On 4/29/25 13:53, Leon Romanovsky wrote:
On Tue, Apr 29, 2025 at 12:58:18PM +0800, Baolu Lu wrote:
On 4/28/25 17:22, Leon Romanovsky wrote:
From: Christoph Hellwig<hch@xxxxxx>
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@xxxxxx>
Tested-by: Jens Axboe<axboe@xxxxxxxxx>
Reviewed-by: Luis Chamberlain<mcgrof@xxxxxxxxxx>
Signed-off-by: Leon Romanovsky<leonro@xxxxxxxxxx>
Reviewed-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
with a nit below ...
---
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 d3211a8d755e..d7684024c439 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1138,6 +1138,43 @@ 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 (phys_addr_t)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 != (phys_addr_t)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)
@@ -1151,42 +1188,14 @@ 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)) {
... Is it better to move this check into the helper? Simply no-op if a
bounce page is not needed:
if (!dev_use_swiotlb(dev, size, dir) ||
!iova_offset(iovad, phys | size))
return phys;
Am I missing something? iommu_dma_map_page() has more code after this
check, so it is not correct to return immediately:
1189 dma_addr_t iommu_dma_map_page(struct device *dev, struct page *page,
1190 unsigned long offset, size_t size, enum dma_data_direction dir,
1191 unsigned long attrs)
1192 {
<...>
1201 /*
1202 * If both the physical buffer start address and size are page aligned,
1203 * we don't need to use a bounce page.
1204 */
1205 if (dev_use_swiotlb(dev, size, dir) &&
1206 iova_unaligned(iovad, phys, size)) {
1207 phys = iommu_dma_map_swiotlb(dev, phys, size, dir, attrs);
1208 if (phys == (phys_addr_t)DMA_MAPPING_ERROR)
1209 return DMA_MAPPING_ERROR;
1210 }
1211
1212 if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
1213 arch_sync_dma_for_device(phys, size, dir);
1214
1215 iova = __iommu_dma_map(dev, phys, size, prot, dma_mask);
1216 if (iova == DMA_MAPPING_ERROR)
1217 swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
1218 return iova;
1219 }
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)
{
<...>
/*
* 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))
return phys;
<...>
}
Then,
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)
{
<...>
phys = iommu_dma_map_swiotlb(dev, phys, size, dir, attrs);
if (phys == (phys_addr_t)DMA_MAPPING_ERROR)
return DMA_MAPPING_ERROR;
<...>
}
Thanks,
baolu
