linux-kernel - [PATCH v3 1/2] KVM: arm64: Support FFA_MSG_SEND_DIRECT

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Message-Id: <20251119-host-direct-messages-v3-1-c74d04944b26@google.com>
Date: Wed, 19 Nov 2025 02:07:53 +0000
From: Per Larsen via B4 Relay <devnull+perlarsen.google.com@...nel.org>
To: Marc Zyngier <maz@...nel.org>, 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>, 
 Yeoreum Yun <yeoreum.yun@....com>, Ben Horgan <ben.horgan@....com>, 
 Oliver Upton <oupton@...nel.org>
Cc: Armelle Laine <armellel@...gle.com>, 
 Sebastien Ene <sebastianene@...gle.com>, 
 linux-arm-kernel@...ts.infradead.org, kvmarm@...ts.linux.dev, 
 linux-kernel@...r.kernel.org, Per Larsen <perlarsen@...gle.com>
Subject: [PATCH v3 1/2] KVM: arm64: Support FFA_MSG_SEND_DIRECT_REQ in host
 handler

From: Sebastian Ene <sebastianene@...gle.com>

Allow direct messages to be forwarded from the host. The host should
not be sending framework messages so they are filtered out.

Signed-off-by: Sebastian Ene <sebastianene@...gle.com>
Reviewed-by: Yeoreum Yun <yeoreum.yun@....com>
Signed-off-by: Per Larsen <perlarsen@...gle.com>
---
 arch/arm64/kvm/hyp/nvhe/ffa.c | 22 ++++++++++++++++++++++
 include/linux/arm_ffa.h       |  3 +++
 2 files changed, 25 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 58b7d0c477d7fce235fc70d089d175c7879861b5..a38a3ab497e5eac11777109684a33f02d88d09a1 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -862,6 +862,23 @@ static void do_ffa_part_get(struct arm_smccc_1_2_regs *res,
 	hyp_spin_unlock(&host_buffers.lock);
 }
 
+static void do_ffa_direct_msg(struct arm_smccc_1_2_regs *res,
+			      struct kvm_cpu_context *ctxt,
+			      u64 vm_handle)
+{
+	DECLARE_REG(u32, flags, ctxt, 2);
+
+	struct arm_smccc_1_2_regs *args = (void *)&ctxt->regs.regs[0];
+
+	/* filter out framework messages */
+	if (FIELD_GET(FFA_MSG_FLAGS_MSG_TYPE, flags)) {
+		ffa_to_smccc_error(res, FFA_RET_INVALID_PARAMETERS);
+		return;
+	}
+
+	arm_smccc_1_2_smc(args, res);
+}
+
 bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
 {
 	struct arm_smccc_1_2_regs res;
@@ -920,6 +937,11 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt, u32 func_id)
 	case FFA_PARTITION_INFO_GET:
 		do_ffa_part_get(&res, host_ctxt);
 		goto out_handled;
+	case FFA_MSG_SEND_DIRECT_REQ:
+	case FFA_FN64_MSG_SEND_DIRECT_REQ:
+
+		do_ffa_direct_msg(&res, host_ctxt, HOST_FFA_ID);
+		goto out_handled;
 	}
 
 	if (ffa_call_supported(func_id))
diff --git a/include/linux/arm_ffa.h b/include/linux/arm_ffa.h
index 81e603839c4a51873090b7e22edbe7b33a7e94df..d209d0cdac1eb804be01e4607acac8f76cc99e40 100644
--- a/include/linux/arm_ffa.h
+++ b/include/linux/arm_ffa.h
@@ -130,6 +130,9 @@
 #define FFA_FEAT_RXTX_MIN_SZ_16K	2
 #define FFA_FEAT_RXTX_MIN_SZ_MASK	GENMASK(1, 0)
 
+/* FFA message flags */
+#define FFA_MSG_FLAGS_MSG_TYPE		BIT(31)
+
 /* FFA Bus/Device/Driver related */
 struct ffa_device {
 	u32 id;

-- 
2.52.0.rc1.455.g30608eb744-goog