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/cpufeature.h>
13 #include <linux/init.h>
14 #include <linux/errno.h>
15 #include <linux/entry-common.h>
16 #include <linux/hardirq.h>
17 #include <linux/log2.h>
18 #include <linux/kprobes.h>
19 #include <linux/kmemleak.h>
20 #include <linux/time.h>
21 #include <linux/module.h>
22 #include <linux/sched/signal.h>
23 #include <linux/kvm_host.h>
24 #include <linux/export.h>
25 #include <asm/lowcore.h>
26 #include <asm/ctlreg.h>
27 #include <asm/fpu.h>
28 #include <asm/smp.h>
29 #include <asm/stp.h>
30 #include <asm/cputime.h>
31 #include <asm/nmi.h>
32 #include <asm/crw.h>
33 #include <asm/asm-offsets.h>
34 #include <asm/pai.h>
35 #include <asm/vtime.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
nmi_needs_mcesa(void)47 static inline int nmi_needs_mcesa(void)
48 {
49 return cpu_has_vx() || cpu_has_gs();
50 }
51
52 /*
53 * The initial machine check extended save area for the boot CPU.
54 * It will be replaced on the boot CPU reinit with an allocated
55 * structure. The structure is required for machine check happening
56 * early in the boot process.
57 */
58 static struct mcesa boot_mcesa __aligned(MCESA_MAX_SIZE);
59
nmi_alloc_mcesa_early(u64 * mcesad)60 void __init nmi_alloc_mcesa_early(u64 *mcesad)
61 {
62 if (!nmi_needs_mcesa())
63 return;
64 *mcesad = __pa(&boot_mcesa);
65 if (cpu_has_gs())
66 *mcesad |= ilog2(MCESA_MAX_SIZE);
67 }
68
nmi_alloc_mcesa(u64 * mcesad)69 int nmi_alloc_mcesa(u64 *mcesad)
70 {
71 unsigned long size;
72 void *origin;
73
74 *mcesad = 0;
75 if (!nmi_needs_mcesa())
76 return 0;
77 size = cpu_has_gs() ? MCESA_MAX_SIZE : MCESA_MIN_SIZE;
78 origin = kmalloc(size, GFP_KERNEL);
79 if (!origin)
80 return -ENOMEM;
81 /* The pointer is stored with mcesa_bits ORed in */
82 kmemleak_not_leak(origin);
83 *mcesad = __pa(origin);
84 if (cpu_has_gs())
85 *mcesad |= ilog2(MCESA_MAX_SIZE);
86 return 0;
87 }
88
nmi_free_mcesa(u64 * mcesad)89 void nmi_free_mcesa(u64 *mcesad)
90 {
91 if (!nmi_needs_mcesa())
92 return;
93 kfree(__va(*mcesad & MCESA_ORIGIN_MASK));
94 }
95
nmi_puts(char * dest,const char * src)96 static __always_inline char *nmi_puts(char *dest, const char *src)
97 {
98 while (*src)
99 *dest++ = *src++;
100 *dest = 0;
101 return dest;
102 }
103
u64_to_hex(char * dest,u64 val)104 static __always_inline char *u64_to_hex(char *dest, u64 val)
105 {
106 int i, num;
107
108 for (i = 1; i <= 16; i++) {
109 num = (val >> (64 - 4 * i)) & 0xf;
110 if (num >= 10)
111 *dest++ = 'A' + num - 10;
112 else
113 *dest++ = '0' + num;
114 }
115 *dest = 0;
116 return dest;
117 }
118
s390_handle_damage(void)119 static notrace void s390_handle_damage(void)
120 {
121 struct lowcore *lc = get_lowcore();
122 union ctlreg0 cr0, cr0_new;
123 char message[100];
124 psw_t psw_save;
125 char *ptr;
126
127 smp_emergency_stop();
128 diag_amode31_ops.diag308_reset();
129 ptr = nmi_puts(message, "System stopped due to unrecoverable machine check, code: 0x");
130 u64_to_hex(ptr, lc->mcck_interruption_code);
131
132 /*
133 * Disable low address protection and make machine check new PSW a
134 * disabled wait PSW. Any additional machine check cannot be handled.
