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TOMOYO Linux Cross Reference
Linux/arch/s390/kvm/guestdbg.c

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  1 // SPDX-License-Identifier: GPL-2.0
  2 /*
  3  * kvm guest debug support
  4  *
  5  * Copyright IBM Corp. 2014
  6  *
  7  *    Author(s): David Hildenbrand <dahi@linux.vnet.ibm.com>
  8  */
  9 #include <linux/kvm_host.h>
 10 #include <linux/errno.h>
 11 #include "kvm-s390.h"
 12 #include "gaccess.h"
 13 
 14 /*
 15  * Extends the address range given by *start and *stop to include the address
 16  * range starting with estart and the length len. Takes care of overflowing
 17  * intervals and tries to minimize the overall interval size.
 18  */
 19 static void extend_address_range(u64 *start, u64 *stop, u64 estart, int len)
 20 {
 21         u64 estop;
 22 
 23         if (len > 0)
 24                 len--;
 25         else
 26                 len = 0;
 27 
 28         estop = estart + len;
 29 
 30         /* 0-0 range represents "not set" */
 31         if ((*start == 0) && (*stop == 0)) {
 32                 *start = estart;
 33                 *stop = estop;
 34         } else if (*start <= *stop) {
 35                 /* increase the existing range */
 36                 if (estart < *start)
 37                         *start = estart;
 38                 if (estop > *stop)
 39                         *stop = estop;
 40         } else {
 41                 /* "overflowing" interval, whereby *stop > *start */
 42                 if (estart <= *stop) {
 43                         if (estop > *stop)
 44                                 *stop = estop;
 45                 } else if (estop > *start) {
 46                         if (estart < *start)
 47                                 *start = estart;
 48                 }
 49                 /* minimize the range */
 50                 else if ((estop - *stop) < (*start - estart))
 51                         *stop = estop;
 52                 else
 53                         *start = estart;
 54         }
 55 }
 56 
 57 #define MAX_INST_SIZE 6
 58 
 59 static void enable_all_hw_bp(struct kvm_vcpu *vcpu)
 60 {
 61         unsigned long start, len;
 62         u64 *cr9 = &vcpu->arch.sie_block->gcr[9];
 63         u64 *cr10 = &vcpu->arch.sie_block->gcr[10];
 64         u64 *cr11 = &vcpu->arch.sie_block->gcr[11];
 65         int i;
 66 
 67         if (vcpu->arch.guestdbg.nr_hw_bp <= 0 ||
 68             vcpu->arch.guestdbg.hw_bp_info == NULL)
 69                 return;
 70 
 71         /*
 72          * If the guest is not interested in branching events, we can safely
 73          * limit them to the PER address range.
 74          */
 75         if (!(*cr9 & PER_EVENT_BRANCH))
 76                 *cr9 |= PER_CONTROL_BRANCH_ADDRESS;
 77         *cr9 |= PER_EVENT_IFETCH | PER_EVENT_BRANCH;
 78 
 79         for (i = 0; i < vcpu->arch.guestdbg.nr_hw_bp; i++) {
 80                 start = vcpu->arch.guestdbg.hw_bp_info[i].addr;
 81                 len = vcpu->arch.guestdbg.hw_bp_info[i].len;
 82 
 83                 /*
 84                  * The instruction in front of the desired bp has to
 85                  * report instruction-fetching events
 86                  */
 87                 if (start < MAX_INST_SIZE) {
 88                         len += start;
 89                         start = 0;
 90                 } else {
 91                         start -= MAX_INST_SIZE;
 92                         len += MAX_INST_SIZE;
 93                 }
 94 
 95                 extend_address_range(cr10, cr11, start, len);
 96         }
 97 }
 98 
 99 static void enable_all_hw_wp(struct kvm_vcpu *vcpu)
100 {
101         unsigned long start, len;
102         u64 *cr9 = &vcpu->arch.sie_block->gcr[9];
