[PATCH v2 20/30] KVM: x86: hyper-v: Prepare to check access to Hyper-V hypercalls

[Vitaly Kuznetsov]

Introduce hv_check_hypercallr_access() to check if the particular hypercall
should be available to 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 | 11 +++++++++++
 1 file changed, 11 insertions(+)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 12b6803de1b7..4f0ab0c50c44 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -2022,6 +2022,11 @@ static u16 kvm_hvcall_signal_event(struct kvm_vcpu *vcpu, bool fast, u64 param)
 	return HV_STATUS_SUCCESS;
 }
 
+static bool hv_check_hypercall_access(struct kvm_vcpu_hv *hv_vcpu, u16 code)
+{
+	return true;
+}
+
 int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 {
 	u64 param, ingpa, outgpa, ret = HV_STATUS_SUCCESS;
@@ -2061,6 +2066,11 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 
 	trace_kvm_hv_hypercall(code, fast, rep_cnt, rep_idx, ingpa, outgpa);
 
+	if (unlikely(!hv_check_hypercall_access(to_hv_vcpu(vcpu), code))) {
+		ret = HV_STATUS_ACCESS_DENIED;
+		goto hypercall_complete;
+	}
+
 	switch (code) {
 	case HVCALL_NOTIFY_LONG_SPIN_WAIT:
 		if (unlikely(rep)) {
@@ -2167,6 +2177,7 @@ int kvm_hv_hypercall(struct kvm_vcpu *vcpu)
 		break;
 	}
 
+hypercall_complete:
 	return kvm_hv_hypercall_complete(vcpu, ret);
 }
 
-- 
2.31.1