135 */
136 local_ctl_store(0, &cr0.reg);
137 cr0_new = cr0;
138 cr0_new.lap = 0;
139 local_ctl_load(0, &cr0_new.reg);
140 psw_save = lc->mcck_new_psw;
141 psw_bits(lc->mcck_new_psw).io = 0;
142 psw_bits(lc->mcck_new_psw).ext = 0;
143 psw_bits(lc->mcck_new_psw).wait = 1;
144 sclp_emergency_printk(message);
145
146 /*
147 * Restore machine check new PSW and control register 0 to original
148 * values. This makes possible system dump analysis easier.
149 */
150 lc->mcck_new_psw = psw_save;
151 local_ctl_load(0, &cr0.reg);
152 disabled_wait();
153 while (1);
154 }
155 NOKPROBE_SYMBOL(s390_handle_damage);
156
157 /*
158 * Main machine check handler function. Will be called with interrupts disabled
159 * and machine checks enabled.
160 */
s390_handle_mcck(void)161 void s390_handle_mcck(void)
162 {
163 struct mcck_struct mcck;
164 unsigned long mflags;
165
166 /*
167 * Disable machine checks and get the current state of accumulated
168 * machine checks. Afterwards delete the old state and enable machine
169 * checks again.
170 */
171 local_mcck_save(mflags);
172 mcck = *this_cpu_ptr(&cpu_mcck);
173 memset(this_cpu_ptr(&cpu_mcck), 0, sizeof(mcck));
174 local_mcck_restore(mflags);
175
176 if (mcck.channel_report)
177 crw_handle_channel_report();
178 /*
179 * A warning may remain for a prolonged period on the bare iron.
180 * (actually until the machine is powered off, or the problem is gone)
181 * So we just stop listening for the WARNING MCH and avoid continuously
182 * being interrupted. One caveat is however, that we must do this per
183 * processor and cannot use the smp version of ctl_clear_bit().
184 * On VM we only get one interrupt per virtally presented machinecheck.
185 * Though one suffices, we may get one interrupt per (virtual) cpu.
186 */
187 if (mcck.warning) { /* WARNING pending ? */
188 static int mchchk_wng_posted = 0;
189
190 /* Use single cpu clear, as we cannot handle smp here. */
191 local_ctl_clear_bit(14, CR14_WARNING_SUBMASK_BIT);
192 if (xchg(&mchchk_wng_posted, 1) == 0)
193 kill_cad_pid(SIGPWR, 1);
194 }
195 if (mcck.stp_queue)
196 stp_queue_work();
197 if (mcck.kill_task) {
198 printk(KERN_EMERG "mcck: Terminating task because of machine "
199 "malfunction (code 0x%016lx).\n", mcck.mcck_code);
200 printk(KERN_EMERG "mcck: task: %s, pid: %d.\n",
201 current->comm, current->pid);
202 if (is_global_init(current))
203 panic("mcck: Attempting to kill init!\n");
204 do_send_sig_info(SIGKILL, SEND_SIG_PRIV, current, PIDTYPE_PID);
205 }
206 }
207
208 /**
209 * nmi_registers_valid - verify if registers are valid
210 * @mci: machine check interruption code
211 *
212 * Inspect a machine check interruption code and verify if all required
213 * registers are valid. For some registers the corresponding validity bit is
214 * ignored and the registers are set to the expected value.
215 * Returns true if all registers are valid, otherwise false.
216 */
nmi_registers_valid(union mci mci)217 static bool notrace nmi_registers_valid(union mci mci)
218 {
219 union ctlreg2 cr2;
220
221 /*
222 * The getcpu vdso syscall reads the CPU number from the programmable
223 * field of the TOD clock. Disregard the TOD programmable register
224 * validity bit and load the CPU number into the TOD programmable field
225 * unconditionally.
226 */
227 set_tod_programmable_field(raw_smp_processor_id());
228 /*
229 * Set the clock comparator register to the next expected value.
230 */
231 set_clock_comparator(get_lowcore()->clock_comparator);
232 if (!mci.gr || !mci.fp || !mci.fc)
233 return false;
234 /*
235 * The vector validity must only be checked if not running a
236 * KVM guest. For KVM guests the machine check is forwarded by
237 * KVM and it is the responsibility of the guest to take
238 * appropriate actions. The host vector or FPU values have been
239 * saved by KVM and will be restored by KVM.