103         u64 *cr10 = &vcpu->arch.sie_block->gcr[10];
104         u64 *cr11 = &vcpu->arch.sie_block->gcr[11];
105         int i;
106 
107         if (vcpu->arch.guestdbg.nr_hw_wp <= 0 ||
108             vcpu->arch.guestdbg.hw_wp_info == NULL)
109                 return;
110 
111         /* if host uses storage alternation for special address
112          * spaces, enable all events and give all to the guest */
113         if (*cr9 & PER_EVENT_STORE && *cr9 & PER_CONTROL_ALTERATION) {
114                 *cr9 &= ~PER_CONTROL_ALTERATION;
115                 *cr10 = 0;
116                 *cr11 = -1UL;
117         } else {
118                 *cr9 &= ~PER_CONTROL_ALTERATION;
119                 *cr9 |= PER_EVENT_STORE;
120 
121                 for (i = 0; i < vcpu->arch.guestdbg.nr_hw_wp; i++) {
122                         start = vcpu->arch.guestdbg.hw_wp_info[i].addr;
123                         len = vcpu->arch.guestdbg.hw_wp_info[i].len;
124 
125                         extend_address_range(cr10, cr11, start, len);
126                 }
127         }
128 }
129 
130 void kvm_s390_backup_guest_per_regs(struct kvm_vcpu *vcpu)
131 {
132         vcpu->arch.guestdbg.cr0 = vcpu->arch.sie_block->gcr[0];
133         vcpu->arch.guestdbg.cr9 = vcpu->arch.sie_block->gcr[9];
134         vcpu->arch.guestdbg.cr10 = vcpu->arch.sie_block->gcr[10];
135         vcpu->arch.guestdbg.cr11 = vcpu->arch.sie_block->gcr[11];
136 }
137 
138 void kvm_s390_restore_guest_per_regs(struct kvm_vcpu *vcpu)
139 {
140         vcpu->arch.sie_block->gcr[0] = vcpu->arch.guestdbg.cr0;
141         vcpu->arch.sie_block->gcr[9] = vcpu->arch.guestdbg.cr9;
142         vcpu->arch.sie_block->gcr[10] = vcpu->arch.guestdbg.cr10;
143         vcpu->arch.sie_block->gcr[11] = vcpu->arch.guestdbg.cr11;
144 }
145 
146 void kvm_s390_patch_guest_per_regs(struct kvm_vcpu *vcpu)
147 {
148         /*
149          * TODO: if guest psw has per enabled, otherwise 0s!
150          * This reduces the amount of reported events.
151          * Need to intercept all psw changes!
152          */
153 
154         if (guestdbg_sstep_enabled(vcpu)) {
155                 /* disable timer (clock-comparator) interrupts */
156                 vcpu->arch.sie_block->gcr[0] &= ~CR0_CLOCK_COMPARATOR_SUBMASK;
157                 vcpu->arch.sie_block->gcr[9] |= PER_EVENT_IFETCH;
158                 vcpu->arch.sie_block->gcr[10] = 0;
159                 vcpu->arch.sie_block->gcr[11] = -1UL;
160         }
161 
162         if (guestdbg_hw_bp_enabled(vcpu)) {
163                 enable_all_hw_bp(vcpu);
164                 enable_all_hw_wp(vcpu);
165         }
166 
167         /* TODO: Instruction-fetching-nullification not allowed for now */
168         if (vcpu->arch.sie_block->gcr[9] & PER_EVENT_NULLIFICATION)
169                 vcpu->arch.sie_block->gcr[9] &= ~PER_EVENT_NULLIFICATION;
170 }
171 
172 #define MAX_WP_SIZE 100
173 
174 static int __import_wp_info(struct kvm_vcpu *vcpu,
175                             struct kvm_hw_breakpoint *bp_data,
176                             struct kvm_hw_wp_info_arch *wp_info)
177 {
178         int ret = 0;
179         wp_info->len = bp_data->len;
180         wp_info->addr = bp_data->addr;
181         wp_info->phys_addr = bp_data->phys_addr;
182         wp_info->old_data = NULL;
183 
184         if (wp_info->len < 0 || wp_info->len > MAX_WP_SIZE)
185                 return -EINVAL;
186 
187         wp_info->old_data = kmalloc(bp_data->len, GFP_KERNEL_ACCOUNT);
188         if (!wp_info->old_data)
189                 return -ENOMEM;
190         /* try to backup the original value */
191         ret = read_guest_abs(vcpu, wp_info->phys_addr, wp_info->old_data,
192                              wp_info->len);
193         if (ret) {
