[PATCH v2 10/13] KVM: arm64: Return NOT_SUPPORTED to guest for unknown PSCI version

Oliver Upton
2023-03-30T15:50:26Z

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>
---
arch/arm64/kvm/psci.c | 7 +++++--
1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/arch/arm64/kvm/psci.c b/arch/arm64/kvm/psci.c
index 7fbc4c1b9df0..aff54b106c30 100644
--- 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;
}
}
--
2.40.0.348.gf938b09366-goog