arch/x86/xen/time.c

   1 /*
   2  * Xen time implementation.
   3  *
   4  * This is implemented in terms of a clocksource driver which uses
   5  * the hypervisor clock as a nanosecond timebase, and a clockevent
   6  * driver which uses the hypervisor's timer mechanism.
   7  *
   8  * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
   9  */
  10 #include <linux/kernel.h>
  11 #include <linux/interrupt.h>
  12 #include <linux/clocksource.h>
  13 #include <linux/clockchips.h>
  14 #include <linux/gfp.h>
  15 #include <linux/slab.h>
  16 #include <linux/pvclock_gtod.h>
  17 #include <linux/timekeeper_internal.h>
  18
  19 #include <asm/pvclock.h>
  20 #include <asm/xen/hypervisor.h>
  21 #include <asm/xen/hypercall.h>
  22
  23 #include <xen/events.h>
  24 #include <xen/features.h>
  25 #include <xen/interface/xen.h>
  26 #include <xen/interface/vcpu.h>
  27
  28 #include "xen-ops.h"
  29
  30 /* Xen may fire a timer up to this many ns early */
  31 #define TIMER_SLOP      100000
  32
  33 /* Get the TSC speed from Xen */
  34 static unsigned long xen_tsc_khz(void)
  35 {
  36         struct pvclock_vcpu_time_info *info =
  37                 &HYPERVISOR_shared_info->vcpu_info[0].time;
  38
  39         return pvclock_tsc_khz(info);
  40 }
  41
  42 u64 xen_clocksource_read(void)
  43 {
  44         struct pvclock_vcpu_time_info *src;
  45         u64 ret;
  46
  47         preempt_disable_notrace();
  48         src = &__this_cpu_read(xen_vcpu)->time;
  49         ret = pvclock_clocksource_read(src);
  50         preempt_enable_notrace();
  51         return ret;
  52 }
  53
  54 static u64 xen_clocksource_get_cycles(struct clocksource *cs)
  55 {
  56         return xen_clocksource_read();
  57 }
  58
  59 static void xen_read_wallclock(struct timespec *ts)
  60 {
  61         struct shared_info *s = HYPERVISOR_shared_info;
  62         struct pvclock_wall_clock *wall_clock = &(s->wc);
  63         struct pvclock_vcpu_time_info *vcpu_time;
  64
  65         vcpu_time = &get_cpu_var(xen_vcpu)->time;
  66         pvclock_read_wallclock(wall_clock, vcpu_time, ts);
  67         put_cpu_var(xen_vcpu);
  68 }
  69
  70 static void xen_get_wallclock(struct timespec *now)
  71 {
  72         xen_read_wallclock(now);
  73 }
  74
  75 static int xen_set_wallclock(const struct timespec *now)
  76 {
  77         return -1;
  78 }
  79
  80 static int xen_pvclock_gtod_notify(struct notifier_block *nb,
  81                                    unsigned long was_set, void *priv)
  82 {
  83         /* Protected by the calling core code serialization */
  84         static struct timespec64 next_sync;
  85
  86         struct xen_platform_op op;
  87         struct timespec64 now;
  88         struct timekeeper *tk = priv;
  89         static bool settime64_supported = true;
  90         int ret;
  91
  92         now.tv_sec = tk->xtime_sec;
  93         now.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
  94
  95         /*
  96          * We only take the expensive HV call when the clock was set
  97          * or when the 11 minutes RTC synchronization time elapsed.
  98          */
  99         if (!was_set && timespec64_compare(&now, &next_sync) < 0)
 100                 return NOTIFY_OK;
 101
 102 again:
 103         if (settime64_supported) {
 104                 op.cmd = XENPF_settime64;
 105                 op.u.settime64.mbz = 0;
 106                 op.u.settime64.secs = now.tv_sec;
 107                 op.u.settime64.nsecs = now.tv_nsec;
 108                 op.u.settime64.system_time = xen_clocksource_read();
 109         } else {
 110                 op.cmd = XENPF_settime32;
 111                 op.u.settime32.secs = now.tv_sec;
 112                 op.u.settime32.nsecs = now.tv_nsec;
 113                 op.u.settime32.system_time = xen_clocksource_read();
 114         }
 115
 116         ret = HYPERVISOR_platform_op(&op);
 117
 118         if (ret == -ENOSYS && settime64_supported) {
 119                 settime64_supported = false;
 120                 goto again;
 121         }
 122         if (ret < 0)
 123                 return NOTIFY_BAD;
 124
 125         /*
 126          * Move the next drift compensation time 11 minutes
 127          * ahead. That's emulating the sync_cmos_clock() update for
 128          * the hardware RTC.
