linux-kernel - [PATCH RFC 12/22] KVM: x86: hyper-v: Honor HV_ACCESS_FREQUENCY

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Date:   Tue, 13 Apr 2021 14:26:20 +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 12/22] KVM: x86: hyper-v: Honor HV_ACCESS_FREQUENCY_MSRS privilege bit

HV_X64_MSR_TSC_FREQUENCY/HV_X64_MSR_APIC_FREQUENCY are only available to
guest when HV_ACCESS_FREQUENCY_MSRS bit is exposed.

Note, writing to HV_X64_MSR_TSC_FREQUENCY/HV_X64_MSR_APIC_FREQUENCY is
unsupported so kvm_hv_set_msr() doesn't need an additional check.

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 9c4454873e00..e92a1109ad9b 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1637,9 +1637,17 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata,
 					pdata, host);
 	}
 	case HV_X64_MSR_TSC_FREQUENCY:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_ACCESS_FREQUENCY_MSRS)))
+			return 1;
+
 		data = (u64)vcpu->arch.virtual_tsc_khz * 1000;
 		break;
 	case HV_X64_MSR_APIC_FREQUENCY:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_ACCESS_FREQUENCY_MSRS)))
+			return 1;
+
 		data = APIC_BUS_FREQUENCY;
 		break;
 	default:
-- 
2.30.2