arch/s390/kernel/nmi.c - linux - Git at Google

 // SPDX-License-Identifier: GPL-2.0
 /*
  *   Machine check handler
  *
  *    Copyright IBM Corp. 2000, 2009
  *    Author(s): Ingo Adlung <adlung@de.ibm.com>,
  *		 Martin Schwidefsky <schwidefsky@de.ibm.com>,
  *		 Cornelia Huck <cornelia.huck@de.ibm.com>,
  */

 #include <linux/kernel_stat.h>
 #include <linux/init.h>
 #include <linux/errno.h>
 #include <linux/entry-common.h>
 #include <linux/hardirq.h>
 #include <linux/log2.h>
 #include <linux/kprobes.h>
 #include <linux/kmemleak.h>
 #include <linux/time.h>
 #include <linux/module.h>
 #include <linux/sched/signal.h>
 #include <linux/kvm_host.h>
 #include <linux/export.h>
 #include <asm/lowcore.h>
 #include <asm/ctlreg.h>
 #include <asm/fpu.h>
 #include <asm/smp.h>
 #include <asm/stp.h>
 #include <asm/cputime.h>
 #include <asm/nmi.h>
 #include <asm/crw.h>
 #include <asm/asm-offsets.h>
 #include <asm/pai.h>

 struct mcck_struct {
 	unsigned int kill_task : 1;
 	unsigned int channel_report : 1;
 	unsigned int warning : 1;
 	unsigned int stp_queue : 1;
 	unsigned long mcck_code;
 };

 static DEFINE_PER_CPU(struct mcck_struct, cpu_mcck);

 static inline int nmi_needs_mcesa(void)
 {
 	return cpu_has_vx() || MACHINE_HAS_GS;
 }

 /*
  * The initial machine check extended save area for the boot CPU.
  * It will be replaced on the boot CPU reinit with an allocated
  * structure. The structure is required for machine check happening
  * early in the boot process.
  */
 static struct mcesa boot_mcesa __aligned(MCESA_MAX_SIZE);

 void __init nmi_alloc_mcesa_early(u64 *mcesad)
 {
 	if (!nmi_needs_mcesa())
 		return;
 	*mcesad = __pa(&boot_mcesa);
 	if (MACHINE_HAS_GS)
 		*mcesad |= ilog2(MCESA_MAX_SIZE);
 }

 int nmi_alloc_mcesa(u64 *mcesad)
 {
 	unsigned long size;
 	void *origin;

 	*mcesad = 0;
 	if (!nmi_needs_mcesa())
 		return 0;
 	size = MACHINE_HAS_GS ? MCESA_MAX_SIZE : MCESA_MIN_SIZE;
 	origin = kmalloc(size, GFP_KERNEL);
 	if (!origin)
 		return -ENOMEM;
 	/* The pointer is stored with mcesa_bits ORed in */
 	kmemleak_not_leak(origin);
 	*mcesad = __pa(origin);
 	if (MACHINE_HAS_GS)
 		*mcesad |= ilog2(MCESA_MAX_SIZE);
 	return 0;
 }

 void nmi_free_mcesa(u64 *mcesad)
 {
 	if (!nmi_needs_mcesa())
 		return;
 	kfree(__va(*mcesad & MCESA_ORIGIN_MASK));
 }

 static __always_inline char *nmi_puts(char *dest, const char *src)
 {
 	while (*src)
 		*dest++ = *src++;
 	*dest = 0;
 	return dest;
 }

 static __always_inline char *u64_to_hex(char *dest, u64 val)
 {
 	int i, num;

 	for (i = 1; i <= 16; i++) {
 		num = (val >> (64 - 4 * i)) & 0xf;
 		if (num >= 10)
 			*dest++ = 'A' + num - 10;
 		else
 			*dest++ = '0' + num;
 	}
 	*dest = 0;
 	return dest;
 }

 static notrace void s390_handle_damage(void)
 {
 	union ctlreg0 cr0, cr0_new;
 	char message[100];
 	psw_t psw_save;
 	char *ptr;

 	smp_emergency_stop();
 	diag_amode31_ops.diag308_reset();
 	ptr = nmi_puts(message, "System stopped due to unrecoverable machine check, code: 0x");
 	u64_to_hex(ptr, S390_lowcore.mcck_interruption_code);

