linux-kernel - Re: [PATCH AUTOSEL 6.12 11/30] drm/amdgpu: allow pinning DMA-bufs into VRAM if all importers can do P2P

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Message-ID: <CADnq5_PqqY07uBERuSGC--+=dsffxydrPrvzt7pw6SfmmqbDjw@mail.gmail.com>
Date: Mon, 14 Apr 2025 09:31:01 -0400
From: Alex Deucher <alexdeucher@...il.com>
To: Sasha Levin <sashal@...nel.org>
Cc: linux-kernel@...r.kernel.org, stable@...r.kernel.org, 
	Christian König <christian.koenig@....com>, 
	Simona Vetter <simona.vetter@...ll.ch>, Felix Kuehling <felix.kuehling@....com>, 
	Pak Nin Lui <pak.lui@....com>, Alex Deucher <alexander.deucher@....com>, airlied@...il.com, 
	simona@...ll.ch, sumit.semwal@...aro.org, Yunxiang.Li@....com, 
	matthew.auld@...el.com, tvrtko.ursulin@...lia.com, 
	amd-gfx@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org, 
	linux-media@...r.kernel.org, linaro-mm-sig@...ts.linaro.org
Subject: Re: [PATCH AUTOSEL 6.12 11/30] drm/amdgpu: allow pinning DMA-bufs
 into VRAM if all importers can do P2P

On Mon, Apr 14, 2025 at 9:29 AM Sasha Levin <sashal@...nel.org> wrote:
>
> From: Christian König <christian.koenig@....com>
>
> [ Upstream commit f5e7fabd1f5c65b2e077efcdb118cfa67eae7311 ]
>
> Try pinning into VRAM to allow P2P with RDMA NICs without ODP
> support if all attachments can do P2P. If any attachment can't do
> P2P just pin into GTT instead.
>
> Acked-by: Simona Vetter <simona.vetter@...ll.ch>
> Signed-off-by: Christian König <christian.koenig@....com>
> Signed-off-by: Felix Kuehling <felix.kuehling@....com>
> Reviewed-by: Felix Kuehling <felix.kuehling@....com>
> Tested-by: Pak Nin Lui <pak.lui@....com>
> Cc: Simona Vetter <simona.vetter@...ll.ch>
> Signed-off-by: Alex Deucher <alexander.deucher@....com>
> Signed-off-by: Sasha Levin <sashal@...nel.org>

This should not go to stable.  It depends on dmem groups.


Alex

> ---
>  drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 25 +++++++++++++++------
>  1 file changed, 18 insertions(+), 7 deletions(-)
>
> diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> index 8e81a83d37d84..83390143c2e9f 100644
> --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
> @@ -72,11 +72,25 @@ static int amdgpu_dma_buf_attach(struct dma_buf *dmabuf,
>   */
>  static int amdgpu_dma_buf_pin(struct dma_buf_attachment *attach)
>  {
> -       struct drm_gem_object *obj = attach->dmabuf->priv;
> -       struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj);
> +       struct dma_buf *dmabuf = attach->dmabuf;
> +       struct amdgpu_bo *bo = gem_to_amdgpu_bo(dmabuf->priv);
> +       u32 domains = bo->preferred_domains;
>
> -       /* pin buffer into GTT */
> -       return amdgpu_bo_pin(bo, AMDGPU_GEM_DOMAIN_GTT);
> +       dma_resv_assert_held(dmabuf->resv);
> +
> +       /*
> +        * Try pinning into VRAM to allow P2P with RDMA NICs without ODP
> +        * support if all attachments can do P2P. If any attachment can't do
> +        * P2P just pin into GTT instead.
> +        */
> +       list_for_each_entry(attach, &dmabuf->attachments, node)
> +               if (!attach->peer2peer)
> +                       domains &= ~AMDGPU_GEM_DOMAIN_VRAM;
> +
> +       if (domains & AMDGPU_GEM_DOMAIN_VRAM)
> +               bo->flags |= AMDGPU_GEM_CREATE_CPU_ACCESS_REQUIRED;
> +
> +       return amdgpu_bo_pin(bo, domains);
>  }
>
>  /**
> @@ -131,9 +145,6 @@ static struct sg_table *amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
>                 r = ttm_bo_validate(&bo->tbo, &bo->placement, &ctx);
>                 if (r)
>                         return ERR_PTR(r);
> -
> -       } else if (bo->tbo.resource->mem_type != TTM_PL_TT) {
> -               return ERR_PTR(-EBUSY);
>         }
>
>         switch (bo->tbo.resource->mem_type) {
> --
> 2.39.5
>