arch/i386/kernel/vmitime.c

   1 /*
   2  * VMI paravirtual timer support routines.
   3  *
   4  * Copyright (C) 2005, VMware, Inc.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License as published by
   8  * the Free Software Foundation; either version 2 of the License, or
   9  * (at your option) any later version.
  10  *
  11  * This program is distributed in the hope that it will be useful, but
  12  * WITHOUT ANY WARRANTY; without even the implied warranty of
  13  * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
  14  * NON INFRINGEMENT.  See the GNU General Public License for more
  15  * details.
  16  *
  17  * You should have received a copy of the GNU General Public License
  18  * along with this program; if not, write to the Free Software
  19  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
  20  *
  21  * Send feedback to dhecht@vmware.com
  22  *
  23  */
  24
  25 /*
  26  * Portions of this code from arch/i386/kernel/timers/timer_tsc.c.
  27  * Portions of the CONFIG_NO_IDLE_HZ code from arch/s390/kernel/time.c.
  28  * See comments there for proper credits.
  29  */
  30
  31 #include <linux/spinlock.h>
  32 #include <linux/init.h>
  33 #include <linux/errno.h>
  34 #include <linux/jiffies.h>
  35 #include <linux/interrupt.h>
  36 #include <linux/kernel_stat.h>
  37 #include <linux/rcupdate.h>
  38 #include <linux/clocksource.h>
  39
  40 #include <asm/timer.h>
  41 #include <asm/io.h>
  42 #include <asm/apic.h>
  43 #include <asm/div64.h>
  44 #include <asm/timer.h>
  45 #include <asm/desc.h>
  46
  47 #include <asm/vmi.h>
  48 #include <asm/vmi_time.h>
  49
  50 #include <mach_timer.h>
  51 #include <io_ports.h>
  52
  53 #ifdef CONFIG_X86_LOCAL_APIC
  54 #define VMI_ALARM_WIRING VMI_ALARM_WIRED_LVTT
  55 #else
  56 #define VMI_ALARM_WIRING VMI_ALARM_WIRED_IRQ0
  57 #endif
  58
  59 /* Cached VMI operations */
  60 struct vmi_timer_ops vmi_timer_ops;
  61
  62 #ifdef CONFIG_NO_IDLE_HZ
  63
  64 /* /proc/sys/kernel/hz_timer state. */
  65 int sysctl_hz_timer;
  66
  67 /* Some stats */
  68 static DEFINE_PER_CPU(unsigned long, vmi_idle_no_hz_irqs);
  69 static DEFINE_PER_CPU(unsigned long, vmi_idle_no_hz_jiffies);
  70 static DEFINE_PER_CPU(unsigned long, idle_start_jiffies);
  71
  72 #endif /* CONFIG_NO_IDLE_HZ */
  73
  74 /* Number of alarms per second. By default this is CONFIG_VMI_ALARM_HZ. */
  75 static int alarm_hz = CONFIG_VMI_ALARM_HZ;
  76
  77 /* Cache of the value get_cycle_frequency / HZ. */
  78 static signed long long cycles_per_jiffy;
  79
  80 /* Cache of the value get_cycle_frequency / alarm_hz. */
  81 static signed long long cycles_per_alarm;
  82
  83 /* The number of cycles accounted for by the 'jiffies'/'xtime' count.
