KVM: X86: Fix loss of pending INIT due to race

When SMP VM start, AP may lost INIT because of receiving INIT between
kvm_vcpu_ioctl_x86_get/set_vcpu_events.

       vcpu 0                             vcpu 1
                                   kvm_vcpu_ioctl_x86_get_vcpu_events
                                     events->smi.latched_init = 0
  send INIT to vcpu1
    set vcpu1's pending_events
                                   kvm_vcpu_ioctl_x86_set_vcpu_events
                                      if (events->smi.latched_init == 0)
                                        clear INIT in pending_events

This patch fixes it by just update SMM related flags if we are in SMM.

Thanks Peng Hao for the report and original commit message.
Reported-by: Peng Hao <peng.hao2@zte.com.cn>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Radim Krčmář <rkrcmar@redhat.com>
Signed-off-by: Wanpeng Li <wanpeng.li@hotmail.com>
Reviewed-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Radim Krčmář <rkrcmar@redhat.com>

arch/x86/kvm/x86.c

@@ -3159,6 +3159,8 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
 		kvm_set_hflags(vcpu, hflags);
 
 		vcpu->arch.smi_pending = events->smi.pending;
+
+		if (events->smi.smm) {
 			if (events->smi.smm_inside_nmi)
 				vcpu->arch.hflags |= HF_SMM_INSIDE_NMI_MASK;
 			else
@@ -3170,6 +3172,7 @@ static int kvm_vcpu_ioctl_x86_set_vcpu_events(struct kvm_vcpu *vcpu,
 					clear_bit(KVM_APIC_INIT, &vcpu->arch.apic->pending_events);
 			}
 		}
+	}
 
 	kvm_make_request(KVM_REQ_EVENT, vcpu);