KVM: x86: unify handling of interrupt window

The interrupt window is currently checked twice, once in vmx.c/svm.c and
once in dm_request_for_irq_injection.  The only difference is the extra
check for kvm_arch_interrupt_allowed in dm_request_for_irq_injection,
and the different return value (EINTR/KVM_EXIT_INTR for vmx.c/svm.c vs.
0/KVM_EXIT_IRQ_WINDOW_OPEN for dm_request_for_irq_injection).

However, dm_request_for_irq_injection is basically dead code!  Revive it
by removing the checks in vmx.c and svm.c's vmexit handlers, and
fixing the returned values for the dm_request_for_irq_injection case.
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/svm.c

@@ -3294,24 +3294,11 @@ static int msr_interception(struct vcpu_svm *svm)
 
 static int interrupt_window_interception(struct vcpu_svm *svm)
 {
-	struct kvm_run *kvm_run = svm->vcpu.run;
-
 	kvm_make_request(KVM_REQ_EVENT, &svm->vcpu);
 	svm_clear_vintr(svm);
 	svm->vmcb->control.int_ctl &= ~V_IRQ_MASK;
 	mark_dirty(svm->vmcb, VMCB_INTR);
 	++svm->vcpu.stat.irq_window_exits;
-	/*
-	 * If the user space waits to inject interrupts, exit as soon as
-	 * possible
-	 */
-	if (!lapic_in_kernel(&svm->vcpu) &&
-	    kvm_run->request_interrupt_window &&
-	    !kvm_cpu_has_interrupt(&svm->vcpu)) {
-		kvm_run->exit_reason = KVM_EXIT_IRQ_WINDOW_OPEN;
-		return 0;
-	}
-
 	return 1;
 }
 

arch/x86/kvm/vmx.c

@@ -5524,17 +5524,6 @@ static int handle_interrupt_window(struct kvm_vcpu *vcpu)
 	kvm_make_request(KVM_REQ_EVENT, vcpu);
 
 	++vcpu->stat.irq_window_exits;
-
-	/*
-	 * If the user space waits to inject interrupts, exit as soon as
-	 * possible
-	 */
-	if (!lapic_in_kernel(vcpu) &&
-	    vcpu->run->request_interrupt_window &&
-	    !kvm_cpu_has_interrupt(vcpu)) {
-		vcpu->run->exit_reason = KVM_EXIT_IRQ_WINDOW_OPEN;
-		return 0;
-	}
 	return 1;
 }
 

arch/x86/kvm/x86.c

@@ -6469,8 +6469,8 @@ static int vcpu_run(struct kvm_vcpu *vcpu)
 			kvm_inject_pending_timer_irqs(vcpu);
 
 		if (dm_request_for_irq_injection(vcpu)) {
-			r = -EINTR;
-			vcpu->run->exit_reason = KVM_EXIT_INTR;
+			r = 0;
+			vcpu->run->exit_reason = KVM_EXIT_IRQ_WINDOW_OPEN;
 			++vcpu->stat.request_irq_exits;
 			break;
 		}