KVM: x86: latch INITs while in system management mode

Do not process INITs immediately while in system management mode, keep
it instead in apic->pending_events.  Tell userspace if an INIT is
pending when they issue GET_VCPU_EVENTS, and similarly handle the
new field in SET_VCPU_EVENTS.

Note that the same treatment should be done while in VMX non-root mode.

Reviewed-by: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>

arch/x86/kvm/x86.c

@@ -5482,6 +5482,9 @@ static void kvm_smm_changed(struct kvm_vcpu *vcpu)
 		if (unlikely(vcpu->arch.smi_pending)) {
 			kvm_make_request(KVM_REQ_SMI, vcpu);
 			vcpu->arch.smi_pending = 0;
+		} else {
+			/* Process a latched INIT, if any.  */
+			kvm_make_request(KVM_REQ_EVENT, vcpu);
 		}
 	}
 }