[PATCH v2 2/3] KVM: arm64: Actually prevent SMC64 SYSTEM_RESET2 from AArch32

[Oliver Upton]

The SMCCC does not allow the SMC64 calling convention to be used from
AArch32. While KVM checks to see if the calling convention is allowed in
PSCI_1_0_FN_PSCI_FEATURES, it does not actually prevent calls to
unadvertised PSCI v1.0+ functions.

Hoist the check to see if the requested function is allowed into
kvm_psci_call(), thereby preventing SMC64 calls from AArch32 for all
PSCI versions.

Fixes: d43583b890e7 ("KVM: arm64: Expose PSCI SYSTEM_RESET2 call to the guest")
Acked-by: Will Deacon <will at kernel.org>
Reviewed-by: Reiji Watanabe <reijiw at google.com>
Signed-off-by: Oliver Upton <oupton at google.com>
---
 arch/arm64/kvm/psci.c | 14 +++++++++-----
 1 file changed, 9 insertions(+), 5 deletions(-)

diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index cd3ee947485f..d24ccc77500b 100644
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -232,10 +232,6 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 	unsigned long val;
 	int ret = 1;
 
-	val = kvm_psci_check_allowed_function(vcpu, psci_fn);
-	if (val)
-		goto out;
-
 	switch (psci_fn) {
 	case PSCI_0_2_FN_PSCI_VERSION:
 		/*
@@ -303,7 +299,6 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
 		break;
 	}
 
-out:
 	smccc_set_retval(vcpu, val, 0, 0, 0);
 	return ret;
 }
@@ -423,6 +418,15 @@ static int kvm_psci_0_1_call(struct kvm_vcpu *vcpu)
  */
 int kvm_psci_call(struct kvm_vcpu *vcpu)
 {
+	u32 psci_fn = smccc_get_function(vcpu);
+	unsigned long val;
+
+	val = kvm_psci_check_allowed_function(vcpu, psci_fn);
+	if (val) {
+		smccc_set_retval(vcpu, val, 0, 0, 0);
+		return 1;
+	}
+
 	switch (kvm_psci_version(vcpu)) {
 	case KVM_ARM_PSCI_1_1:
 		return kvm_psci_1_x_call(vcpu, 1);
-- 
2.35.1.894.gb6a874cedc-goog