[PATCH v8 00/23] dma-mapping: Track shared DMA state through direct, pool and swiotlb paths

This series tracks confidential-computing shared DMA state 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 separates mapping and allocation state:
- DMA_ATTR_CC_SHARED describes the DMA address attribute requested for a
  mapping. It tells the DMA mapping path that the DMA address must target
  shared/decrypted memory.
- __DMA_ATTR_ALLOC_CC_SHARED is an internal DMA-mapping attribute used only
  by allocation paths after the DMA core decides that the backing pages
  must be allocated as shared/decrypted memory.

The series:
- moves swiotlb-backed allocations out of __dma_direct_alloc_pages(),
- uses __DMA_ATTR_ALLOC_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
- reports CC_ATTR_GUEST_MEM_ENCRYPT for arm64 Realms, powerpc secure
  guests, and s390 protected virtualization guests.

Dependency:
This series depends on the pKVM changes posted at:
https://lore.kernel.org/all/[email protected]

Please merge this series only after the pKVM changes above are merged.
Otherwise pKVM will be broken.

Changes since v7:
https://lore.kernel.org/all/[email protected]
* Rebased onto dma-mapping-for-next
* Prepared the series on top of the prerequisite pKVM changes, resolving
  conflicts so it can be applied directly to the pKVM topic branch once ready.
  https://git.gitlab.arm.com/linux-arm/linux-cca/-/commits/scratch/pkvm/testing
* Added comments documenting possible follow-up improvements for CC_SHARED
  atomic pools and physical-address-based pool freeing.
* Retained virtual-address-based pool freeing when
  CONFIG_DMA_DIRECT_REMAP is disabled.
* Applied pgprot_decrypted() only when expanding a CC_SHARED atomic pool.

Changes since v6:
https://lore.kernel.org/all/[email protected]
* Rebase onto the latest kernel.
* Add __DMA_ATTR_ALLOC_CC_SHARED for allocation paths. DMA_ATTR_CC_SHARED
  is now used to describe the requested DMA mapping address attribute,
  while __DMA_ATTR_ALLOC_CC_SHARED is used internally when allocating
  shared/decrypted backing pages.
* Report CC_ATTR_GUEST_MEM_ENCRYPT for arm64 Realms, powerpc secure
  guests, and s390 protected virtualization guests.
* Add CC_ATTR_HOST_MEM_ENCRYPT and swiotlb=force fixes.

Changes since v5:
https://lore.kernel.org/all/[email protected]
* Add Tested-by
* Drop the pKVM patch, which has now been posted separately:
  https://lore.kernel.org/all/[email protected]
* 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 protected]
* 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 protected]
* 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 protected]
* 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 protected]
* 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 protected]>
Cc: Marek Szyprowski <[email protected]>
Cc: Will Deacon <[email protected]>
Cc: Marc Zyngier <[email protected]>
Cc: Steven Price <[email protected]>
Cc: Suzuki K Poulose <[email protected]>
Cc: Catalin Marinas <[email protected]>
Cc: Jiri Pirko <[email protected]>
Cc: Jason Gunthorpe <[email protected]>
Cc: Mostafa Saleh <[email protected]>
Cc: Petr Tesarik <[email protected]>
Cc: Alexey Kardashevskiy <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: Xu Yilun <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: Madhavan Srinivasan <[email protected]>
Cc: Michael Ellerman <[email protected]>
Cc: Nicholas Piggin <[email protected]>
Cc: "Christophe Leroy (CS GROUP)" <[email protected]>
Cc: Alexander Gordeev <[email protected]>
Cc: Gerald Schaefer <[email protected]>
Cc: Heiko Carstens <[email protected]>
Cc: Vasily Gorbik <[email protected]>
Cc: Christian Borntraeger <[email protected]>
Cc: Sven Schnelle <[email protected]>
Cc: [email protected]

Aneesh Kumar K.V (Arm) (23):
  dma-direct: return struct page from dma_direct_alloc_from_pool()
  dma-pool: fix page leak in atomic_pool_expand() cleanup
  iommu/dma: Check atomic pool allocation result directly
  dma: free atomic pool pages by physical address
  swiotlb: Preserve allocation virtual address for dynamic pools
  s390: Expose protected virtualization through cc_platform_has()
  dma-direct: swiotlb: handle swiotlb alloc/free outside
    __dma_direct_alloc_pages
  coco: arm64: s390: powerpc: Mark secure guests with
    CC_ATTR_GUEST_MEM_ENCRYPT
  dma-mapping: Add internal shared allocation attribute
  dma-direct: use __DMA_ATTR_ALLOC_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_ALLOC_CC_SHARED
  dma-direct: pass attrs to dma_capable() for DMA_ATTR_CC_SHARED checks
  dma-direct: Move dma_direct_map_phys() to dma/direct.c
  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_ALLOC_CC_SHARED
  dma-direct: rename ret to cpu_addr in alloc helpers
  dma: swiotlb: free dynamic pools from process context
  dma: swiotlb: handle set_memory_decrypted() failures
  swiotlb: remove unused SWIOTLB_FORCE flag

 Documentation/core-api/dma-attributes.rst    |  29 ++
 arch/arm64/mm/init.c                         |   5 +-
 arch/powerpc/platforms/pseries/cc_platform.c |   1 +
 arch/powerpc/platforms/pseries/svm.c         |   2 +-
 arch/s390/Kconfig                            |   1 +
 arch/s390/mm/init.c                          |  17 +-
 arch/x86/kernel/amd_gart_64.c                |  30 +-
 arch/x86/kernel/pci-dma.c                    |   4 +-
 drivers/iommu/dma-iommu.c                    |  20 +-
 drivers/xen/swiotlb-xen.c                    |   8 +-
 include/linux/dma-direct.h                   |  20 +-
 include/linux/dma-map-ops.h                  |   3 +-
 include/linux/dma-mapping.h                  |   8 +
 include/linux/swiotlb.h                      |  25 +-
 include/trace/events/dma.h                   |   3 +-
 kernel/dma/direct.c                          | 326 ++++++++++++++-----
 kernel/dma/direct.h                          |  56 +---
 kernel/dma/mapping.c                         |  25 +-
 kernel/dma/pool.c                            | 237 ++++++++++----
 kernel/dma/swiotlb.c                         | 292 +++++++++++++----
 20 files changed, 810 insertions(+), 302 deletions(-)

-- 
2.43.0