  84  * Protected by xtime_lock. */
  85 static unsigned long long real_cycles_accounted_system;
  86
  87 /* The number of cycles accounted for by update_process_times(), per cpu. */
  88 static DEFINE_PER_CPU(unsigned long long, process_times_cycles_accounted_cpu);
  89
  90 /* The number of stolen cycles accounted, per cpu. */
  91 static DEFINE_PER_CPU(unsigned long long, stolen_cycles_accounted_cpu);
  92
  93 /* Clock source. */
  94 static cycle_t read_real_cycles(void)
  95 {
  96         return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_REAL);
  97 }
  98
  99 static cycle_t read_available_cycles(void)
 100 {
 101         return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_AVAILABLE);
 102 }
 103
 104 #if 0
 105 static cycle_t read_stolen_cycles(void)
 106 {
 107         return vmi_timer_ops.get_cycle_counter(VMI_CYCLES_STOLEN);
 108 }
 109 #endif  /*  0  */
 110
 111 static struct clocksource clocksource_vmi = {
 112         .name                   = "vmi-timer",
 113         .rating                 = 450,
 114         .read                   = read_real_cycles,
 115         .mask                   = CLOCKSOURCE_MASK(64),
 116         .mult                   = 0, /* to be set */
 117         .shift                  = 22,
 118         .flags                  = CLOCK_SOURCE_IS_CONTINUOUS,
 119 };
 120
 121
 122 /* Timer interrupt handler. */
 123 static irqreturn_t vmi_timer_interrupt(int irq, void *dev_id);
 124
 125 static struct irqaction vmi_timer_irq  = {
 126         .handler = vmi_timer_interrupt,
 127         .flags = IRQF_DISABLED,
 128         .mask = CPU_MASK_NONE,
 129         .name = "VMI-alarm",
 130 };
 131
 132 /* Alarm rate */
 133 static int __init vmi_timer_alarm_rate_setup(char* str)
 134 {
 135         int alarm_rate;
 136         if (get_option(&str, &alarm_rate) == 1 && alarm_rate > 0) {
 137                 alarm_hz = alarm_rate;
 138                 printk(KERN_WARNING "VMI timer alarm HZ set to %d\n", alarm_hz);
 139         }
 140         return 1;
 141 }
 142 __setup("vmi_timer_alarm_hz=", vmi_timer_alarm_rate_setup);
 143
 144
 145 /* Initialization */
 146 static void vmi_get_wallclock_ts(struct timespec *ts)
 147 {
 148         unsigned long long wallclock;
 149         wallclock = vmi_timer_ops.get_wallclock(); // nsec units
 150         ts->tv_nsec = do_div(wallclock, 1000000000);
 151         ts->tv_sec = wallclock;
 152 }
 153
 154 unsigned long vmi_get_wallclock(void)
 155 {
 156         struct timespec ts;
 157         vmi_get_wallclock_ts(&ts);
 158         return ts.tv_sec;
 159 }
 160
 161 int vmi_set_wallclock(unsigned long now)
 162 {
 163         return -1;
 164 }
 165
 166 unsigned long long vmi_get_sched_cycles(void)
 167 {
 168         return read_available_cycles();
 169 }
 170
 171 unsigned long vmi_cpu_khz(void)
 172 {
 173         unsigned long long khz;
 174
 175         khz = vmi_timer_ops.get_cycle_frequency();
 176         (void)do_div(khz, 1000);
 177         return khz;
 178 }
 179
 180 void __init vmi_time_init(void)
 181 {
 182         unsigned long long cycles_per_sec, cycles_per_msec;
 183         unsigned long flags;
 184
 185         local_irq_save(flags);
 186         setup_irq(0, &vmi_timer_irq);
 187 #ifdef CONFIG_X86_LOCAL_APIC
 188         set_intr_gate(LOCAL_TIMER_VECTOR, apic_vmi_timer_interrupt);
 189 #endif
 190
 191         real_cycles_accounted_system = read_real_cycles();
 192         per_cpu(process_times_cycles_accounted_cpu, 0) = read_available_cycles();
 193
 194         cycles_per_sec = vmi_timer_ops.get_cycle_frequency();
 195         cycles_per_jiffy = cycles_per_sec;
 196         (void)do_div(cycles_per_jiffy, HZ);
 197         cycles_per_alarm = cycles_per_sec;
 198         (void)do_div(cycles_per_alarm, alarm_hz);
 199         cycles_per_msec = cycles_per_sec;
 200         (void)do_div(cycles_per_msec, 1000);
 201
 202         printk(KERN_WARNING "VMI timer cycles/sec = %llu ; cycles/jiffy = %llu ;"
