drm/prime: use dma length macro when mapping sg

As dma_map_sg can reorganize scatter-gather lists in a
way that can cause some later segments to be empty we should
always use the sg_dma_len macro to fetch the actual length.

This could now be 0 and not need to be mapped to a page or
address array

Fixes: be62dbf554c5 ("iommu/amd: Convert AMD iommu driver to the dma-iommu api")
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=206461
Bug: https://bugzilla.kernel.org/show_bug.cgi?id=206895
Bug: https://gitlab.freedesktop.org/drm/amd/issues/1056
Signed-off-by: Shane Francis <bigbeeshane@gmail.com>
Reviewed-by: Michael J. Ruhl <michael.j.ruhl@intel.com>
Signed-off-by: Alex Deucher <alexander.deucher@amd.com>
Link: https://patchwork.freedesktop.org/patch/msgid/20200325090741.21957-2-bigbeeshane@gmail.com
Cc: stable@vger.kernel.org

diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c
index 86d9b0e..1de2cde 100644 (file)
--- a/drivers/gpu/drm/drm_prime.c
+++ b/drivers/gpu/drm/drm_prime.c
@@ -967,7 +967,7 @@ int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages,
 
        index = 0;
        for_each_sg(sgt->sgl, sg, sgt->nents, count) {
-               len = sg->length;
+               len = sg_dma_len(sg);
                page = sg_page(sg);
                addr = sg_dma_address(sg);