KVM: PPC: Tell guest about pending interrupts

When the guest turns on interrupts again, it needs to know if we have an
interrupt pending for it. Because if so, it should rather get out of guest
context and get the interrupt.

So we introduce a new field in the shared page that we use to tell the guest
that there's a pending interrupt lying around.
Signed-off-by: Alexander Graf <agraf@suse.de>
Signed-off-by: Avi Kivity <avi@redhat.com>

arch/powerpc/include/asm/kvm_para.h

@@ -37,6 +37,7 @@ struct kvm_vcpu_arch_shared {
 	__u64 dar;
 	__u64 msr;
 	__u32 dsisr;
+	__u32 int_pending;	/* Tells the guest if we have an interrupt */
 };
 
 #define KVM_SC_MAGIC_R0		0x4b564d21 /* "KVM!" */

arch/powerpc/kvm/book3s.c

@@ -337,6 +337,7 @@ int kvmppc_book3s_irqprio_deliver(struct kvm_vcpu *vcpu, unsigned int priority)
 void kvmppc_core_deliver_interrupts(struct kvm_vcpu *vcpu)
 {
 	unsigned long *pending = &vcpu->arch.pending_exceptions;
+	unsigned long old_pending = vcpu->arch.pending_exceptions;
 	unsigned int priority;
 
 #ifdef EXIT_DEBUG
@@ -356,6 +357,12 @@ void kvmppc_core_deliver_interrupts(struct kvm_vcpu *vcpu)
 					 BITS_PER_BYTE * sizeof(*pending),
 					 priority + 1);
 	}
+
+	/* Tell the guest about our interrupt status */
+	if (*pending)
+		vcpu->arch.shared->int_pending = 1;
+	else if (old_pending)
+		vcpu->arch.shared->int_pending = 0;
 }
 
 void kvmppc_set_pvr(struct kvm_vcpu *vcpu, u32 pvr)

arch/powerpc/kvm/booke.c

@@ -224,6 +224,7 @@ static int kvmppc_booke_irqprio_deliver(struct kvm_vcpu *vcpu,
 void kvmppc_core_deliver_interrupts(struct kvm_vcpu *vcpu)
 {
 	unsigned long *pending = &vcpu->arch.pending_exceptions;
+	unsigned long old_pending = vcpu->arch.pending_exceptions;
 	unsigned int priority;
 
 	priority = __ffs(*pending);
@@ -235,6 +236,12 @@ void kvmppc_core_deliver_interrupts(struct kvm_vcpu *vcpu)
 		                         BITS_PER_BYTE * sizeof(*pending),
 		                         priority + 1);
 	}
+
+	/* Tell the guest about our interrupt status */
+	if (*pending)
+		vcpu->arch.shared->int_pending = 1;
+	else if (old_pending)
+		vcpu->arch.shared->int_pending = 0;
 }
 
 /**