linux-kernel - [PATCH v2 05/30] KVM: x86: hyper-v: Honor HV_MSR_HYPERCALL

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Date:   Fri, 21 May 2021 11:51:39 +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 05/30] KVM: x86: hyper-v: Honor HV_MSR_HYPERCALL_AVAILABLE privilege bit

HV_X64_MSR_GUEST_OS_ID/HV_X64_MSR_HYPERCALL are only available to guest
when HV_MSR_HYPERCALL_AVAILABLE bit is exposed.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/hyperv.c | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index b5bc16ea2595..13011803ebbd 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1196,6 +1196,18 @@ void kvm_hv_invalidate_tsc_page(struct kvm *kvm)
 
 static bool hv_check_msr_access(struct kvm_vcpu_hv *hv_vcpu, u32 msr)
 {
+	if (!hv_vcpu->enforce_cpuid)
+		return true;
+
+	switch (msr) {
+	case HV_X64_MSR_GUEST_OS_ID:
+	case HV_X64_MSR_HYPERCALL:
+		return hv_vcpu->cpuid_cache.features_eax &
+			HV_MSR_HYPERCALL_AVAILABLE;
+	default:
+		break;
+	}
+
 	return true;
 }
 
-- 
2.31.1