultet@redhat.com> Cc: "Dr. David Alan Gilbert" <dgilbert@redhat.com> Cc: Cornelia Huck <cohuck@redhat.com> Cc: "Tian, Kevin" <kevin.tian@intel.com> Cc: Zhenyu Wang <zhenyuw@linux.intel.com> Cc: "Wang, Zhi A" <zhi.a.wang@intel.com> c: Neo Jia <cjia@nvidia.com> Cc: Kirti Wankhede <kwankhede@nvidia.com>

Signed-off-by: Yan Zhao <yan.y.zhao@intel.com> --- drivers/gpu/drm/i915/gvt/Makefile | 2 +- drivers/gpu/drm/i915/gvt/device_version.c | 94 +++++++++++++++++++++++ drivers/gpu/drm/i915/gvt/gvt.c | 55 +++++++++++++ drivers/gpu/drm/i915/gvt/gvt.h | 6 ++ 4 files changed, 156 insertions(+), 1 deletion(-) create mode 100644 drivers/gpu/drm/i915/gvt/device_version.c

(...)

+static bool is_compatible(const char *self, const char *remote) +{ + if (strlen(remote) != strlen(self)) + return false; + + return (strncmp(self, remote, strlen(self))) ? false : true; +} + +ssize_t intel_gvt_get_vfio_device_version_len(struct drm_i915_private *dev_priv) +{ + if (!IS_GEN(dev_priv, 8) && !IS_GEN(dev_priv, 9)) + return -ENODEV; + + return PAGE_SIZE; +} + +ssize_t intel_gvt_get_vfio_device_version(struct drm_i915_private *dev_priv, + char *buf, const char *mdev_type) +{ + int cnt = 0, ret = 0; + const char *str = NULL; + + /* currently only gen8 & gen9 are supported */ + if (!IS_GEN(dev_priv, 8) && !IS_GEN(dev_priv, 9)) + return -ENODEV; + + /* first 32 bit common part specifying vendor id and it's a pci + * device + */ + cnt = snprintf(buf, GVT_DEVICE_VERSION_COMMON_LEN + 1, + "%08x", GVT_VFIO_DEVICE_VENDOR_ID); + buf += cnt; + ret += cnt; + + /* vendor proprietary part: device id + mdev type */ + /* device id */ + cnt = snprintf(buf, GVT_DEVICE_VERSION_DEVICE_ID_LEN + 2, + "-%04x", INTEL_DEVID(dev_priv)); + buf += cnt; + ret += cnt; + + /* mdev type */ + str = mdev_type; + cnt = snprintf(buf, strlen(str) + 3, "-%s\n", mdev_type); + buf += cnt; + ret += cnt; + + return ret; +}

Looking at this handling, it seems much easier to me to simply use a numeric value instead of a string: You don't have to build it via sprintf, there are generic functions for parsing a string input into a simple number, and you have more options for compatibility (e.g. "version must be between m and n" instead of an exact match). If you still need to encode the device id here, you should be able to easily do something like (device_id << 16) | migration_version -- do you think that could work?

+ +ssize_t intel_gvt_check_vfio_device_version(struct drm_i915_private *dev_priv, + const char *self, const char *remote) +{ + + /* currently only gen8 & gen9 are supported */ + if (!IS_GEN(dev_priv, 8) && !IS_GEN(dev_priv, 9)) + return -ENODEV; + + if (!is_compatible(self, remote)) + return -EINVAL;

I think the meaning of the error codes should really be standardized across vendor drivers, if we need a value for "this device does not support migration at all". (Your choices look reasonable for that.)

+ + return 0; +} diff --git a/drivers/gpu/drm/i915/gvt/gvt.c b/drivers/gpu/drm/i915/gvt/gvt.c index 43f4242062dd..e720465b93d8 100644 --- a/drivers/gpu/drm/i915/gvt/gvt.c +++ b/drivers/gpu/drm/i915/gvt/gvt.c @@ -105,14 +105,69 @@ static ssize_t description_show(struct kobject *kobj, struct device *dev, type->weight); }

+static ssize_t version_show(struct kobject *kobj, struct device *dev, + char *buf) +{ +#ifdef GVT_MIGRATION_VERSION + struct drm_i915_private *i915 = kdev_to_i915(dev); + const char *mdev_type = kobject_name(kobj); + + return intel_gvt_get_vfio_device_version(i915, buf, mdev_type); +#else + /* do not support live migration */ + return -EINVAL;

...but this looks inconsistent. I would expect -ENODEV here, same as for non-gen{8,9}. Or simply do not create the attribute at all in that case?

+#endif +} + +static ssize_t version_store(struct kobject *kobj, struct device *dev, + const char *buf, size_t count) +{ +#ifdef GVT_MIGRATION_VERSION + char *remote = NULL, *self = NULL; + int len, ret = 0; + struct drm_i915_private *i915 = kdev_to_i915(dev); + const char *mdev_type = kobject_name(kobj); + + len = intel_gvt_get_vfio_device_version_len(i915); + if (len < 0) + return len; + + self = kmalloc(len, GFP_KERNEL); + if (!self) + return -ENOMEM; + + ret = intel_gvt_get_vfio_device_version(i915, self, mdev_type); + if (ret < 0) + goto out; + + remote = kstrndup(buf, count, GFP_KERNEL); + if (!remote) { + ret = -ENOMEM; + goto out; + } + + ret = intel_gvt_check_vfio_device_version(i915, self, remote); + +out: + kfree(self); + kfree(remote); + return (ret < 0 ? ret : count); +#else + /* do not support live migration */ + return -EINVAL; +#endif +} + static MDEV_TYPE_ATTR_RO(available_instances); static MDEV_TYPE_ATTR_RO(device_api); static MDEV_TYPE_ATTR_RO(description); +static MDEV_TYPE_ATTR_RW(version);

static struct attribute *gvt_type_attrs[] = { &mdev_type_attr_available_instances.attr, &mdev_type_attr_device_api.attr, &mdev_type_attr_description.attr, + &mdev_type_attr_version.attr, NULL, };

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