kvm/powerpc/e500mc: fix tlb invalidation on cpu migration

The existing check handles the case where we've migrated to a different
core than we last ran on, but it doesn't handle the case where we're
still on the same cpu we last ran on, but some other vcpu has run on
this cpu in the meantime.

Without this, guest segfaults (and other misbehavior) have been seen in
smp guests.

Cc: stable@vger.kernel.org # 3.8.x
Signed-off-by: Scott Wood <scottwood@freescale.com>
Signed-off-by: Alexander Graf <agraf@suse.de>

arch/powerpc/kvm/e500mc.c

@@ -108,6 +108,8 @@ void kvmppc_mmu_msr_notify(struct kvm_vcpu *vcpu, u32 old_msr)
 {
 }
 
+static DEFINE_PER_CPU(struct kvm_vcpu *, last_vcpu_on_cpu);
+
 void kvmppc_core_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 {
 	struct kvmppc_vcpu_e500 *vcpu_e500 = to_e500(vcpu);
@@ -136,8 +138,11 @@ void kvmppc_core_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	mtspr(SPRN_GDEAR, vcpu->arch.shared->dar);
 	mtspr(SPRN_GESR, vcpu->arch.shared->esr);
 
-	if (vcpu->arch.oldpir != mfspr(SPRN_PIR))
+	if (vcpu->arch.oldpir != mfspr(SPRN_PIR) ||
+	    __get_cpu_var(last_vcpu_on_cpu) != vcpu) {
 		kvmppc_e500_tlbil_all(vcpu_e500);
+		__get_cpu_var(last_vcpu_on_cpu) = vcpu;
+	}
 
 	kvmppc_load_guest_fp(vcpu);
 }