[PATCH v2 0/4] Clear shared pages after private-to-shared conversion

[Steven Price <steven.price@arm.com>]

set_memory_decrypted() doesn't (currently) guarantee to preserve or zero
memory, but both the GICv3 ITS driver and the system_cc_shared dma-buf
heap currently allocate memory with __GFP_ZERO followed by calling
set_memory_decrypted(). On an Arm CCA system with MEC this can cause
ciphertext to be visible to the guest rather than the expected zeros.

Patches 1 and 3 fix this by zeroing after the set_memory_decrypted()
call.

Patches 2 and 4 fix other related bugs that Sashiko found. Patch 2 fixes
the issue that set_memory_decrypted() can be a sleeping call, so moves
the allocation out of an atomic context.

Patch 4 deals with the situation where set_memory_decrypted() fails and
the rollback path could attempt to re-encrypt memory which was never
decrypted.

I've sorted the patches by area, but there's no (semantic) dependency
between them.

Changes in v2:
 * Switched to use BIT(n) rather than 1 << n in the GICv3 change.
 * Added Jason's R-b.
 * Patches 2 and 4 are new.

v1: https://lore.kernel.org/r/20260820105026.53208-1-steven.price@arm.com

Steven Price (4):
  irqchip/gic-v3-its: Zero shared pages after conversion
  irqchip/gic-v3-its: Allocate VPE tables from sleepable context
  dma-buf: heaps: Zero system shared heap pages after conversion
  dma-buf: heaps: Fix shared system heap allocation rollback

 drivers/dma-buf/heaps/system_heap.c | 24 +++++++++++++-----
 drivers/irqchip/irq-gic-v3-its.c    | 39 ++++++++++++++++-------------
 2 files changed, 40 insertions(+), 23 deletions(-)

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2.43.0