Re: [PATCH] virtio-gpu: get p2pdma distance

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

On Tue, Jan 14, 2025 at 06:16:13PM +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.
> 
> Signed-off-by: Julia Zhang <julia.zhang@amd.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/
> 
> Regards,
> Julia
> ---
>  device-types/gpu/description.tex | 29 +++++++++++++++++++++++++++++
>  1 file changed, 29 insertions(+)
> 

Reviewed-by: Matias Ezequiel Vara Larsen <mvaralar@redhat.com>