[PATCH v2 6/8] dma-direct: make dma_direct_map_phys() honor DMA_ATTR_CC_SHARED

Aneesh Kumar K.V (Arm)
2026-04-20T06:15:03Z

Teach dma_direct_map_phys() to select the DMA address encoding based on
DMA_ATTR_CC_SHARED.

Use phys_to_dma_unencrypted() for decrypted mappings and
phys_to_dma_encrypted() otherwise. If a device requires unencrypted DMA
but the source physical address is still encrypted, force the mapping
through swiotlb so the DMA address and backing memory attributes remain
consistent.

Signed-off-by: Aneesh Kumar K.V (Arm) <aneesh.kumar@kernel.org>
---
kernel/dma/direct.h | 25 ++++++++++++++-----------
1 file changed, 14 insertions(+), 11 deletions(-)

diff --git a/kernel/dma/direct.h b/kernel/dma/direct.h
index 7140c208c123..928671ef01e9 100644
--- a/kernel/dma/direct.h
+++ b/kernel/dma/direct.h
@@ -86,9 +86,14 @@ static inline dma_addr_t dma_direct_map_phys(struct device *dev,
phys_addr_t phys, size_t size, enum dma_data_direction dir,
unsigned long attrs, bool flush)
{
+ bool force_swiotlb_map = false;
dma_addr_t dma_addr;

- if (is_swiotlb_force_bounce(dev)) {
+ /* if phys addr attribute is encrypted but the device is forcing an encrypted dma addr */
+ if (!(attrs & DMA_ATTR_CC_SHARED) && force_dma_unencrypted(dev))
+ force_swiotlb_map = true;
+
+ if (is_swiotlb_force_bounce(dev) || force_swiotlb_map) {
if (!(attrs & DMA_ATTR_CC_SHARED)) {
if (attrs & (DMA_ATTR_MMIO | DMA_ATTR_REQUIRE_COHERENT))
return DMA_MAPPING_ERROR;
@@ -105,18 +110,16 @@ static inline dma_addr_t dma_direct_map_phys(struct device *dev,
goto err_overflow;
} else if (attrs & DMA_ATTR_CC_SHARED) {
dma_addr = phys_to_dma_unencrypted(dev, phys);
- if (unlikely(!dma_capable(dev, dma_addr, size, false)))
- goto err_overflow;
} else {
- dma_addr = phys_to_dma(dev, phys);
- if (unlikely(!dma_capable(dev, dma_addr, size, true)) ||
- dma_kmalloc_needs_bounce(dev, size, dir)) {
- if (is_swiotlb_active(dev) &&
- !(attrs & DMA_ATTR_REQUIRE_COHERENT))
- return swiotlb_map(dev, phys, size, dir, attrs);
+ dma_addr = phys_to_dma_encrypted(dev, phys);
+ }

- goto err_overflow;
- }
+ if (unlikely(!dma_capable(dev, dma_addr, size, true)) ||
+ dma_kmalloc_needs_bounce(dev, size, dir)) {
+ if (is_swiotlb_active(dev) &&
+ !(attrs & DMA_ATTR_REQUIRE_COHERENT))
+ return swiotlb_map(dev, phys, size, dir, attrs);
+ goto err_overflow;
}

if (!dev_is_dma_coherent(dev) &&
--
2.43.0