194                 kfree(wp_info->old_data);
195                 wp_info->old_data = NULL;
196         }
197 
198         return ret;
199 }
200 
201 #define MAX_BP_COUNT 50
202 
203 int kvm_s390_import_bp_data(struct kvm_vcpu *vcpu,
204                             struct kvm_guest_debug *dbg)
205 {
206         int ret = 0, nr_wp = 0, nr_bp = 0, i;
207         struct kvm_hw_breakpoint *bp_data = NULL;
208         struct kvm_hw_wp_info_arch *wp_info = NULL;
209         struct kvm_hw_bp_info_arch *bp_info = NULL;
210 
211         if (dbg->arch.nr_hw_bp <= 0 || !dbg->arch.hw_bp)
212                 return 0;
213         else if (dbg->arch.nr_hw_bp > MAX_BP_COUNT)
214                 return -EINVAL;
215 
216         bp_data = memdup_array_user(dbg->arch.hw_bp, dbg->arch.nr_hw_bp,
217                                     sizeof(*bp_data));
218         if (IS_ERR(bp_data))
219                 return PTR_ERR(bp_data);
220 
221         for (i = 0; i < dbg->arch.nr_hw_bp; i++) {
222                 switch (bp_data[i].type) {
223                 case KVM_HW_WP_WRITE:
224                         nr_wp++;
225                         break;
226                 case KVM_HW_BP:
227                         nr_bp++;
228                         break;
229                 default:
230                         break;
231                 }
232         }
233 
234         if (nr_wp > 0) {
235                 wp_info = kmalloc_array(nr_wp,
236                                         sizeof(*wp_info),
237                                         GFP_KERNEL_ACCOUNT);
238                 if (!wp_info) {
239                         ret = -ENOMEM;
240                         goto error;
241                 }
242         }
243         if (nr_bp > 0) {
244                 bp_info = kmalloc_array(nr_bp,
245                                         sizeof(*bp_info),
246                                         GFP_KERNEL_ACCOUNT);
247                 if (!bp_info) {
248                         ret = -ENOMEM;
249                         goto error;
250                 }
251         }
252 
253         for (nr_wp = 0, nr_bp = 0, i = 0; i < dbg->arch.nr_hw_bp; i++) {
254                 switch (bp_data[i].type) {
255                 case KVM_HW_WP_WRITE:
256                         ret = __import_wp_info(vcpu, &bp_data[i],
257                                                &wp_info[nr_wp]);
258                         if (ret)
259                                 goto error;
260                         nr_wp++;
261                         break;
262                 case KVM_HW_BP:
263                         bp_info[nr_bp].len = bp_data[i].len;
264                         bp_info[nr_bp].addr = bp_data[i].addr;
265                         nr_bp++;
266                         break;
267                 }
268         }
269 
270         vcpu->arch.guestdbg.nr_hw_bp = nr_bp;
271         vcpu->arch.guestdbg.hw_bp_info = bp_info;
272         vcpu->arch.guestdbg.nr_hw_wp = nr_wp;
273         vcpu->arch.guestdbg.hw_wp_info = wp_info;
274         return 0;
275 error:
276         kfree(bp_data);
277         kfree(wp_info);
278         kfree(bp_info);
279         return ret;
280 }
281 
282 void kvm_s390_clear_bp_data(struct kvm_vcpu *vcpu)
283 {
284         int i;
285         struct kvm_hw_wp_info_arch *hw_wp_info = NULL;
286 
287         for (i = 0; i < vcpu->arch.guestdbg.nr_hw_wp; i++) {
288                 hw_wp_info = &vcpu->arch.guestdbg.hw_wp_info[i];
289                 kfree(hw_wp_info->old_data);
290                 hw_wp_info->old_data = NULL;
291         }
292         kfree(vcpu->arch.guestdbg.hw_wp_info);
293         vcpu->arch.guestdbg.hw_wp_info = NULL;
294 
295         kfree(vcpu->arch.guestdbg.hw_bp_info);
296         vcpu->arch.guestdbg.hw_bp_info = NULL;