240 */
241 if (!mci.vr && !test_cpu_flag(CIF_MCCK_GUEST))
242 return false;
243 if (!mci.ar)
244 return false;
245 /*
246 * Two cases for guarded storage registers:
247 * - machine check in kernel or userspace
248 * - machine check while running SIE (KVM guest)
249 * For kernel or userspace the userspace values of guarded storage
250 * control can not be recreated, the process must be terminated.
251 * For SIE the guest values of guarded storage can not be recreated.
252 * This is either due to a bug or due to GS being disabled in the
253 * guest. The guest will be notified by KVM code and the guests machine
254 * check handling must take care of this. The host values are saved by
255 * KVM and are not affected.
256 */
257 cr2.reg = get_lowcore()->cregs_save_area[2];
258 if (cr2.gse && !mci.gs && !test_cpu_flag(CIF_MCCK_GUEST))
259 return false;
260 if (!mci.ms || !mci.pm || !mci.ia)
261 return false;
262 return true;
263 }
264 NOKPROBE_SYMBOL(nmi_registers_valid);
265
266 /*
267 * Backup the guest's machine check info to its description block
268 */
s390_backup_mcck_info(struct pt_regs * regs)269 static void notrace s390_backup_mcck_info(struct pt_regs *regs)
270 {
271 struct mcck_volatile_info *mcck_backup;
272 struct sie_page *sie_page;
273
274 /* r14 contains the sie block, which was set in sie64a */
275 struct kvm_s390_sie_block *sie_block = phys_to_virt(regs->gprs[14]);
276
277 if (sie_block == NULL)
278 /* Something's seriously wrong, stop system. */
279 s390_handle_damage();
280
281 sie_page = container_of(sie_block, struct sie_page, sie_block);
282 mcck_backup = &sie_page->mcck_info;
283 mcck_backup->mcic = get_lowcore()->mcck_interruption_code &
284 ~(MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE);
285 mcck_backup->ext_damage_code = get_lowcore()->external_damage_code;
286 mcck_backup->failing_storage_address = get_lowcore()->failing_storage_address;
287 }
288 NOKPROBE_SYMBOL(s390_backup_mcck_info);
289
290 #define MAX_IPD_COUNT 29
291 #define MAX_IPD_TIME (5 * 60 * USEC_PER_SEC) /* 5 minutes */
292
293 #define ED_STP_ISLAND 6 /* External damage STP island check */
294 #define ED_STP_SYNC 7 /* External damage STP sync check */
295
296 #define MCCK_CODE_NO_GUEST (MCCK_CODE_CP | MCCK_CODE_EXT_DAMAGE)
297
298 /*
299 * machine check handler.
300 */
s390_do_machine_check(struct pt_regs * regs)301 void notrace s390_do_machine_check(struct pt_regs *regs)
302 {
303 static int ipd_count;
304 static DEFINE_SPINLOCK(ipd_lock);
305 static unsigned long long last_ipd;
306 struct lowcore *lc = get_lowcore();
307 struct mcck_struct *mcck;
308 unsigned long long tmp;
309 irqentry_state_t irq_state;
310 union mci mci;
311 unsigned long mcck_dam_code;
312 int mcck_pending = 0;
313
314 irq_state = irqentry_nmi_enter(regs);
315
316 if (user_mode(regs))
317 update_timer_mcck();
318 inc_irq_stat(NMI_NMI);
319 mci.val = lc->mcck_interruption_code;
320 mcck = this_cpu_ptr(&cpu_mcck);
321
322 /*
323 * Reinject the instruction processing damages' machine checks
324 * including Delayed Access Exception into the guest
325 * instead of damaging the host if they happen in the guest.
