linux-kernel - [PATCH RFC 08/22] KVM: x86: hyper-v: Honor HV_MSR_REFERENCE_TSC

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Message-Id: <20210413122630.975617-9-vkuznets@redhat.com>
Date:   Tue, 13 Apr 2021 14:26:16 +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, linux-hyperv@...r.kernel.org
Subject: [PATCH RFC 08/22] KVM: x86: hyper-v: Honor HV_MSR_REFERENCE_TSC_AVAILABLE privilege bit

HV_X64_MSR_REFERENCE_TSC is only available to guest when
HV_MSR_REFERENCE_TSC_AVAILABLE bit is exposed.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/hyperv.c | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 15d557ce32b5..48215ad72b6c 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1257,6 +1257,10 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
 		break;
 	}
 	case HV_X64_MSR_REFERENCE_TSC:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_REFERENCE_TSC_AVAILABLE)))
+			return 1;
+
 		hv->hv_tsc_page = data;
 		if (hv->hv_tsc_page & HV_X64_MSR_TSC_REFERENCE_ENABLE) {
 			if (!host)
@@ -1478,6 +1482,10 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata,
 		data = get_time_ref_counter(kvm);
 		break;
 	case HV_X64_MSR_REFERENCE_TSC:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_REFERENCE_TSC_AVAILABLE)))
+			return 1;
+
 		data = hv->hv_tsc_page;
 		break;
 	case HV_X64_MSR_CRASH_P0 ... HV_X64_MSR_CRASH_P4:
-- 
2.30.2