s390/kernel/vtime.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  *    Virtual cpu timer based timer functions.
   4  *
   5  *    Copyright IBM Corp. 2004, 2012
   6  *    Author(s): Jan Glauber <jan.glauber@de.ibm.com>
   7  */
   8
   9 #include <linux/kernel_stat.h>
  10 #include <linux/sched/cputime.h>
  11 #include <linux/export.h>
  12 #include <linux/kernel.h>
  13 #include <linux/timex.h>
  14 #include <linux/types.h>
  15 #include <linux/time.h>
  16 #include <asm/alternative.h>
  17 #include <asm/vtimer.h>
  18 #include <asm/vtime.h>
  19 #include <asm/cpu_mf.h>
  20 #include <asm/smp.h>
  21
  22 #include "entry.h"
  23
  24 static void virt_timer_expire(void);
  25
  26 static LIST_HEAD(virt_timer_list);
  27 static DEFINE_SPINLOCK(virt_timer_lock);
  28 static atomic64_t virt_timer_current;
  29 static atomic64_t virt_timer_elapsed;
  30
  31 DEFINE_PER_CPU(u64, mt_cycles[8]);
  32 static DEFINE_PER_CPU(u64, mt_scaling_mult) = { 1 };
  33 static DEFINE_PER_CPU(u64, mt_scaling_div) = { 1 };
  34 static DEFINE_PER_CPU(u64, mt_scaling_jiffies);
  35
  36 static inline u64 get_vtimer(void)
  37 {
  38         u64 timer;
  39
  40         asm volatile("stpt %0" : "=Q" (timer));
  41         return timer;
  42 }
  43
  44 static inline void set_vtimer(u64 expires)
  45 {
  46         u64 timer;
  47
  48         asm volatile(
  49                 "       stpt    %0\n"   /* Store current cpu timer value */
  50                 "       spt     %1"     /* Set new value imm. afterwards */
  51                 : "=Q" (timer) : "Q" (expires));
  52         S390_lowcore.system_timer += S390_lowcore.last_update_timer - timer;
  53         S390_lowcore.last_update_timer = expires;
  54 }
  55
  56 static inline int virt_timer_forward(u64 elapsed)
  57 {
  58         BUG_ON(!irqs_disabled());
  59
  60         if (list_empty(&virt_timer_list))
  61                 return 0;
  62         elapsed = atomic64_add_return(elapsed, &virt_timer_elapsed);
  63         return elapsed >= atomic64_read(&virt_timer_current);
  64 }
  65
  66 static void update_mt_scaling(void)
  67 {
  68         u64 cycles_new[8], *cycles_old;
  69         u64 delta, fac, mult, div;
  70         int i;
  71
  72         stcctm(MT_DIAG, smp_cpu_mtid + 1, cycles_new);
  73         cycles_old = this_cpu_ptr(mt_cycles);
  74         fac = 1;
  75         mult = div = 0;
  76         for (i = 0; i <= smp_cpu_mtid; i++) {
  77                 delta = cycles_new[i] - cycles_old[i];
  78                 div += delta;
  79                 mult *= i + 1;
  80                 mult += delta * fac;
  81                 fac *= i + 1;
  82         }
  83         div *= fac;
  84         if (div > 0) {
  85                 /* Update scaling factor */
  86                 __this_cpu_write(mt_scaling_mult, mult);
  87                 __this_cpu_write(mt_scaling_div, div);
  88                 memcpy(cycles_old, cycles_new,
  89                        sizeof(u64) * (smp_cpu_mtid + 1));
  90         }
  91         __this_cpu_write(mt_scaling_jiffies, jiffies_64);
  92 }
  93
  94 static inline u64 update_tsk_timer(unsigned long *tsk_vtime, u64 new)
  95 {
  96         u64 delta;
  97
  98         delta = new - *tsk_vtime;
  99         *tsk_vtime = new;
 100         return delta;
 101 }
 102
 103
 104 static inline u64 scale_vtime(u64 vtime)
 105 {
 106         u64 mult = __this_cpu_read(mt_scaling_mult);
 107         u64 div = __this_cpu_read(mt_scaling_div);
 108
 109         if (smp_cpu_mtid)
 110                 return vtime * mult / div;
 111         return vtime;
 112 }
 113
 114 static void account_system_index_scaled(struct task_struct *p, u64 cputime,
 115                                         enum cpu_usage_stat index)
 116 {
 117         p->stimescaled += cputime_to_nsecs(scale_vtime(cputime));
 118         account_system_index_time(p, cputime_to_nsecs(cputime), index);
 119 }
 120
 121 /*
 122  * Update process times based on virtual cpu times stored by entry.S
 123  * to the lowcore fields user_timer, system_timer & steal_clock.