297 
298         vcpu->arch.guestdbg.nr_hw_wp = 0;
299         vcpu->arch.guestdbg.nr_hw_bp = 0;
300 }
301 
302 static inline int in_addr_range(u64 addr, u64 a, u64 b)
303 {
304         if (a <= b)
305                 return (addr >= a) && (addr <= b);
306         else
307                 /* "overflowing" interval */
308                 return (addr >= a) || (addr <= b);
309 }
310 
311 #define end_of_range(bp_info) (bp_info->addr + bp_info->len - 1)
312 
313 static struct kvm_hw_bp_info_arch *find_hw_bp(struct kvm_vcpu *vcpu,
314                                               unsigned long addr)
315 {
316         struct kvm_hw_bp_info_arch *bp_info = vcpu->arch.guestdbg.hw_bp_info;
317         int i;
318 
319         if (vcpu->arch.guestdbg.nr_hw_bp == 0)
320                 return NULL;
321 
322         for (i = 0; i < vcpu->arch.guestdbg.nr_hw_bp; i++) {
323                 /* addr is directly the start or in the range of a bp */
324                 if (addr == bp_info->addr)
325                         goto found;
326                 if (bp_info->len > 0 &&
327                     in_addr_range(addr, bp_info->addr, end_of_range(bp_info)))
328                         goto found;
329 
330                 bp_info++;
331         }
332 
333         return NULL;
334 found:
335         return bp_info;
336 }
337 
338 static struct kvm_hw_wp_info_arch *any_wp_changed(struct kvm_vcpu *vcpu)
339 {
340         int i;
341         struct kvm_hw_wp_info_arch *wp_info = NULL;
342         void *temp = NULL;
343 
344         if (vcpu->arch.guestdbg.nr_hw_wp == 0)
345                 return NULL;
346 
347         for (i = 0; i < vcpu->arch.guestdbg.nr_hw_wp; i++) {
348                 wp_info = &vcpu->arch.guestdbg.hw_wp_info[i];
349                 if (!wp_info || !wp_info->old_data || wp_info->len <= 0)
350                         continue;
351 
352                 temp = kmalloc(wp_info->len, GFP_KERNEL_ACCOUNT);
353                 if (!temp)
354                         continue;
355 
356                 /* refetch the wp data and compare it to the old value */
357                 if (!read_guest_abs(vcpu, wp_info->phys_addr, temp,
358                                     wp_info->len)) {
359                         if (memcmp(temp, wp_info->old_data, wp_info->len)) {
360                                 kfree(temp);
361                                 return wp_info;
362                         }
363                 }
364                 kfree(temp);
365                 temp = NULL;
366         }
367 
368         return NULL;
369 }
370 
371 void kvm_s390_prepare_debug_exit(struct kvm_vcpu *vcpu)
372 {
373         vcpu->run->exit_reason = KVM_EXIT_DEBUG;
374         vcpu->guest_debug &= ~KVM_GUESTDBG_EXIT_PENDING;
375 }
376 
377 #define PER_CODE_MASK           (PER_EVENT_MASK >> 24)
378 #define PER_CODE_BRANCH         (PER_EVENT_BRANCH >> 24)
379 #define PER_CODE_IFETCH         (PER_EVENT_IFETCH >> 24)
380 #define PER_CODE_STORE          (PER_EVENT_STORE >> 24)
381 #define PER_CODE_STORE_REAL     (PER_EVENT_STORE_REAL >> 24)
382 
383 #define per_bp_event(code) \
384                         (code & (PER_CODE_IFETCH | PER_CODE_BRANCH))
385 #define per_write_wp_event(code) \
386                         (code & (PER_CODE_STORE | PER_CODE_STORE_REAL))
387 
388 static int debug_exit_required(struct kvm_vcpu *vcpu, u8 perc,
389                                unsigned long peraddr)
390 {
391         struct kvm_debug_exit_arch *debug_exit = &vcpu->run->debug.arch;
392         struct kvm_hw_wp_info_arch *wp_info = NULL;
393         struct kvm_hw_bp_info_arch *bp_info = NULL;
394         unsigned long addr = vcpu->arch.sie_block->gpsw.addr;
395 
396         if (guestdbg_hw_bp_enabled(vcpu)) {
397                 if (per_write_wp_event(perc) &&
