KVM: Add kvm_inject_realmode_interrupt() wrapper

This adds a wrapper function kvm_inject_realmode_interrupt() around the
emulator function emulate_int_real() to allow real mode interrupt injection.

[avi: initialize operand and address sizes before emulating interrupts]
[avi: initialize rip for real mode interrupt injection]
[avi: clear interrupt pending flag after emulating interrupt injection]

Signed-off-by: Mohammed Gamal <m.gamal005@gmail.com>
Signed-off-by: Avi Kivity <avi@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/x86.c

@@ -4188,6 +4188,35 @@ static void init_emulate_ctxt(struct kvm_vcpu *vcpu)
 	memcpy(c->regs, vcpu->arch.regs, sizeof c->regs);
 }
 
+int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq)
+{
+	struct decode_cache *c = &vcpu->arch.emulate_ctxt.decode;
+	int ret;
+
+	init_emulate_ctxt(vcpu);
+
+	vcpu->arch.emulate_ctxt.decode.op_bytes = 2;
+	vcpu->arch.emulate_ctxt.decode.ad_bytes = 2;
+	vcpu->arch.emulate_ctxt.decode.eip = vcpu->arch.emulate_ctxt.eip;
+	ret = emulate_int_real(&vcpu->arch.emulate_ctxt, &emulate_ops, irq);
+
+	if (ret != X86EMUL_CONTINUE)
+		return EMULATE_FAIL;
+
+	vcpu->arch.emulate_ctxt.eip = c->eip;
+	memcpy(vcpu->arch.regs, c->regs, sizeof c->regs);
+	kvm_rip_write(vcpu, vcpu->arch.emulate_ctxt.eip);
+	kvm_x86_ops->set_rflags(vcpu, vcpu->arch.emulate_ctxt.eflags);
+
+	if (irq == NMI_VECTOR)
+		vcpu->arch.nmi_pending = false;
+	else
+		vcpu->arch.interrupt.pending = false;
+
+	return EMULATE_DONE;
+}
+EXPORT_SYMBOL_GPL(kvm_inject_realmode_interrupt);
+
 static int handle_emulation_failure(struct kvm_vcpu *vcpu)
 {
 	++vcpu->stat.insn_emulation_fail;

arch/x86/kvm/x86.h

@@ -72,6 +72,7 @@ static inline int is_paging(struct kvm_vcpu *vcpu)
 
 void kvm_before_handle_nmi(struct kvm_vcpu *vcpu);
 void kvm_after_handle_nmi(struct kvm_vcpu *vcpu);
+int kvm_inject_realmode_interrupt(struct kvm_vcpu *vcpu, int irq);
 
 void kvm_write_tsc(struct kvm_vcpu *vcpu, u64 data);