Re: [PATCH] drm/amdgpu: Pin buffer while vmap'ing exported dma-buf objects

[Thomas Zimmermann]

Hi

Am 18.08.25 um 14:40 schrieb Christian König:
[...]
> > +static int amdgpu_dma_buf_vmap(struct dma_buf *dma_buf, struct iosys_map *map)
> > +{
> > +	struct drm_gem_object *obj = dma_buf->priv;
> > +	struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
> > +	int ret;
> > +
> > +	/*
> > +	 * Pin to keep buffer in place while it's vmap'ed. The actual
> > +	 * location is not important as long as it's mapable.
> Yeah, exactly that won't work here. Most of the locations are not CPU accessible.
>
> You could use AMDGPU_GEM_DOMAIN_GTT, that should most likely work in all cases but isn't necessarily the most optimal solution.

No problem about that, but why not a bit more flexibility? When udl 
copies from the buffer, it is likely pinned to VRAM.

A bit mask of _CPU, _GTT, and _VRAM should work fine. The other domains 
are probably irrelevant for our use case.

Best regards
Thomas

> Regards,
> Christian.
>
> > +	 *
> > +	 * This code is required for exporting to GEM-SHMEM without S/G table.
> > +	 * Once GEM-SHMEM supports dynamic imports, it should be dropped.
> > +	 */
> > +	ret = amdgpu_bo_pin(bo, AMDGPU_GEM_DOMAIN_MASK);
> > +	if (ret)
> > +		return ret;
> > +	ret = drm_gem_dmabuf_vmap(dma_buf, map);
> > +	if (ret)
> > +		amdgpu_bo_unpin(bo);
> > +
> > +	return ret;
> > +}
> > +
> > +static void amdgpu_dma_buf_vunmap(struct dma_buf *dma_buf, struct iosys_map *map)
> > +{
> > +	struct drm_gem_object *obj = dma_buf->priv;
> > +	struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
> > +
> > +	drm_gem_dmabuf_vunmap(dma_buf, map);
> > +	amdgpu_bo_unpin(bo);
> > +}
> > +
> >   const struct dma_buf_ops amdgpu_dmabuf_ops = {
> >   	.attach = amdgpu_dma_buf_attach,
> >   	.pin = amdgpu_dma_buf_pin,
> > @@ -294,8 +326,8 @@ const struct dma_buf_ops amdgpu_dmabuf_ops = {
> >   	.release = drm_gem_dmabuf_release,
> >   	.begin_cpu_access = amdgpu_dma_buf_begin_cpu_access,
> >   	.mmap = drm_gem_dmabuf_mmap,
> > -	.vmap = drm_gem_dmabuf_vmap,
> > -	.vunmap = drm_gem_dmabuf_vunmap,
> > +	.vmap = amdgpu_dma_buf_vmap,
> > +	.vunmap = amdgpu_dma_buf_vunmap,
> >   };
> >   
> >   /**

--
--
Thomas Zimmermann
Graphics Driver Developer
SUSE Software Solutions Germany GmbH
Frankenstrasse 146, 90461 Nuernberg, Germany
GF: Ivo Totev, Andrew Myers, Andrew McDonald, Boudien Moerman
HRB 36809 (AG Nuernberg)