The Documentation/DMA-API-HOWTO.txt states that dma_map_sg returns the
numer of the created entries in the DMA address space. However the
subsequent calls to dma_sync_sg_for_{device,cpu} and dma_unmap_sg must be
called with the original number of entries passed to dma_map_sg. The
sg_table->nents in turn holds the result of the dma_map_sg call as stated
in include/linux/scatterlist.h. Adapt the code to obey those rules.
Signed-off-by: Marek Szyprowski <m.szyprowski@xxxxxxxxxxx>
Reviewed-by: Christian König <christian.koenig@xxxxxxx>
---
For more information, see '[PATCH v2 00/21] DRM: fix struct sg_table nents
vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/4/373
---
drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c | 7 ++++---
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c | 8 ++++----
2 files changed, 8 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 43d8ed7..4df813e 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
@@ -307,8 +307,9 @@ static struct sg_table *amdgpu_dma_buf_map(struct dma_buf_attachment *attach,
if (IS_ERR(sgt))
return sgt;
- if (!dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->nents, dir,
- DMA_ATTR_SKIP_CPU_SYNC))
+ sgt->nents = dma_map_sg_attrs(attach->dev, sgt->sgl, sgt->orig_nents,
+ dir, DMA_ATTR_SKIP_CPU_SYNC);
+ if (!sgt->nents)
goto error_free;
break;
@@ -349,7 +350,7 @@ static void amdgpu_dma_buf_unmap(struct dma_buf_attachment *attach,
struct amdgpu_device *adev = amdgpu_ttm_adev(bo->tbo.bdev);
if (sgt->sgl->page_link) {
- dma_unmap_sg(attach->dev, sgt->sgl, sgt->nents, dir);
+ dma_unmap_sg(attach->dev, sgt->sgl, sgt->orig_nents, dir);
sg_free_table(sgt);
kfree(sgt);
} else {
diff --git a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
index eff1f73..1f8c507 100644
--- a/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
+++ b/drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
@@ -1043,7 +1043,6 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_tt *ttm)
{
struct amdgpu_device *adev = amdgpu_ttm_adev(ttm->bdev);
struct amdgpu_ttm_tt *gtt = (void *)ttm;
- unsigned nents;
int r;
int write = !(gtt->userflags & AMDGPU_GEM_USERPTR_READONLY);
@@ -1059,8 +1058,9 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_tt *ttm)
/* Map SG to device */
r = -ENOMEM;
- nents = dma_map_sg(adev->dev, ttm->sg->sgl, ttm->sg->nents, direction);
- if (nents == 0)
+ ttm->sg->nents = dma_map_sg(adev->dev, ttm->sg->sgl,
+ ttm->sg->orig_nents, direction);
+ if (ttm->sg->nents == 0)
goto release_sg;
/* convert SG to linear array of pages and dma addresses */
@@ -1091,7 +1091,7 @@ static void amdgpu_ttm_tt_unpin_userptr(struct ttm_tt *ttm)
return;
/* unmap the pages mapped to the device */
- dma_unmap_sg(adev->dev, ttm->sg->sgl, ttm->sg->nents, direction);
+ dma_unmap_sg(adev->dev, ttm->sg->sgl, ttm->sg->orig_nents, direction);
sg_free_table(ttm->sg);
--
1.9.1
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