KVM: PPC: Allow userspace to unset the IRQ line

Userspace can tell us that it wants to trigger an interrupt. But
so far it can't tell us that it wants to stop triggering one.

So let's interpret the parameter to the ioctl that we have anyways
to tell us if we want to raise or lower the interrupt line.
Signed-off-by: Alexander Graf <agraf@suse.de>

v2 -> v3:

 - Add CAP for unset irq
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/powerpc/include/asm/kvm.h

@@ -84,4 +84,7 @@ struct kvm_guest_debug_arch {
 #define KVM_REG_QPR		0x0040
 #define KVM_REG_FQPR		0x0060
 
+#define KVM_INTERRUPT_SET	-1U
+#define KVM_INTERRUPT_UNSET	-2U
+
 #endif /* __LINUX_KVM_POWERPC_H */

arch/powerpc/include/asm/kvm_ppc.h

@@ -92,6 +92,8 @@ extern void kvmppc_core_queue_dec(struct kvm_vcpu *vcpu);
 extern void kvmppc_core_dequeue_dec(struct kvm_vcpu *vcpu);
 extern void kvmppc_core_queue_external(struct kvm_vcpu *vcpu,
                                        struct kvm_interrupt *irq);
+extern void kvmppc_core_dequeue_external(struct kvm_vcpu *vcpu,
+                                         struct kvm_interrupt *irq);
 
 extern int kvmppc_core_emulate_op(struct kvm_run *run, struct kvm_vcpu *vcpu,
                                   unsigned int op, int *advance);

arch/powerpc/kvm/book3s.c

@@ -231,6 +231,12 @@ void kvmppc_core_queue_external(struct kvm_vcpu *vcpu,
 	kvmppc_book3s_queue_irqprio(vcpu, BOOK3S_INTERRUPT_EXTERNAL);
 }
 
+void kvmppc_core_dequeue_external(struct kvm_vcpu *vcpu,
+                                  struct kvm_interrupt *irq)
+{
+	kvmppc_book3s_dequeue_irqprio(vcpu, BOOK3S_INTERRUPT_EXTERNAL);
+}
+
 int kvmppc_book3s_irqprio_deliver(struct kvm_vcpu *vcpu, unsigned int priority)
 {
 	int deliver = 1;

arch/powerpc/kvm/powerpc.c

@@ -149,6 +149,7 @@ int kvm_dev_ioctl_check_extension(long ext)
 	switch (ext) {
 	case KVM_CAP_PPC_SEGSTATE:
 	case KVM_CAP_PPC_PAIRED_SINGLES:
+	case KVM_CAP_PPC_UNSET_IRQ:
 		r = 1;
 		break;
 	case KVM_CAP_COALESCED_MMIO:
@@ -451,6 +452,9 @@ int kvm_arch_vcpu_ioctl_run(struct kvm_vcpu *vcpu, struct kvm_run *run)
 
 int kvm_vcpu_ioctl_interrupt(struct kvm_vcpu *vcpu, struct kvm_interrupt *irq)
 {
+	if (irq->irq == KVM_INTERRUPT_UNSET)
+		kvmppc_core_dequeue_external(vcpu, irq);
+	else
 		kvmppc_core_queue_external(vcpu, irq);
 
 	if (waitqueue_active(&vcpu->wq)) {

include/linux/kvm.h

@@ -507,6 +507,7 @@ struct kvm_ioeventfd {
 #define KVM_CAP_DEBUGREGS 50
 #endif
 #define KVM_CAP_X86_ROBUST_SINGLESTEP 51
+#define KVM_CAP_PPC_UNSET_IRQ 53
 
 #ifdef KVM_CAP_IRQ_ROUTING