 124  */
 125 static int do_account_vtime(struct task_struct *tsk)
 126 {
 127         u64 timer, clock, user, guest, system, hardirq, softirq;
 128
 129         timer = S390_lowcore.last_update_timer;
 130         clock = S390_lowcore.last_update_clock;
 131         asm volatile(
 132                 "       stpt    %0\n"   /* Store current cpu timer value */
 133                 "       stckf   %1"     /* Store current tod clock value */
 134                 : "=Q" (S390_lowcore.last_update_timer),
 135                   "=Q" (S390_lowcore.last_update_clock)
 136                 : : "cc");
 137         clock = S390_lowcore.last_update_clock - clock;
 138         timer -= S390_lowcore.last_update_timer;
 139
 140         if (hardirq_count())
 141                 S390_lowcore.hardirq_timer += timer;
 142         else
 143                 S390_lowcore.system_timer += timer;
 144
 145         /* Update MT utilization calculation */
 146         if (smp_cpu_mtid &&
 147             time_after64(jiffies_64, this_cpu_read(mt_scaling_jiffies)))
 148                 update_mt_scaling();
 149
 150         /* Calculate cputime delta */
 151         user = update_tsk_timer(&tsk->thread.user_timer,
 152                                 READ_ONCE(S390_lowcore.user_timer));
 153         guest = update_tsk_timer(&tsk->thread.guest_timer,
 154                                  READ_ONCE(S390_lowcore.guest_timer));
 155         system = update_tsk_timer(&tsk->thread.system_timer,
 156                                   READ_ONCE(S390_lowcore.system_timer));
 157         hardirq = update_tsk_timer(&tsk->thread.hardirq_timer,
 158                                    READ_ONCE(S390_lowcore.hardirq_timer));
 159         softirq = update_tsk_timer(&tsk->thread.softirq_timer,
 160                                    READ_ONCE(S390_lowcore.softirq_timer));
 161         S390_lowcore.steal_timer +=
 162                 clock - user - guest - system - hardirq - softirq;
 163
 164         /* Push account value */
 165         if (user) {
 166                 account_user_time(tsk, cputime_to_nsecs(user));
 167                 tsk->utimescaled += cputime_to_nsecs(scale_vtime(user));
 168         }
 169
 170         if (guest) {
 171                 account_guest_time(tsk, cputime_to_nsecs(guest));
 172                 tsk->utimescaled += cputime_to_nsecs(scale_vtime(guest));
 173         }
 174
 175         if (system)
 176                 account_system_index_scaled(tsk, system, CPUTIME_SYSTEM);
 177         if (hardirq)
 178                 account_system_index_scaled(tsk, hardirq, CPUTIME_IRQ);
 179         if (softirq)
 180                 account_system_index_scaled(tsk, softirq, CPUTIME_SOFTIRQ);
 181
 182         return virt_timer_forward(user + guest + system + hardirq + softirq);
 183 }
 184
 185 void vtime_task_switch(struct task_struct *prev)
 186 {
 187         do_account_vtime(prev);
 188         prev->thread.user_timer = S390_lowcore.user_timer;
 189         prev->thread.guest_timer = S390_lowcore.guest_timer;
 190         prev->thread.system_timer = S390_lowcore.system_timer;
 191         prev->thread.hardirq_timer = S390_lowcore.hardirq_timer;
 192         prev->thread.softirq_timer = S390_lowcore.softirq_timer;
 193         S390_lowcore.user_timer = current->thread.user_timer;
 194         S390_lowcore.guest_timer = current->thread.guest_timer;
 195         S390_lowcore.system_timer = current->thread.system_timer;
 196         S390_lowcore.hardirq_timer = current->thread.hardirq_timer;
 197         S390_lowcore.softirq_timer = current->thread.softirq_timer;
 198 }
 199
 200 /*
 201  * In s390, accounting pending user time also implies
 202  * accounting system time in order to correctly compute
 203  * the stolen time accounting.