326 */
327 if (mci.pd && !test_cpu_flag(CIF_MCCK_GUEST)) {
328 if (mci.b) {
329 /* Processing backup -> verify if we can survive this */
330 u64 z_mcic, o_mcic, t_mcic;
331 z_mcic = (1ULL<<63 | 1ULL<<59 | 1ULL<<29);
332 o_mcic = (1ULL<<43 | 1ULL<<42 | 1ULL<<41 | 1ULL<<40 |
333 1ULL<<36 | 1ULL<<35 | 1ULL<<34 | 1ULL<<32 |
334 1ULL<<30 | 1ULL<<21 | 1ULL<<20 | 1ULL<<17 |
335 1ULL<<16);
336 t_mcic = mci.val;
337
338 if (((t_mcic & z_mcic) != 0) ||
339 ((t_mcic & o_mcic) != o_mcic)) {
340 s390_handle_damage();
341 }
342
343 /*
344 * Nullifying exigent condition, therefore we might
345 * retry this instruction.
346 */
347 spin_lock(&ipd_lock);
348 tmp = get_tod_clock();
349 if (((tmp - last_ipd) >> 12) < MAX_IPD_TIME)
350 ipd_count++;
351 else
352 ipd_count = 1;
353 last_ipd = tmp;
354 if (ipd_count == MAX_IPD_COUNT)
355 s390_handle_damage();
356 spin_unlock(&ipd_lock);
357 } else {
358 /* Processing damage -> stopping machine */
359 s390_handle_damage();
360 }
361 }
362 if (!nmi_registers_valid(mci)) {
363 if (!user_mode(regs))
364 s390_handle_damage();
365 /*
366 * Couldn't restore all register contents for the
367 * user space process -> mark task for termination.
368 */
369 mcck->kill_task = 1;
370 mcck->mcck_code = mci.val;
371 mcck_pending = 1;
372 }
373
374 /*
375 * Backup the machine check's info if it happens when the guest
376 * is running.
377 */
378 if (test_cpu_flag(CIF_MCCK_GUEST))
379 s390_backup_mcck_info(regs);
380
381 if (mci.cd) {
382 /* Timing facility damage */
383 s390_handle_damage();
384 }
385 if (mci.ed && mci.ec) {
386 /* External damage */
387 if (lc->external_damage_code & (1U << ED_STP_SYNC))
388 mcck->stp_queue |= stp_sync_check();
389 if (lc->external_damage_code & (1U << ED_STP_ISLAND))
390 mcck->stp_queue |= stp_island_check();
391 mcck_pending = 1;
392 }
393 /*
394 * Reinject storage related machine checks into the guest if they
395 * happen when the guest is running.
396 */
397 if (!test_cpu_flag(CIF_MCCK_GUEST)) {
398 /* Storage error uncorrected */
399 if (mci.se)
400 s390_handle_damage();
401 /* Storage key-error uncorrected */
402 if (mci.ke)
403 s390_handle_damage();
404 /* Storage degradation */
405 if (mci.ds && mci.fa)
406 s390_handle_damage();
407 }
408 if (mci.cp) {
409 /* Channel report word pending */
410 mcck->channel_report = 1;
411 mcck_pending = 1;
412 }
413 if (mci.w) {
414 /* Warning pending */
415 mcck->warning = 1;
416 mcck_pending = 1;
417 }
418
419 /*
420 * If there are only Channel Report Pending and External Damage
421 * machine checks, they will not be reinjected into the guest
422 * because they refer to host conditions only.
423 */
424 mcck_dam_code = (mci.val & MCIC_SUBCLASS_MASK);
425 if (test_cpu_flag(CIF_MCCK_GUEST) &&
426 (mcck_dam_code & MCCK_CODE_NO_GUEST) != mcck_dam_code) {
427 /* Set exit reason code for host's later handling */
428 *((long *)(regs->gprs[15] + __SF_SIE_REASON)) = -EINTR;
429 }
430 clear_cpu_flag(CIF_MCCK_GUEST);
431
432 if (mcck_pending)
433 schedule_mcck_handler();
434
435 irqentry_nmi_exit(regs, irq_state);
436 }
437 NOKPROBE_SYMBOL(s390_do_machine_check);
438
machine_check_init(void)439 static int __init machine_check_init(void)
440 {
441 system_ctl_set_bit(14, CR14_EXTERNAL_DAMAGE_SUBMASK_BIT);
442 system_ctl_set_bit(14, CR14_RECOVERY_SUBMASK_BIT);
443 system_ctl_set_bit(14, CR14_WARNING_SUBMASK_BIT);
444 return 0;
445 }
446 early_initcall(machine_check_init);
447