| Message ID | 20200505084614.30424-15-m.szyprowski@samsung.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | DRM: fix struct sg_table nents vs. orig_nents misuse | expand |
I'm not exactly an expert on this, but looks alright to me. Acked-by: Roland Scheidegger <sroland@vmware.com> Am 05.05.20 um 10:46 schrieb Marek Szyprowski: > 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 the 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. A common mistake was to ignore a result > of the dma_map_sg function and don't use the sg_table->orig_nents at all. > > To avoid such issues, lets use common dma-mapping wrappers operating > directly on the struct sg_table objects and adjust references to the > nents and orig_nents respectively. > > Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> > --- > For more information, see '[PATCH v3 00/25] DRM: fix struct sg_table nents > vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/5/187 > --- > drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c | 17 ++++------------- > 1 file changed, 4 insertions(+), 13 deletions(-) > > diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c > index bf0bc46..e50ae8b 100644 > --- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c > +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c > @@ -362,8 +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_BIDIRECTIONAL); > + dma_unmap_sgtable(dev, vmw_tt->sgt, DMA_BIDIRECTIONAL); > vmw_tt->sgt.nents = vmw_tt->sgt.orig_nents; > } > > @@ -383,16 +382,8 @@ static void vmw_ttm_unmap_from_dma(struct vmw_ttm_tt *vmw_tt) > static int vmw_ttm_map_for_dma(struct vmw_ttm_tt *vmw_tt) > { > struct device *dev = vmw_tt->dev_priv->dev->dev; > - int ret; > - > - ret = dma_map_sg(dev, vmw_tt->sgt.sgl, vmw_tt->sgt.orig_nents, > - DMA_BIDIRECTIONAL); > - if (unlikely(ret == 0)) > - return -ENOMEM; > > - vmw_tt->sgt.nents = ret; > - > - return 0; > + return dma_map_sgtable(dev, vmw_tt->sgt, DMA_BIDIRECTIONAL); > } > > /** > @@ -449,10 +440,10 @@ 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; >
diff --git a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c index bf0bc46..e50ae8b 100644 --- a/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c +++ b/drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c @@ -362,8 +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_BIDIRECTIONAL); + dma_unmap_sgtable(dev, vmw_tt->sgt, DMA_BIDIRECTIONAL); vmw_tt->sgt.nents = vmw_tt->sgt.orig_nents; } @@ -383,16 +382,8 @@ static void vmw_ttm_unmap_from_dma(struct vmw_ttm_tt *vmw_tt) static int vmw_ttm_map_for_dma(struct vmw_ttm_tt *vmw_tt) { struct device *dev = vmw_tt->dev_priv->dev->dev; - int ret; - - ret = dma_map_sg(dev, vmw_tt->sgt.sgl, vmw_tt->sgt.orig_nents, - DMA_BIDIRECTIONAL); - if (unlikely(ret == 0)) - return -ENOMEM; - vmw_tt->sgt.nents = ret; - - return 0; + return dma_map_sgtable(dev, vmw_tt->sgt, DMA_BIDIRECTIONAL); } /** @@ -449,10 +440,10 @@ 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;
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 the 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. A common mistake was to ignore a result of the dma_map_sg function and don't use the sg_table->orig_nents at all. To avoid such issues, lets use common dma-mapping wrappers operating directly on the struct sg_table objects and adjust references to the nents and orig_nents respectively. Signed-off-by: Marek Szyprowski <m.szyprowski@samsung.com> --- For more information, see '[PATCH v3 00/25] DRM: fix struct sg_table nents vs. orig_nents misuse' thread: https://lkml.org/lkml/2020/5/5/187 --- drivers/gpu/drm/vmwgfx/vmwgfx_ttm_buffer.c | 17 ++++------------- 1 file changed, 4 insertions(+), 13 deletions(-)