1 // SPDX-License-Identifier: GPL-2.0
2 /*
3  *   Machine check handler
4  *
5  *    Copyright IBM Corp. 2000, 2009
6  *    Author(s): Ingo Adlung <adlung@de.ibm.com>,
7  *		 Martin Schwidefsky <schwidefsky@de.ibm.com>,
8  *		 Cornelia Huck <cornelia.huck@de.ibm.com>,
9  */
10 
11 #include <linux/kernel_stat.h>
12 #include <linux/init.h>
13 #include <linux/errno.h>
14 #include <linux/entry-common.h>
15 #include <linux/hardirq.h>
16 #include <linux/log2.h>
17 #include <linux/kprobes.h>
18 #include <linux/kmemleak.h>
19 #include <linux/time.h>
20 #include <linux/module.h>
21 #include <linux/sched/signal.h>
22 
23 #include <linux/export.h>
24 #include <asm/lowcore.h>
25 #include <asm/smp.h>
26 #include <asm/stp.h>
27 #include <asm/cputime.h>
28 #include <asm/nmi.h>
29 #include <asm/crw.h>
30 #include <asm/switch_to.h>
31 #include <asm/ctl_reg.h>
32 #include <asm/asm-offsets.h>
33 #include <asm/pai.h>
34 
35 #include <linux/kvm_host.h>
36 
37 struct mcck_struct {
38 	unsigned int kill_task : 1;
39 	unsigned int channel_report : 1;
40 	unsigned int warning : 1;
41 	unsigned int stp_queue : 1;
42 	unsigned long mcck_code;
43 };
44 
45 static DEFINE_PER_CPU(struct mcck_struct, cpu_mcck);
46 static struct kmem_cache *mcesa_cache;
47 static unsigned long mcesa_origin_lc;
48 
nmi_needs_mcesa(void)49 static inline int nmi_needs_mcesa(void)
50 {
51 	return MACHINE_HAS_VX || MACHINE_HAS_GS;
52 }
53 
nmi_get_mcesa_size(void)54 static inline unsigned long nmi_get_mcesa_size(void)
55 {
56 	if (MACHINE_HAS_GS)
57 		return MCESA_MAX_SIZE;
58 	return MCESA_MIN_SIZE;
59 }
60 
61 /*
62  * The initial machine check extended save area for the boot CPU.
63  * It will be replaced on the boot CPU reinit with an allocated
64  * structure. The structure is required for machine check happening
65  * early in the boot process.
66  */
67 static struct mcesa boot_mcesa __aligned(MCESA_MAX_SIZE);
68 
nmi_alloc_mcesa_early(u64 * mcesad)69 void __init nmi_alloc_mcesa_early(u64 *mcesad)
70 {
71 	if (!nmi_needs_mcesa())
72 		return;
73 	*mcesad = __pa(&boot_mcesa);
74 	if (MACHINE_HAS_GS)
75 		*mcesad |= ilog2(MCESA_MAX_SIZE);
76 }
77 
nmi_alloc_cache(void)78 static void __init nmi_alloc_cache(void)
79 {
80 	unsigned long size;
81 
82 	if (!nmi_needs_mcesa())
83 		return;
84 	size = nmi_get_mcesa_size();
85 	if (size > MCESA_MIN_SIZE)
86 		mcesa_origin_lc = ilog2(size);
87 	/* create slab cache for the machine-check-extended-save-areas */
88 	mcesa_cache = kmem_cache_create("nmi_save_areas", size, size, 0, NULL);
89 	if (!mcesa_cache)
90 		panic("Couldn't create nmi save area cache");
91 }
92 
nmi_alloc_mcesa(u64 * mcesad)93 int __ref nmi_alloc_mcesa(u64 *mcesad)
94 {
95 	unsigned long origin;
96 
97 	*mcesad = 0;
98 	if (!nmi_needs_mcesa())
99 		return 0;
100 	if (!mcesa_cache)
101 		nmi_alloc_cache();
102 	origin = (unsigned long) kmem_cache_alloc(mcesa_cache, GFP_KERNEL);
103 	if (!origin)
104 		return -ENOMEM;
105 	/* The pointer is stored with mcesa_bits ORed in */
106 	kmemleak_not_leak((void *) origin);
107 	*mcesad = __pa(origin) | mcesa_origin_lc;
108 	return 0;
109 }
110 
nmi_free_mcesa(u64 * mcesad)111 void nmi_free_mcesa(u64 *mcesad)
112 {
113 	if (!nmi_needs_mcesa())
114 		return;
115 	kmem_cache_free(mcesa_cache, __va(*mcesad & MCESA_ORIGIN_MASK));
116 }
117 
s390_handle_damage(void)118 static notrace void s390_handle_damage(void)
119 {
120 	smp_emergency_stop();
121 	disabled_wait();
122 	while (1);
123 }
124 NOKPROBE_SYMBOL(s390_handle_damage);
125 
126 /*
127  * Main machine check handler function. Will be called with interrupts disabled
128  * and machine checks enabled.
