[PATCH RFC 18/22] KVM: x86: hyper-v: Honor HV_SIGNAL_EVENTS privilege bit

[Vitaly Kuznetsov]

Hyper-V partition must possess 'HV_SIGNAL_EVENTS' privilege to issue
HVCALL_SIGNAL_EVENT hypercalls.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
 arch/x86/kvm/hyperv.c | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 6e4bf1da9dcf..b661f92d90c8 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2120,6 +2120,12 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 		kvm_vcpu_on_spin(vcpu, true);
 		break;
 	case HVCALL_SIGNAL_EVENT:
+		if (unlikely(!(hv_vcpu->cpuid_cache.features_ebx &
+			       HV_SIGNAL_EVENTS))) {
+			ret = HV_STATUS_ACCESS_DENIED;
+			break;
+		}
+
 		if (unlikely(rep)) {
 			ret = HV_STATUS_INVALID_HYPERCALL_INPUT;
 			break;
-- 
2.30.2