int notrace s390_do_machine_check()

in kernel/nmi.c [373:496]

• 83 lines of code
• 23 McCabe index (conditional complexity)

int notrace s390_do_machine_check(struct pt_regs *regs)
{
	static int ipd_count;
	static DEFINE_SPINLOCK(ipd_lock);
	static unsigned long long last_ipd;
	struct mcck_struct *mcck;
	unsigned long long tmp;
	union mci mci;
	unsigned long mcck_dam_code;
	int mcck_pending = 0;

	nmi_enter();

	if (user_mode(regs))
		update_timer_mcck();
	inc_irq_stat(NMI_NMI);
	mci.val = S390_lowcore.mcck_interruption_code;
	mcck = this_cpu_ptr(&cpu_mcck);

	/*
	 * Reinject the instruction processing damages' machine checks
	 * including Delayed Access Exception into the guest
	 * instead of damaging the host if they happen in the guest.
	 */
	if (mci.pd && !test_cpu_flag(CIF_MCCK_GUEST)) {
		if (mci.b) {
			/* Processing backup -> verify if we can survive this */
			u64 z_mcic, o_mcic, t_mcic;
			z_mcic = (1ULL<<63 | 1ULL<<59 | 1ULL<<29);
			o_mcic = (1ULL<<43 | 1ULL<<42 | 1ULL<<41 | 1ULL<<40 |
				  1ULL<<36 | 1ULL<<35 | 1ULL<<34 | 1ULL<<32 |
				  1ULL<<30 | 1ULL<<21 | 1ULL<<20 | 1ULL<<17 |
				  1ULL<<16);
			t_mcic = mci.val;

			if (((t_mcic & z_mcic) != 0) ||
			    ((t_mcic & o_mcic) != o_mcic)) {
				s390_handle_damage();
			}

			/*
			 * Nullifying exigent condition, therefore we might
			 * retry this instruction.
			 */
			spin_lock(&ipd_lock);
			tmp = get_tod_clock();
			if (((tmp - last_ipd) >> 12) < MAX_IPD_TIME)
				ipd_count++;
			else
				ipd_count = 1;
			last_ipd = tmp;
			if (ipd_count == MAX_IPD_COUNT)
				s390_handle_damage();
			spin_unlock(&ipd_lock);
		} else {
			/* Processing damage -> stopping machine */
			s390_handle_damage();
		}
	}
	if (s390_validate_registers(mci, user_mode(regs))) {
		/*
		 * Couldn't restore all register contents for the
		 * user space process -> mark task for termination.
		 */
		mcck->kill_task = 1;
		mcck->mcck_code = mci.val;
		mcck_pending = 1;
	}

	/*
	 * Backup the machine check's info if it happens when the guest
	 * is running.
	 */
	if (test_cpu_flag(CIF_MCCK_GUEST))
		s390_backup_mcck_info(regs);

	if (mci.cd) {
		/* Timing facility damage */
		s390_handle_damage();
	}
	if (mci.ed && mci.ec) {
		/* External damage */
		if (S390_lowcore.external_damage_code & (1U << ED_STP_SYNC))
			mcck->stp_queue |= stp_sync_check();
		if (S390_lowcore.external_damage_code & (1U << ED_STP_ISLAND))
			mcck->stp_queue |= stp_island_check();
		mcck_pending = 1;
	}

	if (mci.cp) {
		/* Channel report word pending */
		mcck->channel_report = 1;
		mcck_pending = 1;
	}
	if (mci.w) {
		/* Warning pending */
		mcck->warning = 1;
		mcck_pending = 1;
	}

	/*
	 * If there are only Channel Report Pending and External Damage
	 * machine checks, they will not be reinjected into the guest
	 * because they refer to host conditions only.
	 */
	mcck_dam_code = (mci.val & MCIC_SUBCLASS_MASK);
	if (test_cpu_flag(CIF_MCCK_GUEST) &&
	(mcck_dam_code & MCCK_CODE_NO_GUEST) != mcck_dam_code) {
		/* Set exit reason code for host's later handling */
		*((long *)(regs->gprs[15] + __SF_SIE_REASON)) = -EINTR;
	}
	clear_cpu_flag(CIF_MCCK_GUEST);

	if (user_mode(regs) && mcck_pending) {
		nmi_exit();
		return 1;
	}

	if (mcck_pending)
		schedule_mcck_handler();

	nmi_exit();
	return 0;
}