linux-kernel - [PATCH RFC 05/22] KVM: x86: hyper-v: Honor HV_MSR_HYPERCALL

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Message-Id: <20210413122630.975617-6-vkuznets@redhat.com>
Date:   Tue, 13 Apr 2021 14:26:13 +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 05/22] KVM: x86: hyper-v: Honor HV_MSR_HYPERCALL_AVAILABLE privilege bit

HV_X64_MSR_GUEST_OS_ID/HV_X64_MSR_HYPERCALL are only available to guest
when HV_MSR_HYPERCALL_AVAILABLE bit is exposed.

Signed-off-by: Vitaly Kuznetsov <vkuznets@...hat.com>
---
 arch/x86/kvm/hyperv.c | 17 +++++++++++++++++
 1 file changed, 17 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index efb3d69c98fd..7fdd9b9c50d6 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1198,9 +1198,14 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
 {
 	struct kvm *kvm = vcpu->kvm;
 	struct kvm_hv *hv = to_kvm_hv(kvm);
+	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
 
 	switch (msr) {
 	case HV_X64_MSR_GUEST_OS_ID:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_HYPERCALL_AVAILABLE)))
+			return 1;
+
 		hv->hv_guest_os_id = data;
 		/* setting guest os id to zero disables hypercall page */
 		if (!hv->hv_guest_os_id)
@@ -1211,6 +1216,10 @@ static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
 		int i = 0;
 		u64 addr;
 
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_HYPERCALL_AVAILABLE)))
+			return 1;
+
 		/* if guest os id is not set hypercall should remain disabled */
 		if (!hv->hv_guest_os_id)
 			break;
@@ -1444,9 +1453,17 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata,
 
 	switch (msr) {
 	case HV_X64_MSR_GUEST_OS_ID:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_HYPERCALL_AVAILABLE)))
+			return 1;
+
 		data = hv->hv_guest_os_id;
 		break;
 	case HV_X64_MSR_HYPERCALL:
+		if (unlikely(!host && !(hv_vcpu->cpuid_cache.features_eax &
+					HV_MSR_HYPERCALL_AVAILABLE)))
+			return 1;
+
 		data = hv->hv_hypercall;
 		break;
 	case HV_X64_MSR_TIME_REF_COUNT:
-- 
2.30.2