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drm: amdgpu: fix common struct sg_table related issues 

The Documentation/DMA-API-HOWTO.txt states that the dma_map_sg() function
returns the number of the created entries in the DMA address space.
However the subsequent calls to the dma_sync_sg_for_{device,cpu}() and
dma_unmap_sg must be called with the original number of the entries
passed to the dma_map_sg().

struct sg_table is a common structure used for describing a non-contiguous
memory buffer, used commonly in the DRM and graphics subsystems. It
consists of a scatterlist with memory pages and DMA addresses (sgl entry),
as well as the number of scatterlist entries: CPU pages (orig_nents entry)
and DMA mapped pages (nents entry).

It turned out that it was a common mistake to misuse nents and orig_nents
entries, calling DMA-mapping functions with a wrong number of entries or
ignoring the number of mapped entries returned by the dma_map_sg()
function.

To avoid such issues, lets use a common dma-mapping wrappers operating
directly on the struct sg_table objects and use scatterlist page
iterators where possible. This, almost always, hides references to the
nents and orig_nents entries, making the code robust, easier to follow
and copy/paste safe.

Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com>
Reviewed-by: Christian König <christian.koenig@amd.com>
Link: https://patchwork.freedesktop.org/patch/371142/
Signed-off-by: Christian König <christian.koenig@amd.com>
This commit is contained in:
Marek Szyprowski 2020-06-19 12:36:04 +02:00 committed by Christian König
parent de48984486
commit 39913934e6
3 changed files with 10 additions and 13 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

6
drivers/gpu/drm/amd/amdgpu/amdgpu_dma_buf.c
View File

@ -307,8 +307,8 @@ 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))
if (dma_map_sgtable(attach->dev, sgt, dir,
DMA_ATTR_SKIP_CPU_SYNC))
goto error_free;
break;
@ -349,7 +349,7 @@ 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_sgtable(attach->dev, sgt, dir, 0);
sg_free_table(sgt);
kfree(sgt);
} else {

9
drivers/gpu/drm/amd/amdgpu/amdgpu_ttm.c
View File

@ -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);
@ -1058,9 +1057,8 @@ static int amdgpu_ttm_tt_pin_userptr(struct ttm_tt *ttm)
goto release_sg;
/* Map SG to device */
r = -ENOMEM;
nents = dma_map_sg(adev->dev, ttm->sg->sgl, ttm->sg->nents, direction);
if (nents == 0)
r = dma_map_sgtable(adev->dev, ttm->sg, direction, 0);
if (r)
goto release_sg;
/* convert SG to linear array of pages and dma addresses */
@ -1091,8 +1089,7 @@ 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_sgtable(adev->dev, ttm->sg, direction, 0);
sg_free_table(ttm->sg);
#if IS_ENABLED(CONFIG_DRM_AMDGPU_USERPTR)

8
drivers/gpu/drm/amd/amdgpu/amdgpu_vram_mgr.c
View File

@ -476,11 +476,11 @@ int amdgpu_vram_mgr_alloc_sgt(struct amdgpu_device *adev,
if (r)
goto error_free;
for_each_sg((*sgt)->sgl, sg, num_entries, i)
for_each_sgtable_sg((*sgt), sg, i)
sg->length = 0;
node = mem->mm_node;
for_each_sg((*sgt)->sgl, sg, num_entries, i) {
for_each_sgtable_sg((*sgt), sg, i) {
phys_addr_t phys = (node->start << PAGE_SHIFT) +
adev->gmc.aper_base;
size_t size = node->size << PAGE_SHIFT;
@ -500,7 +500,7 @@ int amdgpu_vram_mgr_alloc_sgt(struct amdgpu_device *adev,
return 0;
error_unmap:
for_each_sg((*sgt)->sgl, sg, num_entries, i) {
for_each_sgtable_sg((*sgt), sg, i) {
if (!sg->length)
continue;
@ -531,7 +531,7 @@ void amdgpu_vram_mgr_free_sgt(struct amdgpu_device *adev,
struct scatterlist *sg;
int i;
for_each_sg(sgt->sgl, sg, sgt->nents, i)
for_each_sgtable_sg(sgt, sg, i)
dma_unmap_resource(dev, sg->dma_address,
sg->length, dir,
DMA_ATTR_SKIP_CPU_SYNC);