linux-kernel - [PATCH v8 5/7] KVM: arm64: Mask response to FFA

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Message-Id: <20250719-virtio-msg-ffa-v8-5-03e8e8dbe856@google.com>
Date: Sat, 19 Jul 2025 02:11:27 +0000
From: Per Larsen via B4 Relay <devnull+perlarsen.google.com@...nel.org>
To: Marc Zyngier <maz@...nel.org>, Oliver Upton <oliver.upton@...ux.dev>, 
 Joey Gouly <joey.gouly@....com>, Suzuki K Poulose <suzuki.poulose@....com>, 
 Zenghui Yu <yuzenghui@...wei.com>, 
 Catalin Marinas <catalin.marinas@....com>, Will Deacon <will@...nel.org>, 
 Sudeep Holla <sudeep.holla@....com>
Cc: linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, ahomescu@...gle.com, armellel@...gle.com, 
 arve@...roid.com, ayrton@...gle.com, qperret@...gle.com, 
 sebastianene@...gle.com, qwandor@...gle.com, 
 Per Larsen <perlarsen@...gle.com>
Subject: [PATCH v8 5/7] KVM: arm64: Mask response to FFA_FEATURE call

From: Per Larsen <perlarsen@...gle.com>

The minimum size and alignment boundary for FFA_RXTX_MAP is returned in
bit[1:0]. Mask off any other bits in w2 when reading the minimum buffer
size in hyp_ffa_post_init.

Signed-off-by: Per Larsen <perlarsen@...gle.com>
---
 arch/arm64/kvm/hyp/nvhe/ffa.c | 2 +-
 include/linux/arm_ffa.h       | 1 +
 2 files changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 5a173ea481940236356e2bc4248d094a858a0923..2cbecc9af5d27a9e7c8497001cf9b0987c72bdb4 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -733,7 +733,7 @@ static int hyp_ffa_post_init(void)
 	if (res.a0 != FFA_SUCCESS)
 		return -EOPNOTSUPP;
 
-	switch (res.a2) {
+	switch (res.a2 & FFA_FEAT_RXTX_MIN_SZ_MASK) {
 	case FFA_FEAT_RXTX_MIN_SZ_4K:
 		min_rxtx_sz = SZ_4K;
 		break;
diff --git a/include/linux/arm_ffa.h b/include/linux/arm_ffa.h
index e1634897e159cdc208931938649eb0fb04d5a070..cd7ee4df9045dceca1c4e0dca2d533b770b1b056 100644
--- a/include/linux/arm_ffa.h
+++ b/include/linux/arm_ffa.h
@@ -128,6 +128,7 @@
 #define FFA_FEAT_RXTX_MIN_SZ_4K		0
 #define FFA_FEAT_RXTX_MIN_SZ_64K	1
 #define FFA_FEAT_RXTX_MIN_SZ_16K	2
+#define FFA_FEAT_RXTX_MIN_SZ_MASK	GENMASK(1, 0)
 
 /* FFA Bus/Device/Driver related */
 struct ffa_device {

-- 
2.50.0.727.gbf7dc18ff4-goog