github-mirror/linux
1
0
Fork 0
mirror of https://github.com/torvalds/linux.git synced 2026-09-24 06:24:02 +02:00
Code Issues Actions Packages Projects Releases Wiki Activity Graph

drm/amdgpu: hold a runtime PM reference for P2P dma-buf attachments

Browse Source 
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 030631e97b ("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: 030631e97b ("drm/amdgpu: revert "take runtime pm reference when we attach a buffer" v2")
Suggested-by: Christian König <christian.koenig@amd.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Signed-off-by: Mike Lothian <mike@fireburn.co.uk>
Assisted-by: Claude:Opus-5 [Claude Code]
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
(cherry picked from commit 062ff15e30a48d14fb7d7558eba84f8dc97197f0)
Cc: stable@vger.kernel.org
This commit is contained in:
Mike Lothian 2026-09-12 00:29:08 +01:00 committed by Alex Deucher
parent 5f28bb1c2c
commit 636139603b
1 changed files with 42 additions and 1 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

43
drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
View File

@ -43,6 +43,7 @@
#include <linux/dma-buf.h>
#include <linux/dma-fence-array.h>
#include <linux/pci-p2pdma.h>
#include <linux/pm_runtime.h>
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,