[PATCH v2] drm/virtio: use virtio_max_dma_size

[Gerd Hoffmann]

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 <ler...@redhat.com>
Signed-off-by: Gerd Hoffmann <kra...@redhat.com>
---
 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..6e44568813dd 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
        };
+       unsigned 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 &= ~(size_t)(PAGE_SIZE - 1);
+       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