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 <[email protected]> Reviewed-by: Felix Kuehling <[email protected]> --- v1->v2: - Check if p2p access is allowed. If not, clear the PREEMPT flag since the BO will be put in GTT domain. - v1 reviewed by Felix. drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 20 ++++++++++++++++++++ 1 file changed, 20 insertions(+) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c index 4031ebe075d8..bbe518757907 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c @@ -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; -- 2.55.0
