[PATCH v3 0/9] dma-mapping: Use DMA_ATTR_CC_SHARED through direct, pool and swiotlb paths

Aneesh Kumar K.V (Arm)
2026-04-27T05:55:23Z

This series propagates DMA_ATTR_CC_SHARED through the dma-direct,
dma-pool, and swiotlb paths so that encrypted and decrypted DMA buffers
are handled consistently.

Today, the direct DMA path mostly relies on force_dma_unencrypted() for
shared/decrypted buffer handling. This series consolidates the
force_dma_unencrypted() checks in the top-level functions and ensures
that the remaining DMA interfaces use DMA attributes to make the correct
decisions.

The series:
- moves swiotlb-backed allocations out of __dma_direct_alloc_pages(),
- propagates DMA_ATTR_CC_SHARED through the dma-direct alloc/free
paths
- teaches the atomic DMA pools to track encrypted versus decrypted
state
- tracks swiotlb pool encryption state and enforces strict pool
selection
- centralizes encrypted/decrypted pgprot handling in dma_pgprot() using
DMA attributes
- passes DMA attributes down to dma_capable() so capability checks can
validate whether the selected DMA address encoding matches
DMA_ATTR_CC_SHARED
- makes dma_direct_map_phys() choose the DMA address encoding from
DMA_ATTR_CC_SHARED and fall back to swiotlb when a shared DMA request
cannot use the direct mapping, which lets arm64 and x86 CCA guests stop
relying on SWIOTLB_FORCE for DMA mappings
- use the selected swiotlb pool state to derive the returned DMA
address.

Changes from v2:
https://lore.kernel.org/all/20260420061415.3650870-1-aneesh.kumar@kernel.org
* pass attrs to dma_capable() and update direct, swiotlb, Xen swiotlb, and
x86 GART paths so the capability checks see the DMA address attr value
DMA_ATTR_CC_SHARED.
* rework dma_direct_map_phys() so DMA_ATTR_CC_SHARED selects
phys_to_dma_unencrypted() while the default path uses
phys_to_dma_encrypted(), with swiotlb fallback when the requested
shared/private state cannot be satisfied by a direct DMA address.
* stop relying on SWIOTLB_FORCE for arm64 and x86 CC guest DMA mappings;
swiotlb is still enabled there, but shared mappings is now selected
through the generic dma_direct_map_phys()/dma_capable() decision instead
of a global force-bounce flag.

Changes from v1:
https://lore.kernel.org/all/20260417085900.3062416-1-aneesh.kumar@kernel.org
* rebased to latest kernel (change from DMA_ATTR_CC_DECRYPTED -> DMA_ATTR_CC_SHARED)
* update the alloc path so DMA_ATTR_CC_SHARED is not a caller-visible attribute.

Cc: Robin Murphy <robin.murphy@arm.com>
Cc: Marek Szyprowski <m.szyprowski@samsung.com>
Cc: Will Deacon <will@kernel.org>
Cc: Marc Zyngier <maz@kernel.org>
Cc: Steven Price <steven.price@arm.com>
Cc: Suzuki K Poulose <Suzuki.Poulose@arm.com>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Jiri Pirko <jiri@resnulli.us>
Cc: Jason Gunthorpe <jgg@ziepe.ca>
Cc: Mostafa Saleh <smostafa@google.com>
Cc: Petr Tesarik <ptesarik@suse.com>
Cc: Alexey Kardashevskiy <aik@amd.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Xu Yilun <yilun.xu@linux.intel.com>

Aneesh Kumar K.V (Arm) (9):
dma-direct: swiotlb: handle swiotlb alloc/free outside
__dma_direct_alloc_pages
dma-direct: use DMA_ATTR_CC_SHARED in alloc/free paths
dma-pool: track decrypted atomic pools and select them via attrs
dma: swiotlb: track pool encryption state and honor DMA_ATTR_CC_SHARED
dma-mapping: make dma_pgprot() honor DMA_ATTR_CC_SHARED
dma-direct: pass attrs to dma_capable() for DMA_ATTR_CC_SHARED checks
dma-direct: make dma_direct_map_phys() honor DMA_ATTR_CC_SHARED
dma-direct: set decrypted flag for remapped DMA allocations
dma-direct: select DMA address encoding from DMA_ATTR_CC_SHARED

arch/arm64/mm/init.c | 4 +-
arch/x86/kernel/amd_gart_64.c | 30 +++---
arch/x86/kernel/pci-dma.c | 4 +-
drivers/iommu/dma-iommu.c | 2 +-
drivers/xen/swiotlb-xen.c | 9 +-
include/linux/dma-direct.h | 19 +++-
include/linux/dma-map-ops.h | 2 +-
include/linux/swiotlb.h | 7 +-
kernel/dma/direct.c | 189 ++++++++++++++++++++++++++--------
kernel/dma/direct.h | 32 +++---
kernel/dma/mapping.c | 16 ++-
kernel/dma/pool.c | 154 +++++++++++++++++----------
kernel/dma/swiotlb.c | 93 +++++++++++++----
13 files changed, 393 insertions(+), 168 deletions(-)

base-commit: dd6c438c3e64a5ff0b5d7e78f7f9be547803ef1b
--
2.43.0