From 636139603b99d2e3a18a46cf3f8d39313ce8042e Mon Sep 17 00:00:00 2001 From: Mike Lothian Date: Sat, 12 Sep 2026 00:29:08 +0100 Subject: [PATCH] drm/amdgpu: hold a runtime PM reference for P2P dma-buf attachments MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit amdgpu_dma_buf_map() adds VRAM to the allowed domains for a peer2peer attachment. GTT is only a fallback placement when VRAM is preferred, so ttm_bo_validate() migrates the buffer from GTT into VRAM. While the exporting device is runtime suspended its SDMA rings are down and the move fails: amdgpu: Move buffer fallback to memcpy unavailable An importer on a second GPU reaches this holding no runtime PM reference on the exporter, e.g. a compositor on the APU submitting a frame that references a buffer exported by an idle dGPU: amdgpu_cs_ioctl -> amdgpu_cs_parser_bos -> amdgpu_cs_bo_validate -> ttm_bo_validate -> amdgpu_bo_move -> dma_buf_map_attachment -> amdgpu_dma_buf_map -> ttm_bo_validate -> amdgpu_bo_move Pinning a dma-buf into VRAM has the same requirement, which commit 030631e97b20 ("drm/amdgpu: revert "take runtime pm reference when we attach a buffer" v2") called out as the one case that would need the reference back. Take it in attach and drop it in detach. pm_runtime_get_if_active() never resumes the device, so it cannot deadlock against the reservation taken during resume, which is why the old pm_runtime_get_sync() had to go. If the device is not active, clear peer2peer instead: the buffer then stays in GTT, which remains accessible while the GPU is powered down. If runtime PM is disabled, take a plain reference so the put in detach stays balanced. Fixes: 030631e97b20 ("drm/amdgpu: revert "take runtime pm reference when we attach a buffer" v2") Suggested-by: Christian König Reviewed-by: Christian König Signed-off-by: Mike Lothian Assisted-by: Claude:Opus-5 [Claude Code] Signed-off-by: Alex Deucher (cherry picked from commit 062ff15e30a48d14fb7d7558eba84f8dc97197f0) Cc: stable@vger.kernel.org --- drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 43 ++++++++++++++++++++- 1 file changed, 42 insertions(+), 1 deletion(-) diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c index b33c300e26e2..9adf3eed8822 100644 --- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c +++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c @@ -43,6 +43,7 @@ #include #include #include +#include static const struct dma_buf_attach_ops amdgpu_dma_buf_attach_ops; @@ -100,15 +101,54 @@ static int amdgpu_dma_buf_attach(struct dma_buf *dmabuf, pci_p2pdma_distance(adev->pdev, attach->dev, false) < 0) attach->peer2peer = false; + /* + * Only allow P2P while the exporter is active, and keep it active + * until detach. With runtime PM disabled take a plain reference so + * the put in detach stays balanced. + */ + if (attach->peer2peer) { + struct device *dev = adev_to_drm(adev)->dev; + int ret = pm_runtime_get_if_active(dev); + + if (!ret) + attach->peer2peer = false; + else if (ret < 0) + pm_runtime_get_noresume(dev); + } + r = dma_resv_lock(bo->tbo.base.resv, NULL); if (r) - return r; + goto err_pm_put; amdgpu_vm_bo_update_shared(bo); dma_resv_unlock(bo->tbo.base.resv); return 0; + +err_pm_put: + if (attach->peer2peer) + pm_runtime_put_autosuspend(adev_to_drm(adev)->dev); + return r; +} + +/** + * amdgpu_dma_buf_detach - &dma_buf_ops.detach implementation + * + * @dmabuf: DMA-buf where we remove the attachment from + * @attach: the attachment to remove + * + * Drop the runtime PM reference taken in amdgpu_dma_buf_attach(). + */ +static void amdgpu_dma_buf_detach(struct dma_buf *dmabuf, + struct dma_buf_attachment *attach) +{ + struct drm_gem_object *obj = dmabuf->priv; + struct amdgpu_bo *bo = gem_to_amdgpu_bo(obj); + struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev); + + if (attach->peer2peer) + pm_runtime_put_autosuspend(adev_to_drm(adev)->dev); } /** @@ -350,6 +390,7 @@ static void amdgpu_dma_buf_vunmap(struct dma_buf *dma_buf, struct iosys_map *map const struct dma_buf_ops amdgpu_dmabuf_ops = { .attach = amdgpu_dma_buf_attach, + .detach = amdgpu_dma_buf_detach, .pin = amdgpu_dma_buf_pin, .unpin = amdgpu_dma_buf_unpin, .map_dma_buf = amdgpu_dma_buf_map,