KVM: arm64: Return NOT_SUPPORTED to guest for unknown PSCI version

A subsequent change to KVM will allow negative returns from SMCCC
handlers to exit to userspace. Make way for this change by explicitly
returning SMCCC_RET_NOT_SUPPORTED to the guest if the VM is configured
to use an unknown PSCI version. Add a WARN since this is undoubtedly a
KVM bug.

Signed-off-by: Oliver Upton <oliver.upton@linux.dev>
Signed-off-by: Marc Zyngier <maz@kernel.org>
Link: https://lore.kernel.org/r/20230404154050.2270077-11-oliver.upton@linux.dev

diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index 7fbc4c1..aff54b1 100644 (file)
--- a/arch/arm64/kvm/psci.c
+++ b/arch/arm64/kvm/psci.c
@@ -435,6 +435,7 @@ 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);
+       int version = kvm_psci_version(vcpu);
        unsigned long val;
 
        val = kvm_psci_check_allowed_function(vcpu, psci_fn);
@@ -443,7 +444,7 @@ int kvm_psci_call(struct kvm_vcpu *vcpu)
                return 1;
        }
 
-       switch (kvm_psci_version(vcpu)) {
+       switch (version) {
        case KVM_ARM_PSCI_1_1:
                return kvm_psci_1_x_call(vcpu, 1);
        case KVM_ARM_PSCI_1_0:
@@ -453,6 +454,8 @@ int kvm_psci_call(struct kvm_vcpu *vcpu)
        case KVM_ARM_PSCI_0_1:
                return kvm_psci_0_1_call(vcpu);
        default:
-               return -EINVAL;
+               WARN_ONCE(1, "Unknown PSCI version %d", version);
+               smccc_set_retval(vcpu, SMCCC_RET_NOT_SUPPORTED, 0, 0, 0);
+               return 1;
        }
 }