 	/*
 	 * Disable low address protection and make machine check new PSW a
 	 * disabled wait PSW. Any additional machine check cannot be handled.
 	 */
 	local_ctl_store(0, &cr0.reg);
 	cr0_new = cr0;
 	cr0_new.lap = 0;
 	local_ctl_load(0, &cr0_new.reg);
 	psw_save = S390_lowcore.mcck_new_psw;
 	psw_bits(S390_lowcore.mcck_new_psw).io = 0;
 	psw_bits(S390_lowcore.mcck_new_psw).ext = 0;
 	psw_bits(S390_lowcore.mcck_new_psw).wait = 1;
 	sclp_emergency_printk(message);

 	/*
 	 * Restore machine check new PSW and control register 0 to original
 	 * values. This makes possible system dump analysis easier.
 	 */
 	S390_lowcore.mcck_new_psw = psw_save;
 	local_ctl_load(0, &cr0.reg);
 	disabled_wait();
 	while (1);
 }
 NOKPROBE_SYMBOL(s390_handle_damage);

 /*
  * Main machine check handler function. Will be called with interrupts disabled
  * and machine checks enabled.
  */
 void s390_handle_mcck(void)
 {
 	struct mcck_struct mcck;
 	unsigned long mflags;

 	/*
 	 * Disable machine checks and get the current state of accumulated
 	 * machine checks. Afterwards delete the old state and enable machine
 	 * checks again.
 	 */
 	local_mcck_save(mflags);
 	mcck = *this_cpu_ptr(&cpu_mcck);
 	memset(this_cpu_ptr(&cpu_mcck), 0, sizeof(mcck));
 	local_mcck_restore(mflags);

 	if (mcck.channel_report)
 		crw_handle_channel_report();
 	/*
 	 * A warning may remain for a prolonged period on the bare iron.
 	 * (actually until the machine is powered off, or the problem is gone)
 	 * So we just stop listening for the WARNING MCH and avoid continuously
 	 * being interrupted.  One caveat is however, that we must do this per
 	 * processor and cannot use the smp version of ctl_clear_bit().
 	 * On VM we only get one interrupt per virtally presented machinecheck.
 	 * Though one suffices, we may get one interrupt per (virtual) cpu.
 	 */
 	if (mcck.warning) {	/* WARNING pending ? */
 		static int mchchk_wng_posted = 0;

 		/* Use single cpu clear, as we cannot handle smp here. */
 		local_ctl_clear_bit(14, CR14_WARNING_SUBMASK_BIT);
 		if (xchg(&mchchk_wng_posted, 1) == 0)
 			kill_cad_pid(SIGPWR, 1);
 	}
 	if (mcck.stp_queue)
 		stp_queue_work();
 	if (mcck.kill_task) {
 		printk(KERN_EMERG "mcck: Terminating task because of machine "
 		       "malfunction (code 0x%016lx).\n", mcck.mcck_code);
 		printk(KERN_EMERG "mcck: task: %s, pid: %d.\n",
 		       current->comm, current->pid);
 		if (is_global_init(current))
 			panic("mcck: Attempting to kill init!\n");
 		do_send_sig_info(SIGKILL, SEND_SIG_PRIV, current, PIDTYPE_PID);
 	}
 }

 /**
  * nmi_registers_valid - verify if registers are valid
  * @mci: machine check interruption code
  *
  * Inspect a machine check interruption code and verify if all required
  * registers are valid. For some registers the corresponding validity bit is
  * ignored and the registers are set to the expected value.
  * Returns true if all registers are valid, otherwise false.
  */
 static bool notrace nmi_registers_valid(union mci mci)
 {
 	union ctlreg2 cr2;