398                     vcpu->arch.guestdbg.nr_hw_wp > 0) {
399                         wp_info = any_wp_changed(vcpu);
400                         if (wp_info) {
401                                 debug_exit->addr = wp_info->addr;
402                                 debug_exit->type = KVM_HW_WP_WRITE;
403                                 goto exit_required;
404                         }
405                 }
406                 if (per_bp_event(perc) &&
407                          vcpu->arch.guestdbg.nr_hw_bp > 0) {
408                         bp_info = find_hw_bp(vcpu, addr);
409                         /* remove duplicate events if PC==PER address */
410                         if (bp_info && (addr != peraddr)) {
411                                 debug_exit->addr = addr;
412                                 debug_exit->type = KVM_HW_BP;
413                                 vcpu->arch.guestdbg.last_bp = addr;
414                                 goto exit_required;
415                         }
416                         /* breakpoint missed */
417                         bp_info = find_hw_bp(vcpu, peraddr);
418                         if (bp_info && vcpu->arch.guestdbg.last_bp != peraddr) {
419                                 debug_exit->addr = peraddr;
420                                 debug_exit->type = KVM_HW_BP;
421                                 goto exit_required;
422                         }
423                 }
424         }
425         if (guestdbg_sstep_enabled(vcpu) && per_bp_event(perc)) {
426                 debug_exit->addr = addr;
427                 debug_exit->type = KVM_SINGLESTEP;
428                 goto exit_required;
429         }
430 
431         return 0;
432 exit_required:
433         return 1;
434 }
435 
436 static int per_fetched_addr(struct kvm_vcpu *vcpu, unsigned long *addr)
437 {
438         u8 exec_ilen = 0;
439         u16 opcode[3];
440         int rc;
441 
442         if (vcpu->arch.sie_block->icptcode == ICPT_PROGI) {
443                 /* PER address references the fetched or the execute instr */
444                 *addr = vcpu->arch.sie_block->peraddr;
445                 /*
446                  * Manually detect if we have an EXECUTE instruction. As
447                  * instructions are always 2 byte aligned we can read the
448                  * first two bytes unconditionally
449                  */
450                 rc = read_guest_instr(vcpu, *addr, &opcode, 2);
451                 if (rc)
452                         return rc;
453                 if (opcode[0] >> 8 == 0x44)
454                         exec_ilen = 4;
455                 if ((opcode[0] & 0xff0f) == 0xc600)
456                         exec_ilen = 6;
457         } else {
458                 /* instr was suppressed, calculate the responsible instr */
459                 *addr = __rewind_psw(vcpu->arch.sie_block->gpsw,
460                                      kvm_s390_get_ilen(vcpu));
461                 if (vcpu->arch.sie_block->icptstatus & 0x01) {
462                         exec_ilen = (vcpu->arch.sie_block->icptstatus & 0x60) >> 4;
463                         if (!exec_ilen)
464                                 exec_ilen = 4;
465                 }
466         }
467 
468         if (exec_ilen) {
469                 /* read the complete EXECUTE instr to detect the fetched addr */
470                 rc = read_guest_instr(vcpu, *addr, &opcode, exec_ilen);
471                 if (rc)
472                         return rc;
473                 if (exec_ilen == 6) {
474                         /* EXECUTE RELATIVE LONG - RIL-b format */
475                         s32 rl = *((s32 *) (opcode + 1));
476 
477                         /* rl is a _signed_ 32 bit value specifying halfwords */
