2019-08-21 11:24:10

by Gerd Hoffmann

Subject: [PATCH v5] drm/virtio: use virtio_max_dma_size

We must make sure our scatterlist segments are not too big, otherwise
we might see swiotlb failures (happens with sev, also reproducable with
swiotlb=force).

Suggested-by: Laszlo Ersek <[email protected]>
Signed-off-by: Gerd Hoffmann <[email protected]>
---
drivers/gpu/drm/virtio/virtgpu_object.c | 10 ++++++++--
1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
index b2da31310d24..09b526518f5a 100644
--- a/drivers/gpu/drm/virtio/virtgpu_object.c
+++ b/drivers/gpu/drm/virtio/virtgpu_object.c
@@ -204,6 +204,7 @@ int virtio_gpu_object_get_sg_table(struct virtio_gpu_device *qdev,
.interruptible = false,
.no_wait_gpu = false
};
+ size_t max_segment;

/* wtf swapping */
if (bo->pages)
@@ -215,8 +216,13 @@ int virtio_gpu_object_get_sg_table(struct virtio_gpu_device *qdev,
if (!bo->pages)
goto out;

- ret = sg_alloc_table_from_pages(bo->pages, pages, nr_pages, 0,
- nr_pages << PAGE_SHIFT, GFP_KERNEL);
+ max_segment = virtio_max_dma_size(qdev->vdev);
+ max_segment &= PAGE_MASK;
+ if (max_segment > SCATTERLIST_MAX_SEGMENT)
+ max_segment = SCATTERLIST_MAX_SEGMENT;
+ ret = __sg_alloc_table_from_pages(bo->pages, pages, nr_pages, 0,
+ nr_pages << PAGE_SHIFT,
+ max_segment, GFP_KERNEL);
if (ret)
goto out;
return 0;
--
2.18.1

2019-08-22 14:26:55

by Laszlo Ersek

Subject: Re: [PATCH v5] drm/virtio: use virtio_max_dma_size

On 08/21/19 13:12, Gerd Hoffmann wrote:
> We must make sure our scatterlist segments are not too big, otherwise
> we might see swiotlb failures (happens with sev, also reproducable with
> swiotlb=force).
>
> Suggested-by: Laszlo Ersek <[email protected]>
> Signed-off-by: Gerd Hoffmann <[email protected]>
> ---
> drivers/gpu/drm/virtio/virtgpu_object.c | 10 ++++++++--
> 1 file changed, 8 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/virtio/virtgpu_object.c b/drivers/gpu/drm/virtio/virtgpu_object.c
> index b2da31310d24..09b526518f5a 100644
> --- a/drivers/gpu/drm/virtio/virtgpu_object.c
> +++ b/drivers/gpu/drm/virtio/virtgpu_object.c
> @@ -204,6 +204,7 @@ int virtio_gpu_object_get_sg_table(struct virtio_gpu_device *qdev,
> .interruptible = false,
> .no_wait_gpu = false
> };
> + size_t max_segment;
>
> /* wtf swapping */
> if (bo->pages)
> @@ -215,8 +216,13 @@ int virtio_gpu_object_get_sg_table(struct virtio_gpu_device *qdev,
> if (!bo->pages)
> goto out;
>
> - ret = sg_alloc_table_from_pages(bo->pages, pages, nr_pages, 0,
> - nr_pages << PAGE_SHIFT, GFP_KERNEL);
> + max_segment = virtio_max_dma_size(qdev->vdev);
> + max_segment &= PAGE_MASK;
> + if (max_segment > SCATTERLIST_MAX_SEGMENT)
> + max_segment = SCATTERLIST_MAX_SEGMENT;
> + ret = __sg_alloc_table_from_pages(bo->pages, pages, nr_pages, 0,
> + nr_pages << PAGE_SHIFT,
> + max_segment, GFP_KERNEL);
> if (ret)
> goto out;
> return 0;
>

Reviewed-by: Laszlo Ersek <[email protected]>

Thanks!
Laszlo