[RFC PATCH v2 0/2] KVM: arm64: Support FFA_MEM_RECLAIM2 in host handler

[Snehal Koukuntla <snehalreddy@google.com>]

The Arm Firmware Framework for Arm A-profile (FF-A) v1.3 ALP5
specification (DEN0140 rev J) [1] introduces the optional
FFA_MEM_RECLAIM2 (0xC4000091) ABI.

Reclaiming large memory regions with the existing FFA_MEM_RECLAIM ABI
can take significant time, or relies on a stateful time-slicing
mechanism in the Relayer. FFA_MEM_RECLAIM2 allows an Owner to reclaim
exclusive access to a subset of pages from a shared or lent memory
region by passing an array of constituent memory region descriptors in
its TX buffer along with a starting descriptor byte offset and initial
page index. The Relayer returns the number of 4K pages reclaimed in
that invocation without maintaining intermediate transaction state.

This series adds the FFA_MEM_RECLAIM2 function ID definition and
implements host proxy support in the pKVM nVHE FF-A handler, unsharing
the reclaimed pages in the host stage-2 page tables upon a successful
reclaim response from EL3/SPMD.

As the FF-A v1.3 specification is still at ALPHA, this series is
posted as an RFC and is not intended for merging until the
specification reaches BETA.

This series is based on kvmarm/next, as Patch 2 uses
ffa_check_unused_args_sbz() introduced in commit 3e9df0b0ebd5
("KVM: arm64: Enforce strict SBZ checks in the FF-A proxy").

Changes in v2:
- Mark as RFC until the FF-A v1.3 specification reaches BETA (Sudeep)
- Rename FFA_FN64_MEM_RECLAIM2 to FFA_MEM_RECLAIM2 (sashiko)
- Check total_pages against the sum of constituent pg_cnt (Vincent)
- Simplify the flags and offset alignment checks (Vincent)
- Rebase on latest kvmarm/next
- Link to v1: https://lore.kernel.org/r/20260921164748.2958578-1-snehalreddy@google.com

[1] https://support.arm.com/documentation/den0140/j

Snehal Koukuntla (2):
  firmware: arm_ffa: Add FFA_MEM_RECLAIM2 function ID
  KVM: arm64: Support FFA_MEM_RECLAIM2 in host handler

 arch/arm64/kvm/hyp/nvhe/ffa.c | 126 ++++++++++++++++++++++++++++++++++
 include/linux/arm_ffa.h       |   1 +
 2 files changed, 127 insertions(+)


base-commit: dd0bc00e3e9201fd49b62ff9cc07890c89003afe
-- 
2.56.0.176.g3575e65682-goog