linux-kernel - [PATCH RFC 11/22] KVM: x86: hyper-v: Honor HV_MSR_APIC_ACCESS

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Date:   Tue, 13 Apr 2021 14:26:19 +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 11/22] KVM: x86: hyper-v: Honor HV_MSR_APIC_ACCESS_AVAILABLE privilege bit

HV_X64_MSR_EOI, HV_X64_MSR_ICR, HV_X64_MSR_TPR, and
HV_X64_MSR_VP_ASSIST_PAGE  are only available to guest when
HV_MSR_APIC_ACCESS_AVAILABLE bit is exposed.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/hyperv.c | 32 ++++++++++++++++++++++++++++++++
 1 file changed, 32 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 032305ad5615..9c4454873e00 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1401,6 +1401,10 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
 		u64 gfn;
 		unsigned long addr;
 
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_APIC_ACCESS_AVAILABLE)))
+			return 1;
+
 		if (!(data & HV_X64_MSR_VP_ASSIST_PAGE_ENABLE)) {
 			hv_vcpu->hv_vapic = data;
 			if (kvm_lapic_enable_pv_eoi(vcpu, 0, 0))
@@ -1428,10 +1432,22 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
 		break;
 	}
 	case HV_X64_MSR_EOI:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_APIC_ACCESS_AVAILABLE)))
+			return 1;
+
 		return kvm_hv_vapic_msr_write(vcpu, APIC_EOI, data);
 	case HV_X64_MSR_ICR:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_APIC_ACCESS_AVAILABLE)))
+			return 1;
+
 		return kvm_hv_vapic_msr_write(vcpu, APIC_ICR, data);
 	case HV_X64_MSR_TPR:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_APIC_ACCESS_AVAILABLE)))
+			return 1;
+
 		return kvm_hv_vapic_msr_write(vcpu, APIC_TASKPRI, data);
 	case HV_X64_MSR_VP_RUNTIME:
 		if (!host)
@@ -1564,12 +1580,28 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata,
 		data = hv_vcpu->vp_index;
 		break;
 	case HV_X64_MSR_EOI:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_APIC_ACCESS_AVAILABLE)))
+			return 1;
+
 		return kvm_hv_vapic_msr_read(vcpu, APIC_EOI, pdata);
 	case HV_X64_MSR_ICR:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_APIC_ACCESS_AVAILABLE)))
+			return 1;
+
 		return kvm_hv_vapic_msr_read(vcpu, APIC_ICR, pdata);
 	case HV_X64_MSR_TPR:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_APIC_ACCESS_AVAILABLE)))
+			return 1;
+
 		return kvm_hv_vapic_msr_read(vcpu, APIC_TASKPRI, pdata);
 	case HV_X64_MSR_VP_ASSIST_PAGE:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_APIC_ACCESS_AVAILABLE)))
+			return 1;
+
 		data = hv_vcpu->hv_vapic;
 		break;
 	case HV_X64_MSR_VP_RUNTIME:
-- 
2.30.2