[PATCH 04/30] KVM: x86: hyper-v: Prepare to check access to Hyper-V MSRs

[Vitaly Kuznetsov]

Introduce hv_check_msr_access() to check if the particular MSR
should be accessible by guest, this will be used with
KVM_CAP_HYPERV_ENFORCE_CPUID mode.

No functional change intended.

Signed-off-by: Vitaly Kuznetsov <vkuznets@xxxxxxxxxx>
---
 arch/x86/kvm/hyperv.c | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index ccb298cfc933..b5bc16ea2595 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1193,12 +1193,21 @@ void kvm_hv_invalidate_tsc_page(struct kvm *kvm)
 	mutex_unlock(&hv->hv_lock);
 }
 
+
+static bool hv_check_msr_access(struct kvm_vcpu_hv *hv_vcpu, u32 msr)
+{
+	return true;
+}
+
 static int kvm_hv_set_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 data,
 			     bool host)
 {
 	struct kvm *kvm = vcpu->kvm;
 	struct kvm_hv *hv = to_kvm_hv(kvm);
 
+	if (unlikely(!host && !hv_check_msr_access(to_hv_vcpu(vcpu), msr)))
+		return 1;
+
 	switch (msr) {
 	case HV_X64_MSR_GUEST_OS_ID:
 		hv->hv_guest_os_id = data;
@@ -1327,6 +1336,9 @@ static int kvm_hv_set_msr(struct kvm_vcpu *vcpu, u32 msr, u64 data, bool host)
 {
 	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
 
+	if (unlikely(!host && !hv_check_msr_access(hv_vcpu, msr)))
+		return 1;
+
 	switch (msr) {
 	case HV_X64_MSR_VP_INDEX: {
 		struct kvm_hv *hv = to_kvm_hv(vcpu->kvm);
@@ -1441,6 +1453,9 @@ static int kvm_hv_get_msr_pw(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata,
 	struct kvm *kvm = vcpu->kvm;
 	struct kvm_hv *hv = to_kvm_hv(kvm);
 
+	if (unlikely(!host && !hv_check_msr_access(to_hv_vcpu(vcpu), msr)))
+		return 1;
+
 	switch (msr) {
 	case HV_X64_MSR_GUEST_OS_ID:
 		data = hv->hv_guest_os_id;
@@ -1490,6 +1505,9 @@ static int kvm_hv_get_msr(struct kvm_vcpu *vcpu, u32 msr, u64 *pdata,
 	u64 data = 0;
 	struct kvm_vcpu_hv *hv_vcpu = to_hv_vcpu(vcpu);
 
+	if (unlikely(!host && !hv_check_msr_access(hv_vcpu, msr)))
+		return 1;
+
 	switch (msr) {
 	case HV_X64_MSR_VP_INDEX:
 		data = hv_vcpu->vp_index;
-- 
2.30.2