 204  */
 205 void vtime_flush(struct task_struct *tsk)
 206 {
 207         u64 steal, avg_steal;
 208
 209         if (do_account_vtime(tsk))
 210                 virt_timer_expire();
 211
 212         steal = S390_lowcore.steal_timer;
 213         avg_steal = S390_lowcore.avg_steal_timer;
 214         if ((s64) steal > 0) {
 215                 S390_lowcore.steal_timer = 0;
 216                 account_steal_time(cputime_to_nsecs(steal));
 217                 avg_steal += steal;
 218         }
 219         S390_lowcore.avg_steal_timer = avg_steal / 2;
 220 }
 221
 222 static u64 vtime_delta(void)
 223 {
 224         u64 timer = S390_lowcore.last_update_timer;
 225
 226         S390_lowcore.last_update_timer = get_vtimer();
 227
 228         return timer - S390_lowcore.last_update_timer;
 229 }
 230
 231 /*
 232  * Update process times based on virtual cpu times stored by entry.S
 233  * to the lowcore fields user_timer, system_timer & steal_clock.
 234  */
 235 void vtime_account_kernel(struct task_struct *tsk)
 236 {
 237         u64 delta = vtime_delta();
 238
 239         if (tsk->flags & PF_VCPU)
 240                 S390_lowcore.guest_timer += delta;
 241         else
 242                 S390_lowcore.system_timer += delta;
 243
 244         virt_timer_forward(delta);
 245 }
 246 EXPORT_SYMBOL_GPL(vtime_account_kernel);
 247
 248 void vtime_account_softirq(struct task_struct *tsk)
 249 {
 250         u64 delta = vtime_delta();
 251
 252         S390_lowcore.softirq_timer += delta;
 253
 254         virt_timer_forward(delta);
 255 }
 256
 257 void vtime_account_hardirq(struct task_struct *tsk)
 258 {
 259         u64 delta = vtime_delta();
 260
 261         S390_lowcore.hardirq_timer += delta;
 262
 263         virt_timer_forward(delta);
 264 }
 265
 266 /*
 267  * Sorted add to a list. List is linear searched until first bigger
 268  * element is found.
 269  */
 270 static void list_add_sorted(struct vtimer_list *timer, struct list_head *head)
 271 {
 272         struct vtimer_list *tmp;
 273
 274         list_for_each_entry(tmp, head, entry) {
 275                 if (tmp->expires > timer->expires) {
 276                         list_add_tail(&timer->entry, &tmp->entry);
 277                         return;
 278                 }
 279         }
 280         list_add_tail(&timer->entry, head);
 281 }
 282
 283 /*
 284  * Handler for expired virtual CPU timer.
 285  */
 286 static void virt_timer_expire(void)
 287 {
 288         struct vtimer_list *timer, *tmp;
 289         unsigned long elapsed;
 290         LIST_HEAD(cb_list);
 291
 292         /* walk timer list, fire all expired timers */
 293         spin_lock(&virt_timer_lock);
 294         elapsed = atomic64_read(&virt_timer_elapsed);
 295         list_for_each_entry_safe(timer, tmp, &virt_timer_list, entry) {
 296                 if (timer->expires < elapsed)
 297                         /* move expired timer to the callback queue */
 298                         list_move_tail(&timer->entry, &cb_list);
 299                 else
 300                         timer->expires -= elapsed;
 301         }
 302         if (!list_empty(&virt_timer_list)) {
 303                 timer = list_first_entry(&virt_timer_list,
 304                                          struct vtimer_list, entry);
 305                 atomic64_set(&virt_timer_current, timer->expires);
 306         }
 307         atomic64_sub(elapsed, &virt_timer_elapsed);
 308         spin_unlock(&virt_timer_lock);
 309
 310         /* Do callbacks and recharge periodic timers */
 311         list_for_each_entry_safe(timer, tmp, &cb_list, entry) {
 312                 list_del_init(&timer->entry);
 313                 timer->function(timer->data);
 314                 if (timer->interval) {
 315                         /* Recharge interval timer */
 316                         timer->expires = timer->interval +
 317                                 atomic64_read(&virt_timer_elapsed);
 318                         spin_lock(&virt_timer_lock);
 319                         list_add_sorted(timer, &virt_timer_list);
 320                         spin_unlock(&virt_timer_lock);
 321                 }
 322         }
 323 }
 324
 325 void init_virt_timer(struct vtimer_list *timer)
 326 {
 327         timer->function = NULL;
