[PATCH RFC 19/22] KVM: x86: hyper-v: Honor HV_DEBUGGING privilege bit

[Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>]

Hyper-V partition must possess 'HV_DEBUGGING' privilege to issue
HVCALL_POST_DEBUG_DATA/HVCALL_RETRIEVE_DEBUG_DATA/
HVCALL_RESET_DEBUG_SESSION 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 b661f92d90c8..7cb1dd1a9fc1 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2211,6 +2211,12 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 			break;
 		}
 
+		if (unlikely(!(hv_vcpu->cpuid_cache.features_ebx &
+			       HV_DEBUGGING))) {
+			ret = HV_STATUS_ACCESS_DENIED;
+			break;
+		}
+
 		if (!(syndbg->options & HV_X64_SYNDBG_OPTION_USE_HCALLS)) {
 			ret = HV_STATUS_OPERATION_DENIED;
 			break;
-- 
2.30.2