Re: [PATCH 1/2] firmware: arm_ffa: Add FFA_FN64_MEM_RECLAIM2 function ID

Re: [PATCH 1/2] firmware: arm_ffa: Add FFA_FN64_MEM_RECLAIM2 function ID

[Snehal Koukuntla]

On Mon, Sep 21, 2026 at 04:58:41PM +0000, sashiko-bot wrote:
> [Severity: Low]
> Does the missing 32-bit counterpart for FFA_FN64_MEM_RECLAIM2 break
> FFA_FN_NATIVE() compatibility on 32-bit architectures?
> 
> Every other FFA_FN64_ prefix in the header has a 32-bit counterpart. If
> FFA_FN_NATIVE(MEM_RECLAIM2) is ever used on a 32-bit build, it will evaluate
> to FFA_MEM_RECLAIM2 due to the architecture-conditional logic, which does
> not exist here, and would cause a compilation failure.
> 
> For 64-bit exclusive ABIs like FFA_MSG_SEND_DIRECT_REQ2, the convention
> is to omit the FN64_ prefix entirely.

Ack, I will rename this to FFA_MEM_RECLAIM2 in v2 to follow the existing
convention for 64-bit-only ABIs in arm_ffa.h.

Thanks,
Snehal

[PATCH 0/2] KVM: arm64: Support FFA_FN64_MEM_RECLAIM2 in host handler

[Snehal Koukuntla]

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_FN64_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.

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").

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

Snehal Koukuntla (2):
  firmware: arm_ffa: Add FFA_FN64_MEM_RECLAIM2 function ID
  KVM: arm64: Support FFA_FN64_MEM_RECLAIM2 in host handler

 arch/arm64/kvm/hyp/nvhe/ffa.c | 117 ++++++++++++++++++++++++++++++++++
 include/linux/arm_ffa.h       |   1 +
 2 files changed, 118 insertions(+)


base-commit: 23ddf997ab16b5f4aa9f948f5a68f5b35e4e398f
-- 
2.55.0.1082.g2b9226bbc0-goog

[PATCH 1/2] firmware: arm_ffa: Add FFA_FN64_MEM_RECLAIM2 function ID

[Snehal Koukuntla]

FF-A v1.3 ALP5 (DEN0140 rev J) introduces the optional FFA_MEM_RECLAIM2
(0xC4000091) ABI, which enables an Owner to reclaim exclusive access to
a subset of pages of a memory region without requiring the Relayer to
maintain intermediate transaction state.

Add the FFA_FN64_MEM_RECLAIM2 function ID definition to arm_ffa.h.

Link: https://support.arm.com/documentation/den0140/j
Signed-off-by: Snehal Koukuntla <snehalreddy@google.com>
---
 include/linux/arm_ffa.h | 1 +
 1 file changed, 1 insertion(+)

diff --git a/include/linux/arm_ffa.h b/include/linux/arm_ffa.h
index e71d83ee0aef..c78cfd72832a 100644
--- a/include/linux/arm_ffa.h
+++ b/include/linux/arm_ffa.h
@@ -78,6 +78,7 @@
 #define FFA_EL3_INTR_HANDLE		FFA_SMC_32(0x8C)
 #define FFA_MSG_SEND_DIRECT_REQ2	FFA_SMC_64(0x8D)
 #define FFA_MSG_SEND_DIRECT_RESP2	FFA_SMC_64(0x8E)
+#define FFA_FN64_MEM_RECLAIM2		FFA_SMC_64(0x91)
 
 /*
  * For some calls it is necessary to use SMC64 to pass or return 64-bit values.
-- 
2.55.0.1082.g2b9226bbc0-goog

Re: [PATCH 1/2] firmware: arm_ffa: Add FFA_FN64_MEM_RECLAIM2 function ID

[Sudeep Holla]

On Mon, Sep 21, 2026 at 04:47:47PM +0000, Snehal Koukuntla wrote:
> FF-A v1.3 ALP5 (DEN0140 rev J) introduces the optional FFA_MEM_RECLAIM2
> (0xC4000091) ABI, which enables an Owner to reclaim exclusive access to
> a subset of pages of a memory region without requiring the Relayer to
> maintain intermediate transaction state.
> 
> Add the FFA_FN64_MEM_RECLAIM2 function ID definition to arm_ffa.h.
> 

Since the spec is still at ALPHA, I suggest to add RFC in the subject
if you post newer version so that it is *NOT* considered for merging
until spec reaches *BETA*.

-- 
Regards,
Sudeep

Re: [PATCH 1/2] firmware: arm_ffa: Add FFA_FN64_MEM_RECLAIM2 function ID

[Snehal Koukuntla]

Hi Sudeep,

On Tue, Sep 22, 2026 at 01:15:52PM +0100, Sudeep Holla wrote:
> On Mon, Sep 21, 2026 at 04:47:47PM +0000, Snehal Koukuntla wrote:
> > FF-A v1.3 ALP5 (DEN0140 rev J) introduces the optional FFA_MEM_RECLAIM2
> > (0xC4000091) ABI, which enables an Owner to reclaim exclusive access to
> > a subset of pages of a memory region without requiring the Relayer to
> > maintain intermediate transaction state.
> > 
> > Add the FFA_FN64_MEM_RECLAIM2 function ID definition to arm_ffa.h.
> > 
> 
> Since the spec is still at ALPHA, I suggest to add RFC in the subject
> if you post newer version so that it is *NOT* considered for merging
> until spec reaches *BETA*.

Makes sense, I will mark v2 with [RFC PATCH v2] in the subject.

Thanks,
Snehal