Subject: [PATCH v6 00/20] dma-mapping: Use DMA_ATTR_CC_SHARED through direct, pool and swiotlb paths

From: "Aneesh Kumar K.V (Arm)" <[email-masked]>
Date: Thu, 4 Jun 2026 14:09:39 +0530

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 since v5:
https://lore.kernel.org/all/[email-masked]
* Add Tested-by
* Drop the pKVM patch, which has now been posted separately:
  https://lore.kernel.org/all/[email-masked]
* Remove the DO_NOT_MERGE tag from the s390 change.
* Add a patch to drop the SWIOTLB_FORCE flag.
* Rebase onto the latest kernel.

Changes since v4:
https://lore.kernel.org/all/[email-masked]
* Add new patches based on Sashiko review:
  swiotlb: Preserve allocation virtual address for dynamic pools
  dma: free atomic pool pages by physical address
  dma: swiotlb: handle set_memory_decrypted() failures
  dma: swiotlb: free dynamic pools from process context
  iommu/dma: Check atomic pool allocation result directly
* Include pKVM and s390 changes as dependent patches. These are not yet
  ready to merge and are waiting for subsystem testing feedback.
* Drop the AMD GART patch because it requires wider testing.
* Update swiotlb_tbl_map_single() to take attrs by reference.
* Switch swiotlb_free() to use rcu_work.
* Avoid calling swiotlb_find_pool() multiple times in the free path.
* Make DMA_ATTR_MMIO imply DMA_ATTR_CC_SHARED for devices requiring unencrypted DMA.

Changes from v3:
https://lore.kernel.org/all/[email-masked]
* Handle DMA_ATTR_MMIO correctly in dma_direct_map_phys()
* Address most of sashiko review
* Rebase to latest kernel
* drop SWIOTLB_FORCE for s390 and powerpc secure guest.

Changes from v2:
https://lore.kernel.org/all/[email-masked]
* 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/[email-masked]
* 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 <[email-masked]>
Cc: Marek Szyprowski <[email-masked]>
Cc: Will Deacon <[email-masked]>
Cc: Marc Zyngier <[email-masked]>
Cc: Steven Price <[email-masked]>
Cc: Suzuki K Poulose <[email-masked]>
Cc: Catalin Marinas <[email-masked]>
Cc: Jiri Pirko <[email-masked]>
Cc: Jason Gunthorpe <[email-masked]>
Cc: Mostafa Saleh <[email-masked]>
Cc: Petr Tesarik <[email-masked]>
Cc: Alexey Kardashevskiy <[email-masked]>
Cc: Dan Williams <[email-masked]>
Cc: Xu Yilun <[email-masked]>
Cc: [email-masked]
Cc: [email-masked]
Cc: Madhavan Srinivasan <[email-masked]>
Cc: Michael Ellerman <[email-masked]>
Cc: Nicholas Piggin <[email-masked]>
Cc: "Christophe Leroy (CS GROUP)" <[email-masked]>
Cc: Alexander Gordeev <[email-masked]>
Cc: Gerald Schaefer <[email-masked]>
Cc: Heiko Carstens <[email-masked]>
Cc: Vasily Gorbik <[email-masked]>
Cc: Christian Borntraeger <[email-masked]>
Cc: Sven Schnelle <[email-masked]>
Cc: [email-masked]

Aneesh Kumar K.V (Arm) (20):
  s390: Expose protected virtualization through cc_platform_has()
  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: pass mapping attributes by reference
  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
  dma-pool: fix page leak in atomic_pool_expand() cleanup
  dma-direct: rename ret to cpu_addr in alloc helpers
  dma-direct: return struct page from dma_direct_alloc_from_pool()
  iommu/dma: Check atomic pool allocation result directly
  dma: swiotlb: free dynamic pools from process context
  dma: swiotlb: handle set_memory_decrypted() failures
  dma: free atomic pool pages by physical address
  swiotlb: Preserve allocation virtual address for dynamic pools
  swiotlb: remove unused SWIOTLB_FORCE flag

 arch/arm64/mm/init.c                 |   4 +-
 arch/powerpc/platforms/pseries/svm.c |   2 +-
 arch/s390/Kconfig                    |   1 +
 arch/s390/mm/init.c                  |  16 +-
 arch/x86/kernel/amd_gart_64.c        |  30 +--
 arch/x86/kernel/pci-dma.c            |   4 +-
 drivers/iommu/dma-iommu.c            |  15 +-
 drivers/xen/swiotlb-xen.c            |   8 +-
 include/linux/dma-direct.h           |  20 +-
 include/linux/dma-map-ops.h          |   3 +-
 include/linux/swiotlb.h              |  21 +-
 kernel/dma/direct.c                  | 275 +++++++++++++++++++--------
 kernel/dma/direct.h                  |  47 ++---
 kernel/dma/mapping.c                 |  16 +-
 kernel/dma/pool.c                    | 221 +++++++++++++++------
 kernel/dma/swiotlb.c                 | 273 ++++++++++++++++++++------
 16 files changed, 692 insertions(+), 264 deletions(-)

base-commit: ba3e43a9e601636f5edb54e259a74f96ca3b8fd8
-- 
2.43.0