 203                "cycles/alarm = %llu\n", cycles_per_sec, cycles_per_jiffy,
 204                cycles_per_alarm);
 205
 206         clocksource_vmi.mult = clocksource_khz2mult(cycles_per_msec,
 207                                                     clocksource_vmi.shift);
 208         if (clocksource_register(&clocksource_vmi))
 209                 printk(KERN_WARNING "Error registering VMITIME clocksource.");
 210
 211         /* Disable PIT. */
 212         outb_p(0x3a, PIT_MODE); /* binary, mode 5, LSB/MSB, ch 0 */
 213
 214         /* schedule the alarm. do this in phase with process_times_cycles_accounted_cpu
 215          * reduce the latency calling update_process_times. */
 216         vmi_timer_ops.set_alarm(
 217                       VMI_ALARM_WIRED_IRQ0 | VMI_ALARM_IS_PERIODIC | VMI_CYCLES_AVAILABLE,
 218                       per_cpu(process_times_cycles_accounted_cpu, 0) + cycles_per_alarm,
 219                       cycles_per_alarm);
 220
 221         local_irq_restore(flags);
 222 }
 223
 224 #ifdef CONFIG_X86_LOCAL_APIC
 225
 226 void __init vmi_timer_setup_boot_alarm(void)
 227 {
 228         local_irq_disable();
 229
 230         /* Route the interrupt to the correct vector. */
 231         apic_write_around(APIC_LVTT, LOCAL_TIMER_VECTOR);
 232
 233         /* Cancel the IRQ0 wired alarm, and setup the LVTT alarm. */
 234         vmi_timer_ops.cancel_alarm(VMI_CYCLES_AVAILABLE);
 235         vmi_timer_ops.set_alarm(
 236                       VMI_ALARM_WIRED_LVTT | VMI_ALARM_IS_PERIODIC | VMI_CYCLES_AVAILABLE,
 237                       per_cpu(process_times_cycles_accounted_cpu, 0) + cycles_per_alarm,
 238                       cycles_per_alarm);
 239         local_irq_enable();
 240 }
 241
 242 /* Initialize the time accounting variables for an AP on an SMP system.
 243  * Also, set the local alarm for the AP. */
 244 void __devinit vmi_timer_setup_secondary_alarm(void)
 245 {
 246         int cpu = smp_processor_id();
 247
 248         /* Route the interrupt to the correct vector. */
 249         apic_write_around(APIC_LVTT, LOCAL_TIMER_VECTOR);
 250
 251         per_cpu(process_times_cycles_accounted_cpu, cpu) = read_available_cycles();
 252
 253         vmi_timer_ops.set_alarm(
 254                       VMI_ALARM_WIRED_LVTT | VMI_ALARM_IS_PERIODIC | VMI_CYCLES_AVAILABLE,
 255                       per_cpu(process_times_cycles_accounted_cpu, cpu) + cycles_per_alarm,
 256                       cycles_per_alarm);
 257 }
 258
 259 #endif
 260
 261 /* Update system wide (real) time accounting (e.g. jiffies, xtime). */
 262 static void vmi_account_real_cycles(unsigned long long cur_real_cycles)
 263 {
 264         long long cycles_not_accounted;
 265
 266         write_seqlock(&xtime_lock);
 267
 268         cycles_not_accounted = cur_real_cycles - real_cycles_accounted_system;
 269         while (cycles_not_accounted >= cycles_per_jiffy) {
 270                 /* systems wide jiffies. */
 271                 do_timer(1);
 272
 273                 cycles_not_accounted -= cycles_per_jiffy;
 274                 real_cycles_accounted_system += cycles_per_jiffy;
 275         }
 276
 277         write_sequnlock(&xtime_lock);
 278 }
 279
 280 /* Update per-cpu process times. */
 281 static void vmi_account_process_times_cycles(struct pt_regs *regs, int cpu,
 282                                              unsigned long long cur_process_times_cycles)
 283 {
 284         long long cycles_not_accounted;
 285         cycles_not_accounted = cur_process_times_cycles -
 286                 per_cpu(process_times_cycles_accounted_cpu, cpu);
 287
 288         while (cycles_not_accounted >= cycles_per_jiffy) {
 289                 /* Account time to the current process.  This includes
 290                  * calling into the scheduler to decrement the timeslice
 291                  * and possibly reschedule.*/
 292                 update_process_times(user_mode(regs));
 293                 /* XXX handle /proc/profile multiplier.  */
 294                 profile_tick(CPU_PROFILING);
