KVM: x86: IRET emulation does not clear NMI masking

The IRET instruction should clear NMI masking, but the current implementation
does not do so.

Signed-off-by: Nadav Amit <namit@cs.technion.ac.il>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/include/asm/kvm_emulate.h

@@ -208,6 +208,7 @@ struct x86_emulate_ops {
 
 	void (*get_cpuid)(struct x86_emulate_ctxt *ctxt,
 			  u32 *eax, u32 *ebx, u32 *ecx, u32 *edx);
+	void (*set_nmi_mask)(struct x86_emulate_ctxt *ctxt, bool masked);
 };
 
 typedef u32 __attribute__((vector_size(16))) sse128_t;

arch/x86/kvm/emulate.c

@@ -2047,6 +2047,7 @@ static int emulate_iret_real(struct x86_emulate_ctxt *ctxt)
 
 	ctxt->eflags &= ~EFLG_RESERVED_ZEROS_MASK; /* Clear reserved zeros */
 	ctxt->eflags |= EFLG_RESERVED_ONE_MASK;
+	ctxt->ops->set_nmi_mask(ctxt, false);
 
 	return rc;
 }

arch/x86/kvm/x86.c

@@ -4963,6 +4963,11 @@ static void emulator_write_gpr(struct x86_emulate_ctxt *ctxt, unsigned reg, ulon
 	kvm_register_write(emul_to_vcpu(ctxt), reg, val);
 }
 
+static void emulator_set_nmi_mask(struct x86_emulate_ctxt *ctxt, bool masked)
+{
+	kvm_x86_ops->set_nmi_mask(emul_to_vcpu(ctxt), masked);
+}
+
 static const struct x86_emulate_ops emulate_ops = {
 	.read_gpr            = emulator_read_gpr,
 	.write_gpr           = emulator_write_gpr,
@@ -4998,6 +5003,7 @@ static const struct x86_emulate_ops emulate_ops = {
 	.put_fpu             = emulator_put_fpu,
 	.intercept           = emulator_intercept,
 	.get_cpuid           = emulator_get_cpuid,
+	.set_nmi_mask        = emulator_set_nmi_mask,
 };
 
 static void toggle_interruptibility(struct kvm_vcpu *vcpu, u32 mask)