linux-kernel - [PATCH v2 24/30] KVM: x86: hyper-v: Honor HV

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Date:   Fri, 21 May 2021 11:51:58 +0200
From:   Vitaly Kuznetsov <vkuznets@...hat.com>
To:     kvm@...r.kernel.org, Paolo Bonzini <pbonzini@...hat.com>
Cc:     Sean Christopherson <seanjc@...gle.com>,
        Wanpeng Li <wanpengli@...cent.com>,
        Jim Mattson <jmattson@...gle.com>,
        Siddharth Chandrasekaran <sidcha@...zon.de>,
        linux-kernel@...r.kernel.org
Subject: [PATCH v2 24/30] KVM: x86: hyper-v: Honor HV_DEBUGGING privilege bit

Hyper-V partition must possess 'HV_DEBUGGING' privilege to issue
HVCALL_POST_DEBUG_DATA/HVCALL_RETRIEVE_DEBUG_DATA/
HVCALL_RESET_DEBUG_SESSION hypercalls.

Note, when SynDBG is disabled hv_check_hypercall_access() returns
'true' (like for any other unknown hypercall) so the result will
be HV_STATUS_INVALID_HYPERCALL_CODE and not HV_STATUS_ACCESS_DENIED.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/hyperv.c | 9 +++++++++
 1 file changed, 9 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 523f63287636..36ec688cda4e 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2035,6 +2035,15 @@ static bool hv_check_hypercall_access(struct kvm_vcpu_hv *hv_vcpu, u16 code)
 		return hv_vcpu->cpuid_cache.features_ebx & HV_POST_MESSAGES;
 	case HVCALL_SIGNAL_EVENT:
 		return hv_vcpu->cpuid_cache.features_ebx & HV_SIGNAL_EVENTS;
+	case HVCALL_POST_DEBUG_DATA:
+	case HVCALL_RETRIEVE_DEBUG_DATA:
+	case HVCALL_RESET_DEBUG_SESSION:
+		/*
+		 * Return 'true' when SynDBG is disabled so the resulting code
+		 * will be HV_STATUS_INVALID_HYPERCALL_CODE.
+		 */
+		return !kvm_hv_is_syndbg_enabled(hv_vcpu->vcpu) ||
+			hv_vcpu->cpuid_cache.features_ebx & HV_DEBUGGING;
 	default:
 		break;
 	}
-- 
2.31.1