[Xen-devel] [PATCH 2/4] swiotlb-xen: use ->map_page to implement ->map_sg

[Christoph Hellwig <hch@xxxxxx>]

We can simply loop over the segments and map them, removing lots of
duplicate code.

Signed-off-by: Christoph Hellwig <hch@xxxxxx>
---
 drivers/xen/swiotlb-xen.c | 68 ++++++---------------------------------
 1 file changed, 10 insertions(+), 58 deletions(-)

diff --git a/drivers/xen/swiotlb-xen.c b/drivers/xen/swiotlb-xen.c
index d4bc3aabd44d..97a55c225593 100644
--- a/drivers/xen/swiotlb-xen.c
+++ b/drivers/xen/swiotlb-xen.c
@@ -517,24 +517,8 @@ xen_swiotlb_unmap_sg(struct device *hwdev, struct 
scatterlist *sgl, int nelems,
 
 }
 
-/*
- * Map a set of buffers described by scatterlist in streaming mode for DMA.
- * This is the scatter-gather version of the above xen_swiotlb_map_page
- * interface.  Here the scatter gather list elements are each tagged with the
- * appropriate dma address and length.  They are obtained via
- * sg_dma_{address,length}(SG).
- *
- * NOTE: An implementation may be able to use a smaller number of
- *       DMA address/length pairs than there are SG table elements.
- *       (for example via virtual mapping capabilities)
- *       The routine returns the number of addr/length pairs actually
- *       used, at most nents.
- *
- * Device ownership issues as mentioned above for xen_swiotlb_map_page are the
- * same here.
- */
 static int
-xen_swiotlb_map_sg(struct device *hwdev, struct scatterlist *sgl, int nelems,
+xen_swiotlb_map_sg(struct device *dev, struct scatterlist *sgl, int nelems,
                enum dma_data_direction dir, unsigned long attrs)
 {
        struct scatterlist *sg;
@@ -543,50 +527,18 @@ xen_swiotlb_map_sg(struct device *hwdev, struct 
scatterlist *sgl, int nelems,
        BUG_ON(dir == DMA_NONE);
 
        for_each_sg(sgl, sg, nelems, i) {
-               phys_addr_t paddr = sg_phys(sg);
-               dma_addr_t dev_addr = xen_phys_to_bus(paddr);
-
-               if (swiotlb_force == SWIOTLB_FORCE ||
-                   xen_arch_need_swiotlb(hwdev, paddr, dev_addr) ||
-                   !dma_capable(hwdev, dev_addr, sg->length) ||
-                   range_straddles_page_boundary(paddr, sg->length)) {
-                       phys_addr_t map = swiotlb_tbl_map_single(hwdev,
-                                                                start_dma_addr,
-                                                                sg_phys(sg),
-                                                                sg->length,
-                                                                dir, attrs);
-                       if (map == DMA_MAPPING_ERROR) {
-                               dev_warn(hwdev, "swiotlb buffer is full\n");
-                               /* Don't panic here, we expect map_sg users
-                                  to do proper error handling. */
-                               attrs |= DMA_ATTR_SKIP_CPU_SYNC;
-                               xen_swiotlb_unmap_sg(hwdev, sgl, i, dir, attrs);
-                               sg_dma_len(sgl) = 0;
-                               return 0;
-                       }
-                       dev_addr = xen_phys_to_bus(map);
-                       xen_dma_map_page(hwdev, pfn_to_page(map >> PAGE_SHIFT),
-                                               dev_addr,
-                                               map & ~PAGE_MASK,
-                                               sg->length,
-                                               dir,
-                                               attrs);
-                       sg->dma_address = dev_addr;
-               } else {
-                       /* we are not interested in the dma_addr returned by
-                        * xen_dma_map_page, only in the potential cache 
flushes executed
-                        * by the function. */
-                       xen_dma_map_page(hwdev, pfn_to_page(paddr >> 
PAGE_SHIFT),
-                                               dev_addr,
-                                               paddr & ~PAGE_MASK,
-                                               sg->length,
-                                               dir,
-                                               attrs);
-                       sg->dma_address = dev_addr;
-               }
+               sg->dma_address = xen_swiotlb_map_page(dev, sg_page(sg),
+                               sg->offset, sg->length, dir, attrs);
+               if (sg->dma_address == DMA_MAPPING_ERROR)
+                       goto out_unmap;
                sg_dma_len(sg) = sg->length;
        }
+
        return nelems;
+out_unmap:
+       xen_swiotlb_unmap_sg(dev, sgl, i, dir, attrs | DMA_ATTR_SKIP_CPU_SYNC);
+       sg_dma_len(sgl) = 0;
+       return 0;
 }
 
 /*
-- 
2.20.1


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