478                         *addr += (u64)(s64) rl * 2;
479                 } else {
480                         /* EXECUTE - RX-a format */
481                         u32 base = (opcode[1] & 0xf000) >> 12;
482                         u32 disp = opcode[1] & 0x0fff;
483                         u32 index = opcode[0] & 0x000f;
484 
485                         *addr = base ? vcpu->run->s.regs.gprs[base] : 0;
486                         *addr += index ? vcpu->run->s.regs.gprs[index] : 0;
487                         *addr += disp;
488                 }
489                 *addr = kvm_s390_logical_to_effective(vcpu, *addr);
490         }
491         return 0;
492 }
493 
494 #define guest_per_enabled(vcpu) \
495                              (vcpu->arch.sie_block->gpsw.mask & PSW_MASK_PER)
496 
497 int kvm_s390_handle_per_ifetch_icpt(struct kvm_vcpu *vcpu)
498 {
499         const u64 cr10 = vcpu->arch.sie_block->gcr[10];
500         const u64 cr11 = vcpu->arch.sie_block->gcr[11];
501         const u8 ilen = kvm_s390_get_ilen(vcpu);
502         struct kvm_s390_pgm_info pgm_info = {
503                 .code = PGM_PER,
504                 .per_code = PER_CODE_IFETCH,
505                 .per_address = __rewind_psw(vcpu->arch.sie_block->gpsw, ilen),
506         };
507         unsigned long fetched_addr;
508         int rc;
509 
510         /*
511          * The PSW points to the next instruction, therefore the intercepted
512          * instruction generated a PER i-fetch event. PER address therefore
513          * points at the previous PSW address (could be an EXECUTE function).
514          */
515         if (!guestdbg_enabled(vcpu))
516                 return kvm_s390_inject_prog_irq(vcpu, &pgm_info);
517 
518         if (debug_exit_required(vcpu, pgm_info.per_code, pgm_info.per_address))
519                 vcpu->guest_debug |= KVM_GUESTDBG_EXIT_PENDING;
520 
521         if (!guest_per_enabled(vcpu) ||
522             !(vcpu->arch.sie_block->gcr[9] & PER_EVENT_IFETCH))
523                 return 0;
524 
525         rc = per_fetched_addr(vcpu, &fetched_addr);
526         if (rc < 0)
527                 return rc;
528         if (rc)
529                 /* instruction-fetching exceptions */
530                 return kvm_s390_inject_program_int(vcpu, PGM_ADDRESSING);
531 
532         if (in_addr_range(fetched_addr, cr10, cr11))
533                 return kvm_s390_inject_prog_irq(vcpu, &pgm_info);
534         return 0;
535 }
536 
537 static int filter_guest_per_event(struct kvm_vcpu *vcpu)
538 {
539         const u8 perc = vcpu->arch.sie_block->perc;
540         u64 addr = vcpu->arch.sie_block->gpsw.addr;
541         u64 cr9 = vcpu->arch.sie_block->gcr[9];
542         u64 cr10 = vcpu->arch.sie_block->gcr[10];
543         u64 cr11 = vcpu->arch.sie_block->gcr[11];
544         /* filter all events, demanded by the guest */
545         u8 guest_perc = perc & (cr9 >> 24) & PER_CODE_MASK;
546         unsigned long fetched_addr;
547         int rc;
548 
549         if (!guest_per_enabled(vcpu))
550                 guest_perc = 0;
551 
552         /* filter "successful-branching" events */
553         if (guest_perc & PER_CODE_BRANCH &&
554             cr9 & PER_CONTROL_BRANCH_ADDRESS &&
555             !in_addr_range(addr, cr10, cr11))
556                 guest_perc &= ~PER_CODE_BRANCH;
557 
558         /* filter "instruction-fetching" events */
559         if (guest_perc & PER_CODE_IFETCH) {
560                 rc = per_fetched_addr(vcpu, &fetched_addr);
561                 if (rc < 0)
562                         return rc;
563                 /*
564                  * Don't inject an irq on exceptions. This would make handling
565                  * on icpt code 8 very complex (as PSW was already rewound).
