3:35 a.m.
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
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(a)redhat.com>
Cc: Erik Skultety <eskultet(a)redhat.com>
Cc: "Dr. David Alan Gilbert" <dgilbert(a)redhat.com>
Cc: Cornelia Huck <cohuck(a)redhat.com>
Cc: "Tian, Kevin" <kevin.tian(a)intel.com>
Cc: Zhenyu Wang <zhenyuw(a)linux.intel.com>
Cc: "Wang, Zhi A" <zhi.a.wang(a)intel.com>
Cc: Neo Jia <cjia(a)nvidia.com>
Cc: Kirti Wankhede <kwankhede(a)nvidia.com>
Signed-off-by: Yan Zhao <yan.y.zhao(a)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,
};
--
2.17.1