[PATCH v4 07/18] iommu/dma: Factor out a iommu_dma_map_swiotlb helper

Leon Romanovsky
2024-12-05T14:29:20Z

From: Christoph Hellwig <hch@lst.de>

Split the iommu logic from iommu_dma_map_page into a separate helper.
This not only keeps the code neatly separated, but will also allow for
reuse in another caller.

Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
drivers/iommu/dma-iommu.c | 73 ++++++++++++++++++++++-----------------
1 file changed, 41 insertions(+), 32 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index 127150f63c95..e1eaad500d27 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1161,6 +1161,43 @@ void iommu_dma_sync_sg_for_device(struct device *dev, struct scatterlist *sgl,
arch_sync_dma_for_device(sg_phys(sg), sg->length, dir);
}

+static phys_addr_t iommu_dma_map_swiotlb(struct device *dev, phys_addr_t phys,
+ size_t size, enum dma_data_direction dir, unsigned long attrs)
+{
+ struct iommu_domain *domain = iommu_get_dma_domain(dev);
+ struct iova_domain *iovad = &domain->iova_cookie->iovad;
+
+ if (!is_swiotlb_active(dev)) {
+ dev_warn_once(dev, "DMA bounce buffers are inactive, unable to map unaligned transaction.\n");
+ return DMA_MAPPING_ERROR;
+ }
+
+ trace_swiotlb_bounced(dev, phys, size);
+
+ phys = swiotlb_tbl_map_single(dev, phys, size, iova_mask(iovad), dir,
+ attrs);
+
+ /*
+ * Untrusted devices should not see padding areas with random leftover
+ * kernel data, so zero the pre- and post-padding.
+ * swiotlb_tbl_map_single() has initialized the bounce buffer proper to
+ * the contents of the original memory buffer.
+ */
+ if (phys != DMA_MAPPING_ERROR && dev_is_untrusted(dev)) {
+ size_t start, virt = (size_t)phys_to_virt(phys);
+
+ /* Pre-padding */
+ start = iova_align_down(iovad, virt);
+ memset((void *)start, 0, virt - start);
+
+ /* Post-padding */
+ start = virt + size;
+ memset((void *)start, 0, iova_align(iovad, start) - start);
+ }
+
+ return phys;
+}
+
dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
unsigned long offset, size_t size, enum dma_data_direction dir,
unsigned long attrs)
@@ -1174,42 +1211,14 @@ dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
dma_addr_t iova, dma_mask = dma_get_mask(dev);

/*
- * If both the physical buffer start address and size are
- * page aligned, we don't need to use a bounce page.
+ * If both the physical buffer start address and size are page aligned,
+ * we don't need to use a bounce page.
*/
if (dev_use_swiotlb(dev, size, dir) &&
iova_offset(iovad, phys | size)) {
- if (!is_swiotlb_active(dev)) {
- dev_warn_once(dev, "DMA bounce buffers are inactive, unable to map unaligned transaction.\n");
- return DMA_MAPPING_ERROR;
- }
-
- trace_swiotlb_bounced(dev, phys, size);
-
- phys = swiotlb_tbl_map_single(dev, phys, size,
- iova_mask(iovad), dir, attrs);
-
+ phys = iommu_dma_map_swiotlb(dev, phys, size, dir, attrs);
if (phys == DMA_MAPPING_ERROR)
- return DMA_MAPPING_ERROR;
-
- /*
- * Untrusted devices should not see padding areas with random
- * leftover kernel data, so zero the pre- and post-padding.
- * swiotlb_tbl_map_single() has initialized the bounce buffer
- * proper to the contents of the original memory buffer.
- */
- if (dev_is_untrusted(dev)) {
- size_t start, virt = (size_t)phys_to_virt(phys);
-
- /* Pre-padding */
- start = iova_align_down(iovad, virt);
- memset((void *)start, 0, virt - start);
-
- /* Post-padding */
- start = virt + size;
- memset((void *)start, 0,
- iova_align(iovad, start) - start);
- }
+ return phys;
}

if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
--
2.47.0