Tested-by: Alex Goins agoins@nvidia.com
This change fixes a regression with drm_prime_sg_to_page_addr_arrays() and AMDGPU in v5.9.
Commit 39913934 similarly revamped AMDGPU to use sgtable helper functions. When it changed from dma_map_sg_attrs() to dma_map_sgtable(), as a side effect it started correctly updating sgt->nents to the return value of dma_map_sg_attrs(). However, drm_prime_sg_to_page_addr_arrays() incorrectly uses sgt->nents to iterate over pages, rather than sgt->orig_nents, resulting in it now returning the incorrect number of pages on AMDGPU.
I had written a patch that changes drm_prime_sg_to_page_addr_arrays() to use for_each_sgtable_sg() instead of for_each_sg(), iterating using sgt->orig_nents:
- for_each_sg(sgt->sgl, sg, sgt->nents, count) { + for_each_sgtable_sg(sgt, sg, count) {
This patch takes it further, but still has the effect of fixing the number of pages that drm_prime_sg_to_page_addr_arrays() returns. Something like this should be included in v5.9 to prevent a regression with AMDGPU.
Thanks, Alex
On Wed, 13 May 2020, Marek Szyprowski wrote:
Replace the current hand-crafted code for extracting pages and DMA addresses from the given scatterlist by the much more robust code based on the generic scatterlist iterators and recently introduced sg_table-based wrappers. The resulting code is simple and easy to understand, so the comment describing the old code is no longer needed.
Signed-off-by: Marek Szyprowski m.szyprowski@samsung.com
For more information, see '[PATCH v5 00/38] DRM: fix struct sg_table nents vs. orig_nents misuse' thread: https://lore.kernel.org/linux-iommu/20200513132114.6046-1-m.szyprowski@samsu...
drivers/gpu/drm/drm_prime.c | 47 ++++++++++++++------------------------------- 1 file changed, 14 insertions(+), 33 deletions(-)
diff --git a/drivers/gpu/drm/drm_prime.c b/drivers/gpu/drm/drm_prime.c index 1d2e5fe..dfdf4d4 100644 --- a/drivers/gpu/drm/drm_prime.c +++ b/drivers/gpu/drm/drm_prime.c @@ -985,45 +985,26 @@ struct drm_gem_object *drm_gem_prime_import(struct drm_device *dev, int drm_prime_sg_to_page_addr_arrays(struct sg_table *sgt, struct page **pages, dma_addr_t *addrs, int max_entries) {
- unsigned count;
- struct scatterlist *sg;
- struct page *page;
- u32 page_len, page_index;
- dma_addr_t addr;
- u32 dma_len, dma_index;
- struct sg_dma_page_iter dma_iter;
- struct sg_page_iter page_iter;
- struct page **p = pages;
- dma_addr_t *a = addrs;
- /*
* Scatterlist elements contains both pages and DMA addresses, but* one shoud not assume 1:1 relation between them. The sg->length is* the size of the physical memory chunk described by the sg->page,* while sg_dma_len(sg) is the size of the DMA (IO virtual) chunk* described by the sg_dma_address(sg).*/- page_index = 0;
- dma_index = 0;
- for_each_sg(sgt->sgl, sg, sgt->nents, count) {
page_len = sg->length;page = sg_page(sg);dma_len = sg_dma_len(sg);addr = sg_dma_address(sg);while (pages && page_len > 0) {if (WARN_ON(page_index >= max_entries))
- if (pages) {
for_each_sgtable_page(sgt, &page_iter, 0) {if (p - pages >= max_entries) return -1;
pages[page_index] = page;page++;page_len -= PAGE_SIZE;page_index++;
*p++ = sg_page_iter_page(&page_iter);
while (addrs && dma_len > 0) {if (WARN_ON(dma_index >= max_entries))
- }
- if (addrs) {
for_each_sgtable_dma_page(sgt, &dma_iter, 0) {if (a - addrs >= max_entries) return -1;
addrs[dma_index] = addr;addr += PAGE_SIZE;dma_len -= PAGE_SIZE;dma_index++;
*a++ = sg_page_iter_dma_address(&dma_iter);- return 0;
} EXPORT_SYMBOL(drm_prime_sg_to_page_addr_arrays); -- 1.9.1
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