 328         INIT_LIST_HEAD(&timer->entry);
 329 }
 330 EXPORT_SYMBOL(init_virt_timer);
 331
 332 static inline int vtimer_pending(struct vtimer_list *timer)
 333 {
 334         return !list_empty(&timer->entry);
 335 }
 336
 337 static void internal_add_vtimer(struct vtimer_list *timer)
 338 {
 339         if (list_empty(&virt_timer_list)) {
 340                 /* First timer, just program it. */
 341                 atomic64_set(&virt_timer_current, timer->expires);
 342                 atomic64_set(&virt_timer_elapsed, 0);
 343                 list_add(&timer->entry, &virt_timer_list);
 344         } else {
 345                 /* Update timer against current base. */
 346                 timer->expires += atomic64_read(&virt_timer_elapsed);
 347                 if (likely((s64) timer->expires <
 348                            (s64) atomic64_read(&virt_timer_current)))
 349                         /* The new timer expires before the current timer. */
 350                         atomic64_set(&virt_timer_current, timer->expires);
 351                 /* Insert new timer into the list. */
 352                 list_add_sorted(timer, &virt_timer_list);
 353         }
 354 }
 355
 356 static void __add_vtimer(struct vtimer_list *timer, int periodic)
 357 {
 358         unsigned long flags;
 359
 360         timer->interval = periodic ? timer->expires : 0;
 361         spin_lock_irqsave(&virt_timer_lock, flags);
 362         internal_add_vtimer(timer);
 363         spin_unlock_irqrestore(&virt_timer_lock, flags);
 364 }
 365
 366 /*
 367  * add_virt_timer - add a oneshot virtual CPU timer
 368  */
 369 void add_virt_timer(struct vtimer_list *timer)
 370 {
 371         __add_vtimer(timer, 0);
 372 }
 373 EXPORT_SYMBOL(add_virt_timer);
 374
 375 /*
 376  * add_virt_timer_int - add an interval virtual CPU timer
 377  */
 378 void add_virt_timer_periodic(struct vtimer_list *timer)
 379 {
 380         __add_vtimer(timer, 1);
 381 }
 382 EXPORT_SYMBOL(add_virt_timer_periodic);
 383
 384 static int __mod_vtimer(struct vtimer_list *timer, u64 expires, int periodic)
 385 {
 386         unsigned long flags;
 387         int rc;
 388
 389         BUG_ON(!timer->function);
 390
 391         if (timer->expires == expires && vtimer_pending(timer))
 392                 return 1;
 393         spin_lock_irqsave(&virt_timer_lock, flags);
 394         rc = vtimer_pending(timer);
 395         if (rc)
 396                 list_del_init(&timer->entry);
 397         timer->interval = periodic ? expires : 0;
 398         timer->expires = expires;
 399         internal_add_vtimer(timer);
 400         spin_unlock_irqrestore(&virt_timer_lock, flags);
 401         return rc;
 402 }
 403
 404 /*
 405  * returns whether it has modified a pending timer (1) or not (0)
 406  */
 407 int mod_virt_timer(struct vtimer_list *timer, u64 expires)
 408 {
 409         return __mod_vtimer(timer, expires, 0);
 410 }
 411 EXPORT_SYMBOL(mod_virt_timer);
 412
 413 /*
 414  * returns whether it has modified a pending timer (1) or not (0)
 415  */
 416 int mod_virt_timer_periodic(struct vtimer_list *timer, u64 expires)
 417 {
 418         return __mod_vtimer(timer, expires, 1);
 419 }
 420 EXPORT_SYMBOL(mod_virt_timer_periodic);
 421
 422 /*
 423  * Delete a virtual timer.
 424  *
 425  * returns whether the deleted timer was pending (1) or not (0)
 426  */
 427 int del_virt_timer(struct vtimer_list *timer)
 428 {
 429         unsigned long flags;
 430
 431         if (!vtimer_pending(timer))
 432                 return 0;
 433         spin_lock_irqsave(&virt_timer_lock, flags);
 434         list_del_init(&timer->entry);
 435         spin_unlock_irqrestore(&virt_timer_lock, flags);
 436         return 1;
 437 }
 438 EXPORT_SYMBOL(del_virt_timer);
 439
 440 /*
 441  * Start the virtual CPU timer on the current CPU.
 442  */
 443 void vtime_init(void)
 444 {
 445         /* set initial cpu timer */
 446         set_vtimer(VTIMER_MAX_SLICE);
 447         /* Setup initial MT scaling values */
 448         if (smp_cpu_mtid) {
 449                 __this_cpu_write(mt_scaling_jiffies, jiffies);
 450                 __this_cpu_write(mt_scaling_mult, 1);
 451                 __this_cpu_write(mt_scaling_div, 1);
 452                 stcctm(MT_DIAG, smp_cpu_mtid + 1, this_cpu_ptr(mt_cycles));
 453         }
 454 }