 	/*
 	 * The getcpu vdso syscall reads the CPU number from the programmable
 	 * field of the TOD clock. Disregard the TOD programmable register
 	 * validity bit and load the CPU number into the TOD programmable field
 	 * unconditionally.
 	 */
 	set_tod_programmable_field(raw_smp_processor_id());
 	/*
 	 * Set the clock comparator register to the next expected value.
 	 */
 	set_clock_comparator(S390_lowcore.clock_comparator);
 	if (!mci.gr || !mci.fp || !mci.fc)
 		return false;
 	/*
 	 * The vector validity must only be checked if not running a
 	 * KVM guest. For KVM guests the machine check is forwarded by
 	 * KVM and it is the responsibility of the guest to take
 	 * appropriate actions. The host vector or FPU values have been
 	 * saved by KVM and will be restored by KVM.
 	 */
 	if (!mci.vr && !test_cpu_flag(CIF_MCCK_GUEST))
 		return false;
 	if (!mci.ar)
 		return false;
 	/*
 	 * Two cases for guarded storage registers:
 	 * - machine check in kernel or userspace
 	 * - machine check while running SIE (KVM guest)
 	 * For kernel or userspace the userspace values of guarded storage
 	 * control can not be recreated, the process must be terminated.
 	 * For SIE the guest values of guarded storage can not be recreated.
 	 * This is either due to a bug or due to GS being disabled in the
 	 * guest. The guest will be notified by KVM code and the guests machine
 	 * check handling must take care of this. The host values are saved by
 	 * KVM and are not affected.
 	 */
 	cr2.reg = S390_lowcore.cregs_save_area[2];
 	if (cr2.gse && !mci.gs && !test_cpu_flag(CIF_MCCK_GUEST))
 		return false;
 	if (!mci.ms || !mci.pm || !mci.ia)
 		return false;
 	return true;
 }
 NOKPROBE_SYMBOL(nmi_registers_valid);

 /*
  * Backup the guest's machine check info to its description block
  */
 static void notrace s390_backup_mcck_info(struct pt_regs *regs)
 {
 	struct mcck_volatile_info *mcck_backup;
 	struct sie_page *sie_page;

 	/* r14 contains the sie block, which was set in sie64a */
 	struct kvm_s390_sie_block *sie_block = phys_to_virt(regs->gprs[14]);

 	if (sie_block == NULL)
 		/* Something's seriously wrong, stop system. */
 		s390_handle_damage();

 	sie_page = container_of(sie_block, struct sie_page, sie_block);
 	mcck_backup = &sie_page->mcck_info;
 	mcck_backup->mcic = S390_lowcore.mcck_interruption_code &
 				~(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE);
 	mcck_backup->ext_damage_code = S390_lowcore.external_damage_code;
 	mcck_backup->failing_storage_address
 			= S390_lowcore.failing_storage_address;
 }
 NOKPROBE_SYMBOL(s390_backup_mcck_info);

 #define MAX_IPD_COUNT	29
 #define MAX_IPD_TIME	(5 * 60 * USEC_PER_SEC) /* 5 minutes */

 #define ED_STP_ISLAND	6	/* External damage STP island check */
 #define ED_STP_SYNC	7	/* External damage STP sync check */

 #define MCCK_CODE_NO_GUEST	(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE)

 /*
  * machine check handler.
  */
 void 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;
 	irqentry_state_t irq_state;
 	union mci mci;
 	unsigned long mcck_dam_code;
 	int mcck_pending = 0;

 	irq_state = irqentry_nmi_enter(regs);

 	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 (!nmi_registers_valid(mci)) {
 		if (!user_mode(regs))
 			s390_handle_damage();
 		/*
 		 * 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;
 	}
 	/*
 	 * Reinject storage related machine checks into the guest if they
 	 * happen when the guest is running.
 	 */
 	if (!test_cpu_flag(CIF_MCCK_GUEST)) {
 		/* Storage error uncorrected */
 		if (mci.se)
 			s390_handle_damage();
 		/* Storage key-error uncorrected */
 		if (mci.ke)
 			s390_handle_damage();
 		/* Storage degradation */
 		if (mci.ds && mci.fa)
 			s390_handle_damage();
 	}
 	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 (mcck_pending)
 		schedule_mcck_handler();

 	irqentry_nmi_exit(regs, irq_state);
 }
 NOKPROBE_SYMBOL(s390_do_machine_check);

