[libvirt PATCH] nodedev: Handle inactive mdevs with the same UUID

[Boris Fiuczynski]

On 7/6/21 9:05 PM, Jonathon Jongsma wrote:
> Unfortunately, mdevctl supports defining more than one mdev with the
> same UUID as long as they have different parent devices. So we can't use
> the UUID alone as a way to uniquely identify these node devices. Append
> the parent name to ensure uniqueness. For example:
> 
>      Before: mdev_88a6b868_46bd_4015_8e5b_26107f82da38
>      After:  mdev_88a6b868_46bd_4015_8e5b_26107f82da38_0000_00_02_0
> 
> Resolves: https://bugzilla.redhat.com/show_bug.cgi?id=1979440
> 
> Signed-off-by: Jonathon Jongsma <jjongsma at redhat.com>
> ---
> QUESTION: Is there any expectation of stability in these device names? I'm not
> sure to what extent these changes might affect users. Given that support for
> persistent mdevs is fairly new, there are likely not many users yet.

People using mdevs with libvirt will certainly be impacted by this but I 
am not sure how many there are.

I am wondering if the scenario is even useful since I just tried it out 
and starting the second mdev with the uuid fails.

# mdevctl list -d
e60cef97-3f6b-485e-ac46-0520f9f66ac2 0.0.0033 vfio_ccw-io manual (active)
e60cef97-3f6b-485e-ac46-0520f9f66ac2 0.0.0034 vfio_ccw-io manual
# mdevctl start -u e60cef97-3f6b-485e-ac46-0520f9f66ac2 -p 0.0.0034
Device exists under different parent


> 
>   src/node_device/node_device_driver.c | 2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/src/node_device/node_device_driver.c b/src/node_device/node_device_driver.c
> index b4dd57e5f4..89dc704162 100644
> --- a/src/node_device/node_device_driver.c
> +++ b/src/node_device/node_device_driver.c
> @@ -1038,7 +1038,7 @@ nodeDeviceGetMdevctlListCommand(bool defined,
>   
>   static void mdevGenerateDeviceName(virNodeDeviceDef *dev)
>   {
> -    nodeDeviceGenerateName(dev, "mdev", dev->caps->data.mdev.uuid, NULL);
> +    nodeDeviceGenerateName(dev, "mdev", dev->caps->data.mdev.uuid, dev->parent);
>   }
>   
>   
> 


-- 
Mit freundlichen Grüßen/Kind regards
    Boris Fiuczynski

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