linux-kernel - [PATCH RFC 06/22] KVM: x86: hyper-v: Honor HV_MSR_VP_INDEX

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Message-Id: <20210413122630.975617-7-vkuznets@redhat.com>
Date:   Tue, 13 Apr 2021 14:26:14 +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 06/22] KVM: x86: hyper-v: Honor HV_MSR_VP_INDEX_AVAILABLE privilege bit

HV_X64_MSR_VP_INDEX is only available to guest when
HV_MSR_VP_INDEX_AVAILABLE bit is exposed.

Note, writing to HV_X64_MSR_VP_INDEX 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 7fdd9b9c50d6..07f1fc8575e5 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1514,6 +1514,10 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata,
 
 	switch (msr) {
 	case HV_X64_MSR_VP_INDEX:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_VP_INDEX_AVAILABLE)))
+			return 1;
+
 		data = hv_vcpu->vp_index;
 		break;
 	case HV_X64_MSR_EOI:
-- 
2.30.2