Re: [PATCH v2 1/1] virtio-gpu: get p2pdma distance

[Matias Ezequiel Vara Larsen <mvaralar@redhat.com>]

On Wed, Feb 26, 2025 at 05:27:54PM +0800, Julia Zhang wrote:
> PCI peer-to-peer DMA transaction may be used in guest for some scenes.
> For example, dGPU prime feature will let virtio-iGPU access to
> passthrough dGPU buffer.
> 
> To support P2P DMA transaction in guest, virtio-gpu needs to check the
> compatibility which is represented by p2pdma_distance. This defines a
> command VIRTIO_GPU_CMD_P2PDMA_DISTANCE to allow guest send virtual pci
> notation of two devices to host and get host physical p2pdma_distance
> of these two PCI devices.
> 
> Fixes:https://github.com/oasis-tcs/virtio-spec/issues/217
> Signed-off-by: Julia Zhang <julia.zhang@amd.com>
> Reviewed-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com>
> ---
> Hi all,
> 
> We are trying to implement dGPU prime feature in guest which will let
> virtio-iGPU read rendered data of passthrough dGPU. Before that, virtio gpu
> driver needs to get p2pdma_distance to check if P2P DMA transaction is
> possible or not.
> 
> To implement getting p2pdma_distance, QEMU needs to handle the command from
> guest with virtual pci notations of two PCI devices and send it to host
> kernel and return host physical distance back to guest.
> 
> So this defines the new command follow the suggestion in https:
> //lore.kernel.org/all/20241207105537.542441-4-julia.zhang@amd.com/
> 
> changes from v1:
>  - add issue link to commit msg
> 
> Regards,
> Julia
> ---

I think what is missing is to explicitly request a vote as is explained
in 2) at
https://github.com/oasis-tcs/virtio-spec/blob/master/README.md#use-of-github-issues.

Thanks, Matias