From: Rob Clark <robdclark@chromium.org>

virtgpu "vram" GEM objects do not implement obj->get_sg_table().  But
they also don't use drm_gem_map_dma_buf().  In fact they may not even
have guest visible pages.  But it is perfectly fine to export and share
with other virtual devices.

Reported-by: Dominik Behr <dbehr@chromium.org>
Fixes: 207395da5a97 ("drm/prime: reject DMA-BUF attach when get_sg_table is missing")
Signed-off-by: Rob Clark <robdclark@chromium.org>
---
 drivers/gpu/drm/drm_prime.c | 7 ++++++-
 1 file changed, 6 insertions(+), 1 deletion(-)

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 7352bde299d5..64dd6276e828 100644
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -582,7 +582,12 @@ int drm_gem_map_attach(struct dma_buf *dma_buf,
 {
 	struct drm_gem_object *obj = dma_buf->priv;
 
-	if (!obj->funcs->get_sg_table)
+	/*
+	 * drm_gem_map_dma_buf() requires obj->get_sg_table(), but drivers
+	 * that implement their own ->map_dma_buf() do not.
+	 */
+	if ((dma_buf->ops->map_dma_buf == drm_gem_map_dma_buf) &&
+	    !obj->funcs->get_sg_table)
 		return -ENOSYS;
 
 	return drm_gem_pin(obj);
-- 
2.44.0

Makes sense to me!

Reviewed-by: Simon Ser <contact@emersion.fr>

On Tue, Mar 26, 2024 at 2:15 AM Simon Ser <contact@emersion.fr> wrote:
>
> Makes sense to me!
>
> Reviewed-by: Simon Ser <contact@emersion.fr>

Thanks.. any chance I could talk you into pushing to drm-misc-fixes?

BR,
-R

On Thursday, March 28th, 2024 at 19:47, Rob Clark <robdclark@gmail.com> wrote:

> any chance I could talk you into pushing to drm-misc-fixes?

Oh sorry, I thought you had access… Pushed with a minor edit to remove
unnecessary parentheses to make checkpatch happy!

On Thu, Mar 28, 2024 at 11:54 AM Simon Ser <contact@emersion.fr> wrote:
>
> On Thursday, March 28th, 2024 at 19:47, Rob Clark <robdclark@gmail.com> wrote:
>
> > any chance I could talk you into pushing to drm-misc-fixes?
>
> Oh sorry, I thought you had access… Pushed with a minor edit to remove
> unnecessary parentheses to make checkpatch happy!

Thanks!

BR,
-R

It also fixes importing virtgpu blobs into real hardware, for instance
amdgpu for DRI_PRIME rendering.


On Fri, Mar 22, 2024 at 2:48 PM Rob Clark <robdclark@gmail.com> wrote:
>
> From: Rob Clark <robdclark@chromium.org>
>
> virtgpu "vram" GEM objects do not implement obj->get_sg_table().  But
> they also don't use drm_gem_map_dma_buf().  In fact they may not even
> have guest visible pages.  But it is perfectly fine to export and share
> with other virtual devices.
>
> Reported-by: Dominik Behr <dbehr@chromium.org>
> Fixes: 207395da5a97 ("drm/prime: reject DMA-BUF attach when get_sg_table is missing")
> Signed-off-by: Rob Clark <robdclark@chromium.org>
> ---
>  drivers/gpu/drm/drm_prime.c | 7 ++++++-
>  1 file changed, 6 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
> index 7352bde299d5..64dd6276e828 100644
> --- a/drivers/gpu/drm/drm_prime.c
> +++ b/drivers/gpu/drm/drm_prime.c
> @@ -582,7 +582,12 @@ int drm_gem_map_attach(struct dma_buf *dma_buf,
>  {
>         struct drm_gem_object *obj = dma_buf->priv;
>
> -       if (!obj->funcs->get_sg_table)
> +       /*
> +        * drm_gem_map_dma_buf() requires obj->get_sg_table(), but drivers
> +        * that implement their own ->map_dma_buf() do not.
> +        */
> +       if ((dma_buf->ops->map_dma_buf == drm_gem_map_dma_buf) &&
> +           !obj->funcs->get_sg_table)
>                 return -ENOSYS;
>
>         return drm_gem_pin(obj);
> --
> 2.44.0
>