 static int __init machine_check_init(void)
 {
 	system_ctl_set_bit(14, CR14_EXTERNAL_DAMAGE_SUBMASK_BIT);
 	system_ctl_set_bit(14, CR14_RECOVERY_SUBMASK_BIT);
 	system_ctl_set_bit(14, CR14_WARNING_SUBMASK_BIT);
 	return 0;
 }
 early_initcall(machine_check_init);
	// SPDX-License-Identifier: GPL-2.0
	/*
	* Machine check handler
	*
	* Copyright IBM Corp. 2000, 2009
	* Author(s): Ingo Adlung <adlung@de.ibm.com>,
	* Martin Schwidefsky <schwidefsky@de.ibm.com>,
	* Cornelia Huck <cornelia.huck@de.ibm.com>,
	*/

	#include <linux/kernel_stat.h>
	#include <linux/init.h>
	#include <linux/errno.h>
	#include <linux/entry-common.h>
	#include <linux/hardirq.h>
	#include <linux/log2.h>
	#include <linux/kprobes.h>
	#include <linux/kmemleak.h>
	#include <linux/time.h>
	#include <linux/module.h>
	#include <linux/sched/signal.h>
	#include <linux/kvm_host.h>
	#include <linux/export.h>
	#include <asm/lowcore.h>
	#include <asm/ctlreg.h>
	#include <asm/fpu.h>
	#include <asm/smp.h>
	#include <asm/stp.h>
	#include <asm/cputime.h>
	#include <asm/nmi.h>
	#include <asm/crw.h>
	#include <asm/asm-offsets.h>
	#include <asm/pai.h>

	struct mcck_struct {
	unsigned int kill_task : 1;
	unsigned int channel_report : 1;
	unsigned int warning : 1;
	unsigned int stp_queue : 1;
	unsigned long mcck_code;
	};

	static DEFINE_PER_CPU(struct mcck_struct, cpu_mcck);

	static inline int nmi_needs_mcesa(void)
	{
	return cpu_has_vx() \|\| MACHINE_HAS_GS;
	}

	/*
	* The initial machine check extended save area for the boot CPU.
	* It will be replaced on the boot CPU reinit with an allocated
	* structure. The structure is required for machine check happening
	* early in the boot process.
	*/
	static struct mcesa boot_mcesa __aligned(MCESA_MAX_SIZE);

	void __init nmi_alloc_mcesa_early(u64 *mcesad)
	{
	if (!nmi_needs_mcesa())
	return;
	*mcesad = __pa(&boot_mcesa);
	if (MACHINE_HAS_GS)
	*mcesad \|= ilog2(MCESA_MAX_SIZE);
	}

	int nmi_alloc_mcesa(u64 *mcesad)
	{
	unsigned long size;
	void *origin;

	*mcesad = 0;
	if (!nmi_needs_mcesa())
	return 0;
	size = MACHINE_HAS_GS ? MCESA_MAX_SIZE : MCESA_MIN_SIZE;
	origin = kmalloc(size, GFP_KERNEL);
	if (!origin)
	return -ENOMEM;
	/* The pointer is stored with mcesa_bits ORed in */
	kmemleak_not_leak(origin);
	*mcesad = __pa(origin);
	if (MACHINE_HAS_GS)
	*mcesad \|= ilog2(MCESA_MAX_SIZE);
	return 0;
	}

	void nmi_free_mcesa(u64 *mcesad)
	{
	if (!nmi_needs_mcesa())
	return;
	kfree(__va(*mcesad & MCESA_ORIGIN_MASK));
	}

	static __always_inline char nmi_puts(char dest, const char *src)
	{
	while (*src)
	dest++ = src++;
	*dest = 0;
	return dest;
	}

	static __always_inline char u64_to_hex(char dest, u64 val)
	{
	int i, num;

	for (i = 1; i <= 16; i++) {
	num = (val >> (64 - 4 * i)) & 0xf;
	if (num >= 10)
	*dest++ = 'A' + num - 10;
	else
	*dest++ = '0' + num;
	}
	*dest = 0;
	return dest;
	}

	static notrace void s390_handle_damage(void)
	{
	union ctlreg0 cr0, cr0_new;
	char message[100];
	psw_t psw_save;
	char *ptr;

	smp_emergency_stop();
	diag_amode31_ops.diag308_reset();
	ptr = nmi_puts(message, "System stopped due to unrecoverable machine check, code: 0x");
	u64_to_hex(ptr, S390_lowcore.mcck_interruption_code);