566                  */
567                 if (rc || !in_addr_range(fetched_addr, cr10, cr11))
568                         guest_perc &= ~PER_CODE_IFETCH;
569         }
570 
571         /* All other PER events will be given to the guest */
572         /* TODO: Check altered address/address space */
573 
574         vcpu->arch.sie_block->perc = guest_perc;
575 
576         if (!guest_perc)
577                 vcpu->arch.sie_block->iprcc &= ~PGM_PER;
578         return 0;
579 }
580 
581 #define pssec(vcpu) (vcpu->arch.sie_block->gcr[1] & _ASCE_SPACE_SWITCH)
582 #define hssec(vcpu) (vcpu->arch.sie_block->gcr[13] & _ASCE_SPACE_SWITCH)
583 #define old_ssec(vcpu) ((vcpu->arch.sie_block->tecmc >> 31) & 0x1)
584 #define old_as_is_home(vcpu) !(vcpu->arch.sie_block->tecmc & 0xffff)
585 
586 int kvm_s390_handle_per_event(struct kvm_vcpu *vcpu)
587 {
588         int rc, new_as;
589 
590         if (debug_exit_required(vcpu, vcpu->arch.sie_block->perc,
591                                 vcpu->arch.sie_block->peraddr))
592                 vcpu->guest_debug |= KVM_GUESTDBG_EXIT_PENDING;
593 
594         rc = filter_guest_per_event(vcpu);
595         if (rc)
596                 return rc;
597 
598         /*
599          * Only RP, SAC, SACF, PT, PTI, PR, PC instructions can trigger
600          * a space-switch event. PER events enforce space-switch events
601          * for these instructions. So if no PER event for the guest is left,
602          * we might have to filter the space-switch element out, too.
603          */
604         if (vcpu->arch.sie_block->iprcc == PGM_SPACE_SWITCH) {
605                 vcpu->arch.sie_block->iprcc = 0;
606                 new_as = psw_bits(vcpu->arch.sie_block->gpsw).as;
607 
608                 /*
609                  * If the AS changed from / to home, we had RP, SAC or SACF
610                  * instruction. Check primary and home space-switch-event
611                  * controls. (theoretically home -> home produced no event)
612                  */
613                 if (((new_as == PSW_BITS_AS_HOME) ^ old_as_is_home(vcpu)) &&
614                     (pssec(vcpu) || hssec(vcpu)))
615                         vcpu->arch.sie_block->iprcc = PGM_SPACE_SWITCH;
616 
617                 /*
618                  * PT, PTI, PR, PC instruction operate on primary AS only. Check
619                  * if the primary-space-switch-event control was or got set.
620                  */
621                 if (new_as == PSW_BITS_AS_PRIMARY && !old_as_is_home(vcpu) &&
622                     (pssec(vcpu) || old_ssec(vcpu)))
623                         vcpu->arch.sie_block->iprcc = PGM_SPACE_SWITCH;
624         }
625         return 0;
626 }
627 

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