 295
 296                 cycles_not_accounted -= cycles_per_jiffy;
 297                 per_cpu(process_times_cycles_accounted_cpu, cpu) += cycles_per_jiffy;
 298         }
 299 }
 300
 301 #ifdef CONFIG_NO_IDLE_HZ
 302 /* Update per-cpu idle times.  Used when a no-hz halt is ended. */
 303 static void vmi_account_no_hz_idle_cycles(int cpu,
 304                                           unsigned long long cur_process_times_cycles)
 305 {
 306         long long cycles_not_accounted;
 307         unsigned long no_idle_hz_jiffies = 0;
 308
 309         cycles_not_accounted = cur_process_times_cycles -
 310                 per_cpu(process_times_cycles_accounted_cpu, cpu);
 311
 312         while (cycles_not_accounted >= cycles_per_jiffy) {
 313                 no_idle_hz_jiffies++;
 314                 cycles_not_accounted -= cycles_per_jiffy;
 315                 per_cpu(process_times_cycles_accounted_cpu, cpu) += cycles_per_jiffy;
 316         }
 317         /* Account time to the idle process. */
 318         account_steal_time(idle_task(cpu), jiffies_to_cputime(no_idle_hz_jiffies));
 319 }
 320 #endif
 321
 322 /* Update per-cpu stolen time. */
 323 static void vmi_account_stolen_cycles(int cpu,
 324                                       unsigned long long cur_real_cycles,
 325                                       unsigned long long cur_avail_cycles)
 326 {
 327         long long stolen_cycles_not_accounted;
 328         unsigned long stolen_jiffies = 0;
 329
 330         if (cur_real_cycles < cur_avail_cycles)
 331                 return;
 332
 333         stolen_cycles_not_accounted = cur_real_cycles - cur_avail_cycles -
 334                 per_cpu(stolen_cycles_accounted_cpu, cpu);
 335
 336         while (stolen_cycles_not_accounted >= cycles_per_jiffy) {
 337                 stolen_jiffies++;
 338                 stolen_cycles_not_accounted -= cycles_per_jiffy;
 339                 per_cpu(stolen_cycles_accounted_cpu, cpu) += cycles_per_jiffy;
 340         }
 341         /* HACK: pass NULL to force time onto cpustat->steal. */
 342         account_steal_time(NULL, jiffies_to_cputime(stolen_jiffies));
 343 }
 344
 345 /* Body of either IRQ0 interrupt handler (UP no local-APIC) or
 346  * local-APIC LVTT interrupt handler (UP & local-APIC or SMP). */
 347 static void vmi_local_timer_interrupt(int cpu)
 348 {
 349         unsigned long long cur_real_cycles, cur_process_times_cycles;
 350
 351         cur_real_cycles = read_real_cycles();
 352         cur_process_times_cycles = read_available_cycles();
 353         /* Update system wide (real) time state (xtime, jiffies). */
 354         vmi_account_real_cycles(cur_real_cycles);
 355         /* Update per-cpu process times. */
 356         vmi_account_process_times_cycles(get_irq_regs(), cpu, cur_process_times_cycles);
 357         /* Update time stolen from this cpu by the hypervisor. */
 358         vmi_account_stolen_cycles(cpu, cur_real_cycles, cur_process_times_cycles);
 359 }
 360
 361 #ifdef CONFIG_NO_IDLE_HZ
 362
 363 /* Must be called only from idle loop, with interrupts disabled. */
 364 int vmi_stop_hz_timer(void)
 365 {
 366         /* Note that cpu_set, cpu_clear are (SMP safe) atomic on x86. */
 367
 368         unsigned long seq, next;
 369         unsigned long long real_cycles_expiry;
 370         int cpu = smp_processor_id();
 371
 372         BUG_ON(!irqs_disabled());
 373         if (sysctl_hz_timer != 0)
 374                 return 0;
 375
 376         cpu_set(cpu, nohz_cpu_mask);
 377         smp_mb();
 378
 379         if (rcu_needs_cpu(cpu) || local_softirq_pending() ||
 380             (next = next_timer_interrupt(),
 381              time_before_eq(next, jiffies + HZ/CONFIG_VMI_ALARM_HZ))) {
 382                 cpu_clear(cpu, nohz_cpu_mask);
 383                 return 0;
 384         }
 385
 386         /* Convert jiffies to the real cycle counter. */
 387         do {
 388                 seq = read_seqbegin(&xtime_lock);
