linux-kernel - [PATCH RFC 03/22] KVM: x86: hyper-v: Honor HV_MSR_VP_RUNTIME

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Message-Id: <20210413122630.975617-4-vkuznets@redhat.com>
Date:   Tue, 13 Apr 2021 14:26:11 +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 03/22] KVM: x86: hyper-v: Honor HV_MSR_VP_RUNTIME_AVAILABLE privilege bit

HV_X64_MSR_VP_RUNTIME is only available to guest when
HV_MSR_VP_RUNTIME_AVAILABLE bit is exposed.

Note, writing to HV_X64_MSR_VP_RUNTIME is only available from the host so
kvm_hv_set_msr() doesn't need an additional check.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/hyperv.c | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 781f9da9a418..b39445aabbc2 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1504,6 +1504,10 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata,
 		data = hv_vcpu->hv_vapic;
 		break;
 	case HV_X64_MSR_VP_RUNTIME:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_VP_RUNTIME_AVAILABLE)))
+			return 1;
+
 		data = current_task_runtime_100ns() + hv_vcpu->runtime_offset;
 		break;
 	case HV_X64_MSR_SCONTROL:
-- 
2.30.2