KVM: PPC: Book3S HV: Don't crash host on unknown guest interrupt

If we come out of a guest with an interrupt that we don't know about,
instead of crashing the host with a BUG(), we now return to userspace
with the exit reason set to KVM_EXIT_UNKNOWN and the trap vector in
the hw.hardware_exit_reason field of the kvm_run structure, as is done
on x86.  Note that run->exit_reason is already set to KVM_EXIT_UNKNOWN
at the beginning of kvmppc_handle_exit().
Signed-off-by: Paul Mackerras <paulus@samba.org>
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/kvm/book3s_hv.c

@@ -709,8 +709,8 @@ static int kvmppc_handle_exit(struct kvm_run *run, struct kvm_vcpu *vcpu,
 		printk(KERN_EMERG "trap=0x%x | pc=0x%lx | msr=0x%llx\n",
 			vcpu->arch.trap, kvmppc_get_pc(vcpu),
 			vcpu->arch.shregs.msr);
+		run->hw.hardware_exit_reason = vcpu->arch.trap;
 		r = RESUME_HOST;
-		BUG();
 		break;
 	}