Re: [PATCH] drm/prime: Unbreak virtgpu dma-buf export

From: Dominik Behr <dbehr@chromium.org>
To: Rob Clark <robdclark@gmail.com>
Cc: dri-devel@lists.freedesktop.org,
	"Rob Clark" <robdclark@chromium.org>,
	"Dominik Behr" <dbehr@chromium.org>,
	"Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
	"Maxime Ripard" <mripard@kernel.org>,
	"Thomas Zimmermann" <tzimmermann@suse.de>,
	"David Airlie" <airlied@gmail.com>,
	"Daniel Vetter" <daniel@ffwll.ch>,
	"Sumit Semwal" <sumit.semwal@linaro.org>,
	"Christian König" <christian.koenig@amd.com>,
	"Simon Ser" <contact@emersion.fr>,
	"open list" <linux-kernel@vger.kernel.org>,
	"open list:DMA BUFFER SHARING
	FRAMEWORK:Keyword:bdma_(?:buf|fence|resv)b"
	<linux-media@vger.kernel.org>,
	"moderated list:DMA BUFFER SHARING
	FRAMEWORK:Keyword:bdma_(?:buf|fence|resv)b"
	<linaro-mm-sig@lists.linaro.org>
Subject: Re: [PATCH] drm/prime: Unbreak virtgpu dma-buf export
Date: Mon, 25 Mar 2024 15:38:06 -0700	[thread overview]
Message-ID: <CABUrSUBTz7n6Yg_4wvGR+W__AKn5Vj4aWuLg5p3bDWye-PwExg@mail.gmail.com> (raw)
In-Reply-To: <20240322214801.319975-1-robdclark@gmail.com>

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
>