 129          */
 130         next_sync = now;
 131         next_sync.tv_sec += 11 * 60;
 132
 133         return NOTIFY_OK;
 134 }
 135
 136 static struct notifier_block xen_pvclock_gtod_notifier = {
 137         .notifier_call = xen_pvclock_gtod_notify,
 138 };
 139
 140 static struct clocksource xen_clocksource __read_mostly = {
 141         .name = "xen",
 142         .rating = 400,
 143         .read = xen_clocksource_get_cycles,
 144         .mask = ~0,
 145         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
 146 };
 147
 148 /*
 149    Xen clockevent implementation
 150
 151    Xen has two clockevent implementations:
 152
 153    The old timer_op one works with all released versions of Xen prior
 154    to version 3.0.4.  This version of the hypervisor provides a
 155    single-shot timer with nanosecond resolution.  However, sharing the
 156    same event channel is a 100Hz tick which is delivered while the
 157    vcpu is running.  We don't care about or use this tick, but it will
 158    cause the core time code to think the timer fired too soon, and
 159    will end up resetting it each time.  It could be filtered, but
 160    doing so has complications when the ktime clocksource is not yet
 161    the xen clocksource (ie, at boot time).
 162
 163    The new vcpu_op-based timer interface allows the tick timer period
 164    to be changed or turned off.  The tick timer is not useful as a
 165    periodic timer because events are only delivered to running vcpus.
 166    The one-shot timer can report when a timeout is in the past, so
 167    set_next_event is capable of returning -ETIME when appropriate.
 168    This interface is used when available.
 169 */
 170
 171
 172 /*
 173   Get a hypervisor absolute time.  In theory we could maintain an
 174   offset between the kernel's time and the hypervisor's time, and
 175   apply that to a kernel's absolute timeout.  Unfortunately the
 176   hypervisor and kernel times can drift even if the kernel is using
 177   the Xen clocksource, because ntp can warp the kernel's clocksource.
 178 */
 179 static s64 get_abs_timeout(unsigned long delta)
 180 {
 181         return xen_clocksource_read() + delta;
 182 }
 183
 184 static int xen_timerop_shutdown(struct clock_event_device *evt)
 185 {
 186         /* cancel timeout */
 187         HYPERVISOR_set_timer_op(0);
 188
 189         return 0;
 190 }
 191
 192 static int xen_timerop_set_next_event(unsigned long delta,
 193                                       struct clock_event_device *evt)
 194 {
 195         WARN_ON(!clockevent_state_oneshot(evt));
 196
 197         if (HYPERVISOR_set_timer_op(get_abs_timeout(delta)) < 0)
 198                 BUG();
 199
 200         /* We may have missed the deadline, but there's no real way of
 201            knowing for sure.  If the event was in the past, then we'll
 202            get an immediate interrupt. */
 203
 204         return 0;
 205 }
 206
 207 static const struct clock_event_device xen_timerop_clockevent = {
 208         .name                   = "xen",
 209         .features               = CLOCK_EVT_FEAT_ONESHOT,
 210
 211         .max_delta_ns           = 0xffffffff,
 212         .max_delta_ticks        = 0xffffffff,
 213         .min_delta_ns           = TIMER_SLOP,
 214         .min_delta_ticks        = TIMER_SLOP,
 215
 216         .mult                   = 1,
 217         .shift                  = 0,
 218         .rating                 = 500,
 219
 220         .set_state_shutdown     = xen_timerop_shutdown,
 221         .set_next_event         = xen_timerop_set_next_event,
 222 };
 223
 224 static int xen_vcpuop_shutdown(struct clock_event_device *evt)
 225 {
 226         int cpu = smp_processor_id();
 227
 228         if (HYPERVISOR_vcpu_op(VCPUOP_stop_singleshot_timer, xen_vcpu_nr(cpu),
 229                                NULL) ||
 230             HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, xen_vcpu_nr(cpu),
 231                                NULL))