129  */
__s390_handle_mcck(void)130 void __s390_handle_mcck(void)
131 {
132 	struct mcck_struct mcck;
133 
134 	/*
135 	 * Disable machine checks and get the current state of accumulated
136 	 * machine checks. Afterwards delete the old state and enable machine
137 	 * checks again.
138 	 */
139 	local_mcck_disable();
140 	mcck = *this_cpu_ptr(&cpu_mcck);
141 	memset(this_cpu_ptr(&cpu_mcck), 0, sizeof(mcck));
142 	local_mcck_enable();
143 
144 	if (mcck.channel_report)
145 		crw_handle_channel_report();
146 	/*
147 	 * A warning may remain for a prolonged period on the bare iron.
148 	 * (actually until the machine is powered off, or the problem is gone)
149 	 * So we just stop listening for the WARNING MCH and avoid continuously
150 	 * being interrupted.  One caveat is however, that we must do this per
151 	 * processor and cannot use the smp version of ctl_clear_bit().
152 	 * On VM we only get one interrupt per virtally presented machinecheck.
153 	 * Though one suffices, we may get one interrupt per (virtual) cpu.
154 	 */
155 	if (mcck.warning) {	/* WARNING pending ? */
156 		static int mchchk_wng_posted = 0;
157 
158 		/* Use single cpu clear, as we cannot handle smp here. */
159 		__ctl_clear_bit(14, 24);	/* Disable WARNING MCH */
160 		if (xchg(&mchchk_wng_posted, 1) == 0)
161 			kill_cad_pid(SIGPWR, 1);
162 	}
163 	if (mcck.stp_queue)
164 		stp_queue_work();
165 	if (mcck.kill_task) {
166 		local_irq_enable();
167 		printk(KERN_EMERG "mcck: Terminating task because of machine "
168 		       "malfunction (code 0x%016lx).\n", mcck.mcck_code);
169 		printk(KERN_EMERG "mcck: task: %s, pid: %d.\n",
170 		       current->comm, current->pid);
171 		make_task_dead(SIGSEGV);
172 	}
173 }
174 
s390_handle_mcck(struct pt_regs * regs)175 void noinstr s390_handle_mcck(struct pt_regs *regs)
176 {
177 	trace_hardirqs_off();
178 	pai_kernel_enter(regs);
179 	__s390_handle_mcck();
180 	pai_kernel_exit(regs);
181 	trace_hardirqs_on();
182 }
183 /*
184  * returns 0 if all required registers are available
185  * returns 1 otherwise
186  */
s390_validate_registers(union mci mci,int umode)187 static int notrace s390_validate_registers(union mci mci, int umode)
188 {
189 	struct mcesa *mcesa;
190 	void *fpt_save_area;
191 	union ctlreg2 cr2;
192 	int kill_task;
193 	u64 zero;
194 
195 	kill_task = 0;
196 	zero = 0;
197 
198 	if (!mci.gr) {
199 		/*
200 		 * General purpose registers couldn't be restored and have
201 		 * unknown contents. Stop system or terminate process.
202 		 */
203 		if (!umode)
204 			s390_handle_damage();
205 		kill_task = 1;
206 	}
207 	if (!mci.fp) {
208 		/*
209 		 * Floating point registers can't be restored. If the
210 		 * kernel currently uses floating point registers the
211 		 * system is stopped. If the process has its floating
212 		 * pointer registers loaded it is terminated.
213 		 */
214 		if (S390_lowcore.fpu_flags & KERNEL_VXR_V0V7)
215 			s390_handle_damage();
216 		if (!test_cpu_flag(CIF_FPU))
217 			kill_task = 1;
218 	}
219 	fpt_save_area = &S390_lowcore.floating_pt_save_area;
220 	if (!mci.fc) {
221 		/*
222 		 * Floating point control register can't be restored.
