linux-kernel - Re: [RFC PATCH 1/3] virtio-gpu api: add blob userptr resource

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Message-ID: <a8bf6c8b-5ee5-4150-a9a2-75345fd07432@daynix.com>
Date: Mon, 3 Feb 2025 17:25:53 +0900
From: Akihiko Odaki <akihiko.odaki@...nix.com>
To: Honglei Huang <honglei1.huang@....com>,
 Gurchetan Singh <gurchetansingh@...omium.org>,
 Antonio Caggiano <quic_acaggian@...cinc.com>
Cc: Lingshan Zhu <Lingshan.Zhu@....com>,
 Demi Marie Obenour <demiobenour@...il.com>, Huang Rui <ray.huang@....com>,
 virtualization@...ts.linux-foundation.org, linux-kernel@...r.kernel.org,
 Dmitry Osipenko <dmitry.osipenko@...labora.com>,
 dri-devel@...ts.freedesktop.org, David Airlie <airlied@...hat.com>,
 Gerd Hoffmann <kraxel@...hat.com>, Chia-I Wu <olvaffe@...il.com>,
 Daniel Vetter <daniel.vetter@...ll.ch>
Subject: Re: [RFC PATCH 1/3] virtio-gpu api: add blob userptr resource

On 2024/12/20 19:04, Honglei Huang wrote:
> From: Honglei Huang <Honglei1.Huang@....com>
> 
> Add a new resource for blob resource, called userptr, used for let
> host access guest user space memory, to acquire a simple SVM features
> in virtio GPU.
> 
> - The capset VIRTIO_GPU_CAPSET_HSAKMT used for context init,
> in this series patches only HSAKMT context can use the userptr
> feature. HSAKMT is a GPU compute library in HSA stack, like
> the role libdrm in mesa stack.
> - New flag VIRTIO_GPU_BLOB_FLAG_USE_USERPTR used in blob create
> to indicate the blob create ioctl is used for create a userptr
> blob resource.
> 
> Signed-off-by: Honglei Huang <Honglei1.Huang@....com>
> ---
>   include/uapi/linux/virtio_gpu.h | 2 ++
>   1 file changed, 2 insertions(+)
> 
> diff --git a/include/uapi/linux/virtio_gpu.h b/include/uapi/linux/virtio_gpu.h
> index b9a9783f0b14..0a6b56acbc13 100644
> --- a/include/uapi/linux/virtio_gpu.h
> +++ b/include/uapi/linux/virtio_gpu.h
> @@ -323,6 +323,7 @@ struct virtio_gpu_cmd_submit {
>   
>   #define VIRTIO_GPU_CAPSET_VIRGL 1
>   #define VIRTIO_GPU_CAPSET_VIRGL2 2
> +#define VIRTIO_GPU_CAPSET_HSAKMT 7

The changes to add VIRTIO_GPU_CAPSET_VENUS and VIRTIO_GPU_CAPSET_DRM are 
already merged so this should be rebased for clean apply.

Number 7 is also occupied since 2023:
https://chromium.googlesource.com/crosvm/crosvm/+/e4c1878733937042111fca58899a3a94002bfef0%5E%21/rutabaga_gfx/src/rutabaga_utils.rs

VCL, a proposed VirtIO-GPU OpenCL driver, is also going to use that number:
https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/31634/diffs?commit_id=55a1a8a32057e83819b046f2de03aca333b052b4

I think you should talk with Antonio Caggiano, who picked the number for 
VCL, to allocate a number without a conflict with VCL.

Gurchetan (the author of Rutabaga change allocating the number), I think 
you should notify the number usage by sending a patch for Linux or 
virtio-spec.

Regards,
Akihiko Odaki

>   
>   /* VIRTIO_GPU_CMD_GET_CAPSET_INFO */
>   struct virtio_gpu_get_capset_info {
> @@ -415,6 +416,7 @@ struct virtio_gpu_resource_create_blob {
>   #define VIRTIO_GPU_BLOB_FLAG_USE_MAPPABLE     0x0001
>   #define VIRTIO_GPU_BLOB_FLAG_USE_SHAREABLE    0x0002
>   #define VIRTIO_GPU_BLOB_FLAG_USE_CROSS_DEVICE 0x0004
> +#define VIRTIO_GPU_BLOB_FLAG_USE_USERPTR      0x0008
>   	/* zero is invalid blob mem */
>   	__le32 blob_mem;
>   	__le32 blob_flags;