arm64: KVM: Fix SMCCC handling of unimplemented SMC/HVC calls

commit acfb3b883f6d6a4b5d27ad7fdded11f6a09ae6dd upstream.

KVM doesn't follow the SMCCC when it comes to unimplemented calls,
and inject an UNDEF instead of returning an error. Since firmware
calls are now used for security mitigation, they are becoming more
common, and the undef is counter productive.

Instead, let's follow the SMCCC which states that -1 must be returned
to the caller when getting an unknown function number.

Signed-off-by: Marc Zyngier <marc.zyngier@arm.com>
Signed-off-by: Christoffer Dall <christoffer.dall@linaro.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/arch/arm64/kvm/handle_exit.c b/arch/arm64/kvm/handle_exit.c
index 34b8bd0711e94295b3b8d629e2e032db8d8bce33..e738bff5eec19393cad252850bd52df83ee380a0 100644 (file)
--- a/arch/arm64/kvm/handle_exit.c
+++ b/arch/arm64/kvm/handle_exit.c
@@ -34,7 +34,7 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
 
        ret = kvm_psci_call(vcpu);
        if (ret < 0) {
-               kvm_inject_undefined(vcpu);
+               *vcpu_reg(vcpu, 0) = ~0UL;
                return 1;
        }
 
@@ -43,7 +43,7 @@ static int handle_hvc(struct kvm_vcpu *vcpu, struct kvm_run *run)
 
 static int handle_smc(struct kvm_vcpu *vcpu, struct kvm_run *run)
 {
-       kvm_inject_undefined(vcpu);
+       *vcpu_reg(vcpu, 0) = ~0UL;
        return 1;
 }