linux-kernel - Re: [PATCH v2 1/1] drm/virtio: Implement device

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Message-ID: <cab2246a-5ed8-4651-999f-260c1c4275ad@amd.com>
Date: Mon, 29 Jan 2024 14:12:19 +0100
From: Christian König <christian.koenig@....com>
To: Julia Zhang <julia.zhang@....com>,
 Gurchetan Singh <gurchetansingh@...omium.org>, Chia-I Wu
 <olvaffe@...il.com>, David Airlie <airlied@...hat.com>,
 Gerd Hoffmann <kraxel@...hat.com>, linux-kernel@...r.kernel.org,
 dri-devel@...ts.freedesktop.org, amd-gfx@...ts.freedesktop.org,
 virtualization@...ts.linux-foundation.org
Cc: Alex Deucher <alexander.deucher@....com>, Daniel Vetter
 <daniel@...ll.ch>, David Airlie <airlied@...il.com>,
 Erik Faye-Lund <kusmabite@...il.com>, Marek Olšák
 <marek.olsak@....com>,
 Pierre-Eric Pelloux-Prayer <pierre-eric.pelloux-prayer@....com>,
 Honglei Huang <honglei1.huang@....com>, Chen Jiqian <Jiqian.Chen@....com>,
 Huang Rui <ray.huang@....com>
Subject: Re: [PATCH v2 1/1] drm/virtio: Implement device_attach

Am 29.01.24 um 11:31 schrieb Julia Zhang:
> As vram objects don't have backing pages and thus can't implement
> drm_gem_object_funcs.get_sg_table callback. This removes drm dma-buf
> callbacks in virtgpu_gem_map_dma_buf()/virtgpu_gem_unmap_dma_buf()
> and implement virtgpu specific map/unmap/attach callbacks to support
> both of shmem objects and vram objects.
>
> Signed-off-by: Julia Zhang <julia.zhang@....com>

I need to find more time to look into the code, but of hand I would say 
that this is the correct solution.

Regards,
Christian.

> ---
>   drivers/gpu/drm/virtio/virtgpu_prime.c | 40 +++++++++++++++++++++++---
>   1 file changed, 36 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_prime.c b/drivers/gpu/drm/virtio/virtgpu_prime.c
> index 44425f20d91a..b490a5343b06 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_prime.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_prime.c
> @@ -49,11 +49,26 @@ virtgpu_gem_map_dma_buf(struct dma_buf_attachment *attach,
>   {
>   	struct drm_gem_object *obj = attach->dmabuf->priv;
>   	struct virtio_gpu_object *bo = gem_to_virtio_gpu_obj(obj);
> +	struct sg_table *sgt;
> +	int ret;
>   
>   	if (virtio_gpu_is_vram(bo))
>   		return virtio_gpu_vram_map_dma_buf(bo, attach->dev, dir);
>   
> -	return drm_gem_map_dma_buf(attach, dir);
> +	sgt = drm_prime_pages_to_sg(obj->dev,
> +				    to_drm_gem_shmem_obj(obj)->pages,
> +				    obj->size >> PAGE_SHIFT);
> +	if (IS_ERR(sgt))
> +		return sgt;
> +
> +	ret = dma_map_sgtable(attach->dev, sgt, dir, DMA_ATTR_SKIP_CPU_SYNC);
> +	if (ret) {
> +		sg_free_table(sgt);
> +		kfree(sgt);
> +		return ERR_PTR(ret);
> +	}
> +
> +	return sgt;
>   }
>   
>   static void virtgpu_gem_unmap_dma_buf(struct dma_buf_attachment *attach,
> @@ -63,12 +78,29 @@ static void virtgpu_gem_unmap_dma_buf(struct dma_buf_attachment *attach,
>   	struct drm_gem_object *obj = attach->dmabuf->priv;
>   	struct virtio_gpu_object *bo = gem_to_virtio_gpu_obj(obj);
>   
> +	if (!sgt)
> +		return;
> +
>   	if (virtio_gpu_is_vram(bo)) {
>   		virtio_gpu_vram_unmap_dma_buf(attach->dev, sgt, dir);
> -		return;
> +	} else {
> +		dma_unmap_sgtable(attach->dev, sgt, dir, DMA_ATTR_SKIP_CPU_SYNC);
> +		sg_free_table(sgt);
> +		kfree(sgt);
>   	}
> +}
> +
> +static int virtgpu_gem_device_attach(struct dma_buf *dma_buf,
> +				     struct dma_buf_attachment *attach)
> +{
> +	struct drm_gem_object *obj = attach->dmabuf->priv;
> +	struct virtio_gpu_object *bo = gem_to_virtio_gpu_obj(obj);
> +	int ret = 0;
> +
> +	if (!virtio_gpu_is_vram(bo) && obj->funcs->pin)
> +		ret = obj->funcs->pin(obj);
>   
> -	drm_gem_unmap_dma_buf(attach, sgt, dir);
> +	return ret;
>   }
>   
>   static const struct virtio_dma_buf_ops virtgpu_dmabuf_ops =  {
> @@ -83,7 +115,7 @@ static const struct virtio_dma_buf_ops virtgpu_dmabuf_ops =  {
>   		.vmap = drm_gem_dmabuf_vmap,
>   		.vunmap = drm_gem_dmabuf_vunmap,
>   	},
> -	.device_attach = drm_gem_map_attach,
> +	.device_attach = virtgpu_gem_device_attach,
>   	.get_uuid = virtgpu_virtio_get_uuid,
>   };
>