	/*
	* Disable low address protection and make machine check new PSW a
	* disabled wait PSW. Any additional machine check cannot be handled.
	*/
	local_ctl_store(0, &cr0.reg);
	cr0_new = cr0;
	cr0_new.lap = 0;
	local_ctl_load(0, &cr0_new.reg);
	psw_save = S390_lowcore.mcck_new_psw;
	psw_bits(S390_lowcore.mcck_new_psw).io = 0;
	psw_bits(S390_lowcore.mcck_new_psw).ext = 0;
	psw_bits(S390_lowcore.mcck_new_psw).wait = 1;
	sclp_emergency_printk(message);

	/*
	* Restore machine check new PSW and control register 0 to original
	* values. This makes possible system dump analysis easier.
	*/
	S390_lowcore.mcck_new_psw = psw_save;
	local_ctl_load(0, &cr0.reg);
	disabled_wait();
	while (1);
	}
	NOKPROBE_SYMBOL(s390_handle_damage);

	/*
	* Main machine check handler function. Will be called with interrupts disabled
	* and machine checks enabled.
	*/
	void s390_handle_mcck(void)
	{
	struct mcck_struct mcck;
	unsigned long mflags;

	/*
	* Disable machine checks and get the current state of accumulated
	* machine checks. Afterwards delete the old state and enable machine
	* checks again.
	*/
	local_mcck_save(mflags);
	mcck = *this_cpu_ptr(&cpu_mcck);
	memset(this_cpu_ptr(&cpu_mcck), 0, sizeof(mcck));
	local_mcck_restore(mflags);

	if (mcck.channel_report)
	crw_handle_channel_report();
	/*
	* A warning may remain for a prolonged period on the bare iron.
	* (actually until the machine is powered off, or the problem is gone)
	* So we just stop listening for the WARNING MCH and avoid continuously
	* being interrupted. One caveat is however, that we must do this per
	* processor and cannot use the smp version of ctl_clear_bit().
	* On VM we only get one interrupt per virtally presented machinecheck.
	* Though one suffices, we may get one interrupt per (virtual) cpu.
	*/
	if (mcck.warning) { /* WARNING pending ? */
	static int mchchk_wng_posted = 0;

	/* Use single cpu clear, as we cannot handle smp here. */
	local_ctl_clear_bit(14, CR14_WARNING_SUBMASK_BIT);
	if (xchg(&mchchk_wng_posted, 1) == 0)
	kill_cad_pid(SIGPWR, 1);
	}
	if (mcck.stp_queue)
	stp_queue_work();
	if (mcck.kill_task) {
	printk(KERN_EMERG "mcck: Terminating task because of machine "
	"malfunction (code 0x%016lx).\n", mcck.mcck_code);
	printk(KERN_EMERG "mcck: task: %s, pid: %d.\n",
	current->comm, current->pid);
	if (is_global_init(current))
	panic("mcck: Attempting to kill init!\n");
	do_send_sig_info(SIGKILL, SEND_SIG_PRIV, current, PIDTYPE_PID);
	}
	}

	/**
	* nmi_registers_valid - verify if registers are valid
	* @mci: machine check interruption code
	*
	* Inspect a machine check interruption code and verify if all required
	* registers are valid. For some registers the corresponding validity bit is
	* ignored and the registers are set to the expected value.
	* Returns true if all registers are valid, otherwise false.
	*/
	static bool notrace nmi_registers_valid(union mci mci)
	{
	union ctlreg2 cr2;

