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>
---
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/vmwgfx/vmwgfx_ttm_buffer.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
index bf0bc46..a5fd128 100644
--- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
+++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c
@@ -362,7 +362,7 @@ static void vmw_ttm_unmap_from_dma(struct vmw_ttm_tt *vmw_tt)
{
struct device *dev = vmw_tt->dev_priv->dev->dev;
- dma_unmap_sg(dev, vmw_tt->sgt.sgl, vmw_tt->sgt.nents,
+ dma_unmap_sg(dev, vmw_tt->sgt.sgl, vmw_tt->sgt.orig_nents,
DMA_BIDIRECTIONAL);
vmw_tt->sgt.nents = vmw_tt->sgt.orig_nents;
}
@@ -449,10 +449,10 @@ static int vmw_ttm_map_dma(struct vmw_ttm_tt *vmw_tt)
if (unlikely(ret != 0))
goto out_sg_alloc_fail;
- if (vsgt->num_pages > vmw_tt->sgt.nents) {
+ if (vsgt->num_pages > vmw_tt->sgt.orig_nents) {
uint64_t over_alloc =
sgl_size * (vsgt->num_pages -
- vmw_tt->sgt.nents);
+ vmw_tt->sgt.orig_nents);
ttm_mem_global_free(glob, over_alloc);
vmw_tt->sg_alloc_size -= over_alloc;
--
1.9.1
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