KVM: PPC: Allow kvmppc_get_last_inst() to fail

On book3e, guest last instruction is read on the exit path using load
external pid (lwepx) dedicated instruction. This load operation may fail
due to TLB eviction and execute-but-not-read entries.

This patch lay down the path for an alternative solution to read the guest
last instruction, by allowing kvmppc_get_lat_inst() function to fail.
Architecture specific implmentations of kvmppc_load_last_inst() may read
last guest instruction and instruct the emulation layer to re-execute the
guest in case of failure.

Make kvmppc_get_last_inst() definition common between architectures.

Signed-off-by: Mihai Caraman <mihai.caraman@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/kvm/e500_mmu_host.c

@@ -610,6 +610,12 @@ void kvmppc_mmu_map(struct kvm_vcpu *vcpu, u64 eaddr, gpa_t gpaddr,
 	}
 }
 
+int kvmppc_load_last_inst(struct kvm_vcpu *vcpu, enum instruction_type type,
+			  u32 *instr)
+{
+	return EMULATE_AGAIN;
+}
+
 /************* MMU Notifiers *************/
 
 int kvm_unmap_hva(struct kvm *kvm, unsigned long hva)