223 		 * If the kernel currently uses the floating pointer
224 		 * registers and needs the FPC register the system is
225 		 * stopped. If the process has its floating pointer
226 		 * registers loaded it is terminated. Otherwise the
227 		 * FPC is just validated.
228 		 */
229 		if (S390_lowcore.fpu_flags & KERNEL_FPC)
230 			s390_handle_damage();
231 		asm volatile(
232 			"	lfpc	%0\n"
233 			:
234 			: "Q" (zero));
235 		if (!test_cpu_flag(CIF_FPU))
236 			kill_task = 1;
237 	} else {
238 		asm volatile(
239 			"	lfpc	%0\n"
240 			:
241 			: "Q" (S390_lowcore.fpt_creg_save_area));
242 	}
243 
244 	mcesa = __va(S390_lowcore.mcesad & MCESA_ORIGIN_MASK);
245 	if (!MACHINE_HAS_VX) {
246 		/* Validate floating point registers */
247 		asm volatile(
248 			"	ld	0,0(%0)\n"
249 			"	ld	1,8(%0)\n"
250 			"	ld	2,16(%0)\n"
251 			"	ld	3,24(%0)\n"
252 			"	ld	4,32(%0)\n"
253 			"	ld	5,40(%0)\n"
254 			"	ld	6,48(%0)\n"
255 			"	ld	7,56(%0)\n"
256 			"	ld	8,64(%0)\n"
257 			"	ld	9,72(%0)\n"
258 			"	ld	10,80(%0)\n"
259 			"	ld	11,88(%0)\n"
260 			"	ld	12,96(%0)\n"
261 			"	ld	13,104(%0)\n"
262 			"	ld	14,112(%0)\n"
263 			"	ld	15,120(%0)\n"
264 			:
265 			: "a" (fpt_save_area)
266 			: "memory");
267 	} else {
268 		/* Validate vector registers */
269 		union ctlreg0 cr0;
270 
271 		/*
272 		 * The vector validity must only be checked if not running a
273 		 * KVM guest. For KVM guests the machine check is forwarded by
274 		 * KVM and it is the responsibility of the guest to take
275 		 * appropriate actions. The host vector or FPU values have been
276 		 * saved by KVM and will be restored by KVM.
277 		 */
278 		if (!mci.vr && !test_cpu_flag(CIF_MCCK_GUEST)) {
279 			/*
280 			 * Vector registers can't be restored. If the kernel
281 			 * currently uses vector registers the system is
282 			 * stopped. If the process has its vector registers
283 			 * loaded it is terminated. Otherwise just validate
284 			 * the registers.
285 			 */
286 			if (S390_lowcore.fpu_flags & KERNEL_VXR)
287 				s390_handle_damage();
288 			if (!test_cpu_flag(CIF_FPU))
289 				kill_task = 1;
290 		}
291 		cr0.val = S390_lowcore.cregs_save_area[0];
292 		cr0.afp = cr0.vx = 1;
293 		__ctl_load(cr0.val, 0, 0);
294 		asm volatile(
295 			"	la	1,%0\n"
296 			"	.word	0xe70f,0x1000,0x0036\n" /* vlm 0,15,0(1) */
297 			"	.word	0xe70f,0x1100,0x0c36\n" /* vlm 16,31,256(1) */
298 			:
299 			: "Q" (*(struct vx_array *)mcesa->vector_save_area)
300 			: "1");
301 		__ctl_load(S390_lowcore.cregs_save_area[0], 0, 0);
302 	}
303 	/* Validate access registers */
304 	asm volatile(
305 		"	lam	0,15,0(%0)\n"
306 		:
307 		: "a" (&S390_lowcore.access_regs_save_area)
308 		: "memory");
309 	if (!mci.ar) {
310 		/*
311 		 * Access registers have unknown contents.
312 		 * Terminating task.
313 		 */
314 		kill_task = 1;
315 	}
316 	/* Validate guarded storage registers */
317 	cr2.val = S390_lowcore.cregs_save_area[2];
318 	if (cr2.gse) {
319 		if (!mci.gs) {
320 			/*
321 			 * 2 cases:
322 			 * - machine check in kernel or userspace
323 			 * - machine check while running SIE (KVM guest)
324 			 * For kernel or userspace the userspace values of
325 			 * guarded storage control can not be recreated, the
326 			 * process must be terminated.
