KVM: VMX: flush TLB with INVEPT on cpu migration

It is possible that stale EPTP-tagged mappings are used, if a
vcpu migrates to a different pcpu.

Set KVM_REQ_TLB_FLUSH in vmx_vcpu_load, when switching pcpus, which
will invalidate both VPID and EPT mappings on the next vm-entry.

Cc: stable@kernel.org
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

arch/x86/kvm/vmx.c

@@ -709,7 +709,7 @@ static void vmx_vcpu_load(struct kvm_vcpu *vcpu, int cpu)
 	if (vcpu->cpu != cpu) {
 		vcpu_clear(vmx);
 		kvm_migrate_timers(vcpu);
-		vpid_sync_vcpu_all(vmx);
+		set_bit(KVM_REQ_TLB_FLUSH, &vcpu->requests);
 		local_irq_disable();
 		list_add(&vmx->local_vcpus_link,
 			 &per_cpu(vcpus_on_cpu, cpu));