[PATCH nVMX 1/2] x86: Enforce NMI controls on vmentry of L2 guests

[Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>]

According to Intel SDM 26.2.1.1, the following rules should be enforced
on vmentry:

 *  If the "NMI exiting" VM-execution control is 0, "Virtual NMIs"
    VM-execution control must be 0.
 *  If the “virtual NMIs” VM-execution control is 0, the “NMI-window
    exiting” VM-execution control must be 0.

This patch enforces these rules when entering an L2 guest.

Signed-off-by: Krish Sadhukhan <krish.sadhukhan@xxxxxxxxxx>
Reviewed-by: Liran Alon <liran.alon@xxxxxxxxxx>
---
 arch/x86/kvm/vmx.c | 29 +++++++++++++++++++++++++++--
 1 file changed, 27 insertions(+), 2 deletions(-)

diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 8eba631..24b88db 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1366,6 +1366,16 @@ static inline bool nested_cpu_has_preemption_timer(struct vmcs12 *vmcs12)
 		PIN_BASED_VMX_PREEMPTION_TIMER;
 }
 
+static inline bool nested_cpu_has_nmi_exiting(struct vmcs12 *vmcs12)
+{
+	return vmcs12->pin_based_vm_exec_control & PIN_BASED_NMI_EXITING;
+}
+
+static inline bool nested_cpu_has_virtual_nmis(struct vmcs12 *vmcs12)
+{
+	return vmcs12->pin_based_vm_exec_control & PIN_BASED_VIRTUAL_NMIS;
+}
+
 static inline int nested_cpu_has_ept(struct vmcs12 *vmcs12)
 {
 	return nested_cpu_has2(vmcs12, SECONDARY_EXEC_ENABLE_EPT);
@@ -5667,8 +5677,7 @@ static bool nested_exit_intr_ack_set(struct kvm_vcpu *vcpu)
 
 static bool nested_exit_on_nmi(struct kvm_vcpu *vcpu)
 {
-	return get_vmcs12(vcpu)->pin_based_vm_exec_control &
-		PIN_BASED_NMI_EXITING;
+	return nested_cpu_has_nmi_exiting(get_vmcs12(vcpu));
 }
 
 static void enable_irq_window(struct kvm_vcpu *vcpu)
@@ -10752,6 +10761,19 @@ static int prepare_vmcs02(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12,
 	return 0;
 }
 
+static int nested_vmx_check_nmi_controls(struct vmcs12 *vmcs12)
+{
+	if (!nested_cpu_has_nmi_exiting(vmcs12) &&
+	    nested_cpu_has_virtual_nmis(vmcs12))
+		return -EINVAL;
+
+	if (!nested_cpu_has_virtual_nmis(vmcs12) &&
+	    nested_cpu_has(vmcs12, CPU_BASED_VIRTUAL_NMI_PENDING))
+		return -EINVAL;
+
+	return 0;
+}
+
 static int check_vmentry_prereqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 {
 	struct vcpu_vmx *vmx = to_vmx(vcpu);
@@ -10796,6 +10818,9 @@ static int check_vmentry_prereqs(struct kvm_vcpu *vcpu, struct vmcs12 *vmcs12)
 				vmx->nested.nested_vmx_entry_ctls_high))
 		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
 
+	if (nested_vmx_check_nmi_controls(vmcs12))
+		return VMXERR_ENTRY_INVALID_CONTROL_FIELD;
+
 	if (nested_cpu_has_vmfunc(vmcs12)) {
 		if (vmcs12->vm_function_control &
 		    ~vmx->nested.nested_vmx_vmfunc_controls)
-- 
2.9.5