 389                 real_cycles_expiry = real_cycles_accounted_system +
 390                         (long)(next - jiffies) * cycles_per_jiffy;
 391         } while (read_seqretry(&xtime_lock, seq));
 392
 393         /* This cpu is going idle. Disable the periodic alarm. */
 394         vmi_timer_ops.cancel_alarm(VMI_CYCLES_AVAILABLE);
 395         per_cpu(idle_start_jiffies, cpu) = jiffies;
 396         /* Set the real time alarm to expire at the next event. */
 397         vmi_timer_ops.set_alarm(
 398                 VMI_ALARM_WIRING | VMI_ALARM_IS_ONESHOT | VMI_CYCLES_REAL,
 399                 real_cycles_expiry, 0);
 400         return 1;
 401 }
 402
 403 static void vmi_reenable_hz_timer(int cpu)
 404 {
 405         /* For /proc/vmi/info idle_hz stat. */
 406         per_cpu(vmi_idle_no_hz_jiffies, cpu) += jiffies - per_cpu(idle_start_jiffies, cpu);
 407         per_cpu(vmi_idle_no_hz_irqs, cpu)++;
 408
 409         /* Don't bother explicitly cancelling the one-shot alarm -- at
 410          * worse we will receive a spurious timer interrupt. */
 411         vmi_timer_ops.set_alarm(
 412                       VMI_ALARM_WIRING | VMI_ALARM_IS_PERIODIC | VMI_CYCLES_AVAILABLE,
 413                       per_cpu(process_times_cycles_accounted_cpu, cpu) + cycles_per_alarm,
 414                       cycles_per_alarm);
 415         /* Indicate this cpu is no longer nohz idle. */
 416         cpu_clear(cpu, nohz_cpu_mask);
 417 }
 418
 419 /* Called from interrupt handlers when (local) HZ timer is disabled. */
 420 void vmi_account_time_restart_hz_timer(void)
 421 {
 422         unsigned long long cur_real_cycles, cur_process_times_cycles;
 423         int cpu = smp_processor_id();
 424
 425         BUG_ON(!irqs_disabled());
 426         /* Account the time during which the HZ timer was disabled. */
 427         cur_real_cycles = read_real_cycles();
 428         cur_process_times_cycles = read_available_cycles();
 429         /* Update system wide (real) time state (xtime, jiffies). */
 430         vmi_account_real_cycles(cur_real_cycles);
 431         /* Update per-cpu idle times. */
 432         vmi_account_no_hz_idle_cycles(cpu, cur_process_times_cycles);
 433         /* Update time stolen from this cpu by the hypervisor. */
 434         vmi_account_stolen_cycles(cpu, cur_real_cycles, cur_process_times_cycles);
 435         /* Reenable the hz timer. */
 436         vmi_reenable_hz_timer(cpu);
 437 }
 438
 439 #endif /* CONFIG_NO_IDLE_HZ */
 440
 441 /* UP (and no local-APIC) VMI-timer alarm interrupt handler.
 442  * Handler for IRQ0. Not used when SMP or X86_LOCAL_APIC after
 443  * APIC setup and setup_boot_vmi_alarm() is called.  */
 444 static irqreturn_t vmi_timer_interrupt(int irq, void *dev_id)
 445 {
 446         vmi_local_timer_interrupt(smp_processor_id());
 447         return IRQ_HANDLED;
 448 }
 449
 450 #ifdef CONFIG_X86_LOCAL_APIC
 451
 452 /* SMP VMI-timer alarm interrupt handler. Handler for LVTT vector.
 453  * Also used in UP when CONFIG_X86_LOCAL_APIC.
 454  * The wrapper code is from arch/i386/kernel/apic.c#smp_apic_timer_interrupt. */
 455 void smp_apic_vmi_timer_interrupt(struct pt_regs *regs)
 456 {
 457         struct pt_regs *old_regs = set_irq_regs(regs);
 458         int cpu = smp_processor_id();
 459
 460         /*
 461          * the NMI deadlock-detector uses this.
 462          */
 463         per_cpu(irq_stat,cpu).apic_timer_irqs++;
 464
 465         /*
 466          * NOTE! We'd better ACK the irq immediately,
 467          * because timer handling can be slow.
 468          */
 469         ack_APIC_irq();
 470
 471         /*
 472          * update_process_times() expects us to have done irq_enter().
 473          * Besides, if we don't timer interrupts ignore the global
 474          * interrupt lock, which is the WrongThing (tm) to do.
 475          */
 476         irq_enter();
 477         vmi_local_timer_interrupt(cpu);
 478         irq_exit();
 479         set_irq_regs(old_regs);
 480 }
 481
 482 #endif  /* CONFIG_X86_LOCAL_APIC */