[PATCH 05/12] KVM: arm64: Handle FFA_FEATURES call from the host

[Quentin Perret <qperret@google.com>]

From: Fuad Tabba <tabba@google.com>

Filter out advertising unsupported features, and only advertise
features and properties that are supported by the hypervisor proxy.

Signed-off-by: Fuad Tabba <tabba@google.com>
Signed-off-by: Quentin Perret <qperret@google.com>
---
 arch/arm64/kvm/hyp/nvhe/ffa.c | 44 +++++++++++++++++++++++++++++++++++
 1 file changed, 44 insertions(+)

diff --git a/arch/arm64/kvm/hyp/nvhe/ffa.c b/arch/arm64/kvm/hyp/nvhe/ffa.c
index 969d72390844..d199f868583e 100644
--- a/arch/arm64/kvm/hyp/nvhe/ffa.c
+++ b/arch/arm64/kvm/hyp/nvhe/ffa.c
@@ -45,6 +45,16 @@ static void ffa_to_smccc_error(struct arm_smccc_res *res, u64 ffa_errno)
 	};
 }
 
+static void ffa_to_smccc_res_prop(struct arm_smccc_res *res, int ret, u64 prop)
+{
+	if (ret == FFA_RET_SUCCESS) {
+		*res = (struct arm_smccc_res) { .a0 = FFA_SUCCESS,
+						.a2 = prop };
+	} else {
+		ffa_to_smccc_error(res, ret);
+	}
+}
+
 static void ffa_set_retval(struct kvm_cpu_context *ctxt,
 			   struct arm_smccc_res *res)
 {
@@ -89,6 +99,35 @@ static bool ffa_call_unsupported(u64 func_id)
 	return false;
 }
 
+static bool do_ffa_features(struct arm_smccc_res *res,
+			    struct kvm_cpu_context *ctxt)
+{
+	DECLARE_REG(u32, id, ctxt, 1);
+	u64 prop = 0;
+	int ret = 0;
+
+	if (ffa_call_unsupported(id)) {
+		ret = FFA_RET_NOT_SUPPORTED;
+		goto out_handled;
+	}
+
+	switch (id) {
+	case FFA_MEM_SHARE:
+	case FFA_FN64_MEM_SHARE:
+	case FFA_MEM_LEND:
+	case FFA_FN64_MEM_LEND:
+		ret = FFA_RET_SUCCESS;
+		prop = 0; /* No support for dynamic buffers */
+		goto out_handled;
+	default:
+		return false;
+	}
+
+out_handled:
+	ffa_to_smccc_res_prop(res, ret, prop);
+	return true;
+}
+
 bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 {
 	DECLARE_REG(u64, func_id, host_ctxt, 0);
@@ -98,6 +137,10 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 		return false;
 
 	switch (func_id) {
+	case FFA_FEATURES:
+		if (!do_ffa_features(&res, host_ctxt))
+			return false;
+		goto out_handled;
 	/* Memory management */
 	case FFA_FN64_RXTX_MAP:
 	case FFA_RXTX_UNMAP:
@@ -114,6 +157,7 @@ bool kvm_host_ffa_handler(struct kvm_cpu_context *host_ctxt)
 		return false; /* Pass through */
 
 	ffa_to_smccc_error(&res, FFA_RET_NOT_SUPPORTED);
+out_handled:
 	ffa_set_retval(host_ctxt, &res);
 	return true;
 }
-- 
2.38.1.431.g37b22c650d-goog