[PATCH v6 06/16] iommu/dma: implement DMA_ATTR_MMIO for iommu_dma_(un)map_phys()

Leon Romanovsky
2025-09-09T13:28:35Z

Make iommu_dma_map_phys() and iommu_dma_unmap_phys() respect
DMA_ATTR_MMIO.

DMA_ATTR_MMIO makes the functions behave the same as
iommu_dma_(un)map_resource():
- No swiotlb is possible
- No cache flushing is done (ATTR_MMIO should not be cached memory)
- prot for iommu_map() has IOMMU_MMIO not IOMMU_CACHE

This is preparation for replacing iommu_dma_map_resource() callers
with iommu_dma_map_phys(DMA_ATTR_MMIO) and removing
iommu_dma_(un)map_resource().

Reviewed-by: Jason Gunthorpe <jgg@nvidia.com>
Signed-off-by: Leon Romanovsky <leonro@nvidia.com>
---
drivers/iommu/dma-iommu.c | 15 +++++++++++----
1 file changed, 11 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/dma-iommu.c b/drivers/iommu/dma-iommu.c
index aea119f32f965..6804aaf034a16 100644
--- a/drivers/iommu/dma-iommu.c
+++ b/drivers/iommu/dma-iommu.c
@@ -1211,16 +1211,19 @@ dma_addr_t iommu_dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
*/
if (dev_use_swiotlb(dev, size, dir) &&
iova_unaligned(iovad, phys, size)) {
+ if (attrs & DMA_ATTR_MMIO)
+ return DMA_MAPPING_ERROR;
+
phys = iommu_dma_map_swiotlb(dev, phys, size, dir, attrs);
if (phys == (phys_addr_t)DMA_MAPPING_ERROR)
return DMA_MAPPING_ERROR;
}

- if (!coherent && !(attrs & DMA_ATTR_SKIP_CPU_SYNC))
+ if (!coherent && !(attrs & (DMA_ATTR_SKIP_CPU_SYNC | DMA_ATTR_MMIO)))
arch_sync_dma_for_device(phys, size, dir);

iova = __iommu_dma_map(dev, phys, size, prot, dma_mask);
- if (iova == DMA_MAPPING_ERROR)
+ if (iova == DMA_MAPPING_ERROR && !(attrs & DMA_ATTR_MMIO))
swiotlb_tbl_unmap_single(dev, phys, size, dir, attrs);
return iova;
}
@@ -1228,10 +1231,14 @@ dma_addr_t iommu_dma_map_phys(struct device *dev, phys_addr_t phys, size_t size,
void iommu_dma_unmap_phys(struct device *dev, dma_addr_t dma_handle,
size_t size, enum dma_data_direction dir, unsigned long attrs)
{
- struct iommu_domain *domain = iommu_get_dma_domain(dev);
phys_addr_t phys;

- phys = iommu_iova_to_phys(domain, dma_handle);
+ if (attrs & DMA_ATTR_MMIO) {
+ __iommu_dma_unmap(dev, dma_handle, size);
+ return;
+ }
+
+ phys = iommu_iova_to_phys(iommu_get_dma_domain(dev), dma_handle);
if (WARN_ON(!phys))
return;

--
2.51.0