Re: [libvirt] [PATCH v3 1/2] vfio/mdev: add migration_version attribute for mdev device
On Tue, May 28, 2019 at 04:53:32PM +0800, Cornelia Huck wrote:
On Sun, 26 May 2019 23:43:42 -0400
Yan Zhao <yan.y.zhao(a)intel.com> wrote:
> migration_version attribute is used to check migration compatibility
> between two mdev device of the same mdev type.
s/device/devices/
yes... sorry and thanks :)
> The key is that it's rw and its data is opaque to
userspace.
>
> Userspace reads migration_version of mdev device at source side and
> writes the value to migration_version attribute of mdev device at target
> side. It judges migration compatibility according to whether the read
> and write operations succeed or fail.
>
> As this attribute is under mdev_type node, userspace is able to know
> whether two mdev devices are compatible before a mdev device is created.
>
> userspace needs to check whether the two mdev devices are of the same
> mdev type before checking the migration_version attribute. It also needs
> to check device creation parameters if aggregation is supported in
> future.
>
> __ userspace
> /\ \
> / \write
> / read \
> ________/__________ ___\|/_____________
> | migration_version | | migration_version |-->check migration
> --------------------- --------------------- compatibility
> mdev device A mdev device B
>
> 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>
> Cc: Daniel P. Berrangé <berrange(a)redhat.com>
> Cc: Christophe de Dinechin <dinechin(a)redhat.com>
>
> Signed-off-by: Yan Zhao <yan.y.zhao(a)intel.com>
>
> ---
> v3:
> 1. renamed version to migration_version
> (Christophe de Dinechin, Cornelia Huck, Alex Williamson)
> 2. let errno to be freely defined by vendor driver
> (Alex Williamson, Erik Skultety, Cornelia Huck, Dr. David Alan Gilbert)
> 3. let checking mdev_type be prerequisite of migration compatibility
> check. (Alex Williamson)
> 4. reworded example usage section.
> (most of this section came from Alex Williamson)
> 5. reworded attribute intention section (Cornelia Huck)
>
> v2:
> 1. added detailed intent and usage
> 2. made definition of version string completely private to vendor driver
> (Alex Williamson)
> 3. abandoned changes to sample mdev drivers (Alex Williamson)
> 4. mandatory --> optional (Cornelia Huck)
> 5. added description for errno (Cornelia Huck)
> ---
> Documentation/vfio-mediated-device.txt | 113 +++++++++++++++++++++++++
> 1 file changed, 113 insertions(+)
>
While I probably would have written a more compact description, your
version is fine with me as well.
Reviewed-by: Cornelia Huck <cohuck(a)redhat.com>
Thank you Cornelia!
_______________________________________________
intel-gvt-dev mailing list
intel-gvt-dev(a)lists.freedesktop.org
https://lists.freedesktop.org/mailman/listinfo/intel-gvt-dev