327 			 * For SIE the guest values of guarded storage can not
328 			 * be recreated. This is either due to a bug or due to
329 			 * GS being disabled in the guest. The guest will be
330 			 * notified by KVM code and the guests machine check
331 			 * handling must take care of this.  The host values
332 			 * are saved by KVM and are not affected.
333 			 */
334 			if (!test_cpu_flag(CIF_MCCK_GUEST))
335 				kill_task = 1;
336 		} else {
337 			load_gs_cb((struct gs_cb *)mcesa->guarded_storage_save_area);
338 		}
339 	}
340 	/*
341 	 * The getcpu vdso syscall reads CPU number from the programmable
342 	 * field of the TOD clock. Disregard the TOD programmable register
343 	 * validity bit and load the CPU number into the TOD programmable
344 	 * field unconditionally.
345 	 */
346 	set_tod_programmable_field(raw_smp_processor_id());
347 	/* Validate clock comparator register */
348 	set_clock_comparator(S390_lowcore.clock_comparator);
349 
350 	if (!mci.ms || !mci.pm || !mci.ia)
351 		kill_task = 1;
352 
353 	return kill_task;
354 }
355 NOKPROBE_SYMBOL(s390_validate_registers);
356 
357 /*
358  * Backup the guest's machine check info to its description block
359  */
s390_backup_mcck_info(struct pt_regs * regs)360 static void notrace s390_backup_mcck_info(struct pt_regs *regs)
361 {
362 	struct mcck_volatile_info *mcck_backup;
363 	struct sie_page *sie_page;
364 
365 	/* r14 contains the sie block, which was set in sie64a */
366 	struct kvm_s390_sie_block *sie_block =
367 			(struct kvm_s390_sie_block *) regs->gprs[14];
368 
369 	if (sie_block == NULL)
370 		/* Something's seriously wrong, stop system. */
371 		s390_handle_damage();
372 
373 	sie_page = container_of(sie_block, struct sie_page, sie_block);
374 	mcck_backup = &sie_page->mcck_info;
375 	mcck_backup->mcic = S390_lowcore.mcck_interruption_code &
376 				~(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE);
377 	mcck_backup->ext_damage_code = S390_lowcore.external_damage_code;
378 	mcck_backup->failing_storage_address
379 			= S390_lowcore.failing_storage_address;
380 }
381 NOKPROBE_SYMBOL(s390_backup_mcck_info);
382 
383 #define MAX_IPD_COUNT	29
384 #define MAX_IPD_TIME	(5 * 60 * USEC_PER_SEC) /* 5 minutes */
385 
386 #define ED_STP_ISLAND	6	/* External damage STP island check */
387 #define ED_STP_SYNC	7	/* External damage STP sync check */
388 
389 #define MCCK_CODE_NO_GUEST	(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE)
390 
391 /*
392  * machine check handler.
393  */
s390_do_machine_check(struct pt_regs * regs)394 int notrace s390_do_machine_check(struct pt_regs *regs)
395 {
396 	static int ipd_count;
397 	static DEFINE_SPINLOCK(ipd_lock);
398 	static unsigned long long last_ipd;
399 	struct mcck_struct *mcck;
400 	unsigned long long tmp;
401 	irqentry_state_t irq_state;
402 	union mci mci;
403 	unsigned long mcck_dam_code;
404 	int mcck_pending = 0;
405 
406 	irq_state = irqentry_nmi_enter(regs);
407 
408 	if (user_mode(regs))
409 		update_timer_mcck();
410 	inc_irq_stat(NMI_NMI);
411 	mci.val = S390_lowcore.mcck_interruption_code;
412 	mcck = this_cpu_ptr(&cpu_mcck);
413 
414 	/*
415 	 * Reinject the instruction processing damages' machine checks
416 	 * including Delayed Access Exception into the guest
417 	 * instead of damaging the host if they happen in the guest.