	/*
	* The getcpu vdso syscall reads the CPU number from the programmable
	* field of the TOD clock. Disregard the TOD programmable register
	* validity bit and load the CPU number into the TOD programmable field
	* unconditionally.
	*/
	set_tod_programmable_field(raw_smp_processor_id());
	/*
	* Set the clock comparator register to the next expected value.
	*/
	set_clock_comparator(S390_lowcore.clock_comparator);
	if (!mci.gr \|\| !mci.fp \|\| !mci.fc)
	return false;
	/*
	* The vector validity must only be checked if not running a
	* KVM guest. For KVM guests the machine check is forwarded by
	* KVM and it is the responsibility of the guest to take
	* appropriate actions. The host vector or FPU values have been
	* saved by KVM and will be restored by KVM.
	*/
	if (!mci.vr && !test_cpu_flag(CIF_MCCK_GUEST))
	return false;
	if (!mci.ar)
	return false;
	/*
	* Two cases for guarded storage registers:
	* - machine check in kernel or userspace
	* - machine check while running SIE (KVM guest)
	* For kernel or userspace the userspace values of guarded storage
	* control can not be recreated, the process must be terminated.
	* For SIE the guest values of guarded storage can not be recreated.
	* This is either due to a bug or due to GS being disabled in the
	* guest. The guest will be notified by KVM code and the guests machine
	* check handling must take care of this. The host values are saved by
	* KVM and are not affected.
	*/
	cr2.reg = S390_lowcore.cregs_save_area[2];
	if (cr2.gse && !mci.gs && !test_cpu_flag(CIF_MCCK_GUEST))
	return false;
	if (!mci.ms \|\| !mci.pm \|\| !mci.ia)
	return false;
	return true;
	}
	NOKPROBE_SYMBOL(nmi_registers_valid);

	/*
	* Backup the guest's machine check info to its description block
	*/
	static void notrace s390_backup_mcck_info(struct pt_regs *regs)
	{
	struct mcck_volatile_info *mcck_backup;
	struct sie_page *sie_page;

	/* r14 contains the sie block, which was set in sie64a */
	struct kvm_s390_sie_block *sie_block = phys_to_virt(regs->gprs[14]);

	if (sie_block == NULL)
	/* Something's seriously wrong, stop system. */
	s390_handle_damage();

	sie_page = container_of(sie_block, struct sie_page, sie_block);
	mcck_backup = &sie_page->mcck_info;
	mcck_backup->mcic = S390_lowcore.mcck_interruption_code &
	~(MCCK_CODE_CP \| MCCK_CODE_EXT_DAMAGE);
	mcck_backup->ext_damage_code = S390_lowcore.external_damage_code;
	mcck_backup->failing_storage_address
	= S390_lowcore.failing_storage_address;
	}
	NOKPROBE_SYMBOL(s390_backup_mcck_info);

	#define MAX_IPD_COUNT 29
	#define MAX_IPD_TIME (5 * 60 * USEC_PER_SEC) /* 5 minutes */

	#define ED_STP_ISLAND 6 /* External damage STP island check */
	#define ED_STP_SYNC 7 /* External damage STP sync check */

	#define MCCK_CODE_NO_GUEST (MCCK_CODE_CP \| MCCK_CODE_EXT_DAMAGE)

	/*
	* machine check handler.
	*/
	void 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;
	irqentry_state_t irq_state;
	union mci mci;
	unsigned long mcck_dam_code;
	int mcck_pending = 0;

	irq_state = irqentry_nmi_enter(regs);

	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 (!nmi_registers_valid(mci)) {
	if (!user_mode(regs))
	s390_handle_damage();
	/*
	* 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;
	}
	/*
	* Reinject storage related machine checks into the guest if they
	* happen when the guest is running.
	*/
	if (!test_cpu_flag(CIF_MCCK_GUEST)) {
	/* Storage error uncorrected */
	if (mci.se)
	s390_handle_damage();
	/* Storage key-error uncorrected */
	if (mci.ke)
	s390_handle_damage();
	/* Storage degradation */
	if (mci.ds && mci.fa)
	s390_handle_damage();
	}
	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 (mcck_pending)
	schedule_mcck_handler();

	irqentry_nmi_exit(regs, irq_state);
	}
	NOKPROBE_SYMBOL(s390_do_machine_check);

	static int __init machine_check_init(void)
	{
	system_ctl_set_bit(14, CR14_EXTERNAL_DAMAGE_SUBMASK_BIT);
	system_ctl_set_bit(14, CR14_RECOVERY_SUBMASK_BIT);
	system_ctl_set_bit(14, CR14_WARNING_SUBMASK_BIT);
	return 0;
	}
	early_initcall(machine_check_init);