KVM: arm64: Actually prevent SMC64 SYSTEM_RESET2 from AArch32

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@kernel.org>
Reviewed-by: Reiji Watanabe <reijiw@google.com>
Signed-off-by: Oliver Upton <oupton@google.com>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20220322183538.2757758-3-oupton@google.com

diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index a76d03d..faf403a 100644 (file)
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -231,10 +231,6 @@ 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:
                /*
@@ -302,7 +298,6 @@ static int kvm_psci_0_2_call(struct kvm_vcpu *vcpu)
                break;
        }
 
-out:
        smccc_set_retval(vcpu, val, 0, 0, 0);
        return ret;
 }
@@ -422,6 +417,15 @@ 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);