418 	 */
419 	if (mci.pd && !test_cpu_flag(CIF_MCCK_GUEST)) {
420 		if (mci.b) {
421 			/* Processing backup -> verify if we can survive this */
422 			u64 z_mcic, o_mcic, t_mcic;
423 			z_mcic = (1ULL<<63 | 1ULL<<59 | 1ULL<<29);
424 			o_mcic = (1ULL<<43 | 1ULL<<42 | 1ULL<<41 | 1ULL<<40 |
425 				  1ULL<<36 | 1ULL<<35 | 1ULL<<34 | 1ULL<<32 |
426 				  1ULL<<30 | 1ULL<<21 | 1ULL<<20 | 1ULL<<17 |
427 				  1ULL<<16);
428 			t_mcic = mci.val;
429 
430 			if (((t_mcic & z_mcic) != 0) ||
431 			    ((t_mcic & o_mcic) != o_mcic)) {
432 				s390_handle_damage();
433 			}
434 
435 			/*
436 			 * Nullifying exigent condition, therefore we might
437 			 * retry this instruction.
438 			 */
439 			spin_lock(&ipd_lock);
440 			tmp = get_tod_clock();
441 			if (((tmp - last_ipd) >> 12) < MAX_IPD_TIME)
442 				ipd_count++;
443 			else
444 				ipd_count = 1;
445 			last_ipd = tmp;
446 			if (ipd_count == MAX_IPD_COUNT)
447 				s390_handle_damage();
448 			spin_unlock(&ipd_lock);
449 		} else {
450 			/* Processing damage -> stopping machine */
451 			s390_handle_damage();
452 		}
453 	}
454 	if (s390_validate_registers(mci, user_mode(regs))) {
455 		/*
456 		 * Couldn't restore all register contents for the
457 		 * user space process -> mark task for termination.
458 		 */
459 		mcck->kill_task = 1;
460 		mcck->mcck_code = mci.val;
461 		mcck_pending = 1;
462 	}
463 
464 	/*
465 	 * Backup the machine check's info if it happens when the guest
466 	 * is running.
467 	 */
468 	if (test_cpu_flag(CIF_MCCK_GUEST))
469 		s390_backup_mcck_info(regs);
470 
471 	if (mci.cd) {
472 		/* Timing facility damage */
473 		s390_handle_damage();
474 	}
475 	if (mci.ed && mci.ec) {
476 		/* External damage */
477 		if (S390_lowcore.external_damage_code & (1U << ED_STP_SYNC))
478 			mcck->stp_queue |= stp_sync_check();
479 		if (S390_lowcore.external_damage_code & (1U << ED_STP_ISLAND))
480 			mcck->stp_queue |= stp_island_check();
481 		mcck_pending = 1;
482 	}
483 
484 	if (mci.cp) {
485 		/* Channel report word pending */
486 		mcck->channel_report = 1;
487 		mcck_pending = 1;
488 	}
489 	if (mci.w) {
490 		/* Warning pending */
491 		mcck->warning = 1;
492 		mcck_pending = 1;
493 	}
494 
495 	/*
496 	 * If there are only Channel Report Pending and External Damage
497 	 * machine checks, they will not be reinjected into the guest
498 	 * because they refer to host conditions only.
499 	 */
500 	mcck_dam_code = (mci.val & MCIC_SUBCLASS_MASK);
501 	if (test_cpu_flag(CIF_MCCK_GUEST) &&
502 	(mcck_dam_code & MCCK_CODE_NO_GUEST) != mcck_dam_code) {
503 		/* Set exit reason code for host's later handling */
504 		*((long *)(regs->gprs[15] + __SF_SIE_REASON)) = -EINTR;
505 	}
506 	clear_cpu_flag(CIF_MCCK_GUEST);
507 
508 	if (user_mode(regs) && mcck_pending) {
509 		irqentry_nmi_exit(regs, irq_state);
510 		return 1;
511 	}
512 
513 	if (mcck_pending)
514 		schedule_mcck_handler();
515 
516 	irqentry_nmi_exit(regs, irq_state);
517 	return 0;
518 }
519 NOKPROBE_SYMBOL(s390_do_machine_check);
520 
machine_check_init(void)521 static int __init machine_check_init(void)
522 {
523 	ctl_set_bit(14, 25);	/* enable external damage MCH */
524 	ctl_set_bit(14, 27);	/* enable system recovery MCH */
525 	ctl_set_bit(14, 24);	/* enable warning MCH */
526 	return 0;
527 }
528 early_initcall(machine_check_init);
529