Am 10.01.24 um 11:22 schrieb Daniel Vetter:
On Wed, Jan 10, 2024 at 11:19:37AM +0100, Christian König wrote:
Am 10.01.24 um 10:56 schrieb Julia Zhang:
drm_gem_map_attach() requires drm_gem_object_funcs.get_sg_table to be
implemented, or else return ENOSYS. Virtio has no get_sg_table
implemented for vram object. To fix this, add a new device_attach to
call drm_gem_map_attach() for shmem object and return 0 for vram object
instead of calling drm_gem_map_attach for both of these two kinds of
object.
Well as far as I can see this is nonsense from the DMA-buf side of things.
SG tables are always needed as long as you don't re-import the same object
into your driver and then you shouldn't end up in this function in the first
place.
So that drm_gem_map_attach() requires get_sg_table to be implemented is
intentional and should never be overridden like this.
See my reply, tldr; you're allowed to reject ->attach with -EBUSY to
handle exactly this case of non-shareable buffer types. But definitely
don't silently fail, that's a "we'll oops on map_attachment" kind of bug
:-)
Ah, yes that makes much more sense!
So basically just the "return 0;" needs to be "return -EBUSY;".
Regards,
Christian.
-Sima
Regards,
Christian.
Signed-off-by: Julia Zhang <julia.zhang@xxxxxxx>
---
drivers/gpu/drm/virtio/virtgpu_prime.c | 14 +++++++++++++-
1 file changed, 13 insertions(+), 1 deletion(-)
diff --git a/drivers/gpu/drm/virtio/virtgpu_prime.c b/drivers/gpu/drm/virtio/virtgpu_prime.c
index 44425f20d91a..f0b0ff6f3813 100644
--- a/drivers/gpu/drm/virtio/virtgpu_prime.c
+++ b/drivers/gpu/drm/virtio/virtgpu_prime.c
@@ -71,6 +71,18 @@ static void virtgpu_gem_unmap_dma_buf(struct dma_buf_attachment *attach,
drm_gem_unmap_dma_buf(attach, sgt, dir);
}
+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);
+
+ if (virtio_gpu_is_vram(bo))
+ return 0;
+
+ return drm_gem_map_attach(dma_buf, attach);
+}
+
static const struct virtio_dma_buf_ops virtgpu_dmabuf_ops = {
.ops = {
.cache_sgt_mapping = true,
@@ -83,7 +95,7 @@ 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,
};
