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drm/amdgpu: place VRAM-capable dma-buf imports in the PREEMPT domain

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An imported dma-buf BO backed by a VRAM-capable exporter holds no host
pages of its own, yet when validated into TTM_PL_TT it is charged against
the GTT page budget; importing many such buffers can exhaust that budget
and fail with -ENOMEM even though no host memory is used. Set
AMDGPU_GEM_CREATE_PREEMPTIBLE on these imports so they land in the PREEMPT
domain instead, which is GTT-like and still bound (keeping the exporter
resident) but carries no host-page limit.

Signed-off-by: Mukul Joshi <mukul.joshi@amd.com>
Reviewed-by: Felix Kuehling <felix.kuehling@amd.com>
Reviewed-by: Alex Deucher <alexander.deucher@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
This commit is contained in:
Mukul Joshi 2026-09-18 14:06:07 -04:00 committed by Alex Deucher
parent 222627765a
commit 78cdd96ab4
1 changed files with 20 additions and 0 deletions
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20
drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
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@ -472,6 +472,15 @@ amdgpu_dma_buf_create_obj(struct drm_device *dev, struct dma_buf *dma_buf)
AMDGPU_GEM_CREATE_COHERENT |
AMDGPU_GEM_CREATE_EXT_COHERENT |
AMDGPU_GEM_CREATE_UNCACHED);
/*
* A VRAM-capable import is backed by the exporter's device
* memory, not host pages of its own. Place it in the PREEMPT
* domain (GTT-like, but with no host-page budget) so many such
* imports cannot exhaust the GTT limit.
*/
if (other->preferred_domains & AMDGPU_GEM_DOMAIN_VRAM)
flags |= AMDGPU_GEM_CREATE_PREEMPTIBLE;
}
ret = amdgpu_gem_object_create(adev, dma_buf->size, PAGE_SIZE,
@ -618,6 +627,17 @@ struct drm_gem_object *amdgpu_gem_prime_import(struct drm_device *dev,
return ERR_CAST(attach);
}
/*
* The PREEMPT domain is only correct when the attachment actually
* resolves to P2P access, in which case the import lives in the
* exporter's VRAM and consumes no host GTT pages. Without P2P the
* import is staged in system memory and must count against the GTT
* budget normally, so drop AMDGPU_GEM_CREATE_PREEMPTIBLE again. The
* BO is not published yet, so clearing the flag here is race-free.
*/
if (!attach->peer2peer)
gem_to_amdgpu_bo(obj)->flags &= ~AMDGPU_GEM_CREATE_PREEMPTIBLE;
get_dma_buf(dma_buf);
obj->import_attach = attach;
return obj;