 232                 BUG();
 233
 234         return 0;
 235 }
 236
 237 static int xen_vcpuop_set_oneshot(struct clock_event_device *evt)
 238 {
 239         int cpu = smp_processor_id();
 240
 241         if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, xen_vcpu_nr(cpu),
 242                                NULL))
 243                 BUG();
 244
 245         return 0;
 246 }
 247
 248 static int xen_vcpuop_set_next_event(unsigned long delta,
 249                                      struct clock_event_device *evt)
 250 {
 251         int cpu = smp_processor_id();
 252         struct vcpu_set_singleshot_timer single;
 253         int ret;
 254
 255         WARN_ON(!clockevent_state_oneshot(evt));
 256
 257         single.timeout_abs_ns = get_abs_timeout(delta);
 258         /* Get an event anyway, even if the timeout is already expired */
 259         single.flags = 0;
 260
 261         ret = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, xen_vcpu_nr(cpu),
 262                                  &single);
 263         BUG_ON(ret != 0);
 264
 265         return ret;
 266 }
 267
 268 static const struct clock_event_device xen_vcpuop_clockevent = {
 269         .name = "xen",
 270         .features = CLOCK_EVT_FEAT_ONESHOT,
 271
 272         .max_delta_ns = 0xffffffff,
 273         .max_delta_ticks = 0xffffffff,
 274         .min_delta_ns = TIMER_SLOP,
 275         .min_delta_ticks = TIMER_SLOP,
 276
 277         .mult = 1,
 278         .shift = 0,
 279         .rating = 500,
 280
 281         .set_state_shutdown = xen_vcpuop_shutdown,
 282         .set_state_oneshot = xen_vcpuop_set_oneshot,
 283         .set_next_event = xen_vcpuop_set_next_event,
 284 };
 285
 286 static const struct clock_event_device *xen_clockevent =
 287         &xen_timerop_clockevent;
 288
 289 struct xen_clock_event_device {
 290         struct clock_event_device evt;
 291         char name[16];
 292 };
 293 static DEFINE_PER_CPU(struct xen_clock_event_device, xen_clock_events) = { .evt.irq = -1 };
 294
 295 static irqreturn_t xen_timer_interrupt(int irq, void *dev_id)
 296 {
 297         struct clock_event_device *evt = this_cpu_ptr(&xen_clock_events.evt);
 298         irqreturn_t ret;
 299
 300         ret = IRQ_NONE;
 301         if (evt->event_handler) {
 302                 evt->event_handler(evt);
 303                 ret = IRQ_HANDLED;
 304         }
 305
 306         return ret;
 307 }
 308
 309 void xen_teardown_timer(int cpu)
 310 {
 311         struct clock_event_device *evt;
 312         evt = &per_cpu(xen_clock_events, cpu).evt;
 313
 314         if (evt->irq >= 0) {
 315                 unbind_from_irqhandler(evt->irq, NULL);
 316                 evt->irq = -1;
 317         }
 318 }
 319
 320 void xen_setup_timer(int cpu)
 321 {
 322         struct xen_clock_event_device *xevt = &per_cpu(xen_clock_events, cpu);
 323         struct clock_event_device *evt = &xevt->evt;
 324         int irq;
 325
 326         WARN(evt->irq >= 0, "IRQ%d for CPU%d is already allocated\n", evt->irq, cpu);
 327         if (evt->irq >= 0)
 328                 xen_teardown_timer(cpu);
 329
 330         printk(KERN_INFO "installing Xen timer for CPU %d\n", cpu);
 331
 332         snprintf(xevt->name, sizeof(xevt->name), "timer%d", cpu);
 333
 334         irq = bind_virq_to_irqhandler(VIRQ_TIMER, cpu, xen_timer_interrupt,
 335                                       IRQF_PERCPU|IRQF_NOBALANCING|IRQF_TIMER|
 336                                       IRQF_FORCE_RESUME|IRQF_EARLY_RESUME,
 337                                       xevt->name, NULL);
 338         (void)xen_set_irq_priority(irq, XEN_IRQ_PRIORITY_MAX);
 339
 340         memcpy(evt, xen_clockevent, sizeof(*evt));
 341
 342         evt->cpumask = cpumask_of(cpu);
 343         evt->irq = irq;
 344 }
 345
 346
 347 void xen_setup_cpu_clockevents(void)
 348 {
 349         clockevents_register_device(this_cpu_ptr(&xen_clock_events.evt));
 350 }
 351
 352 void xen_timer_resume(void)
 353 {
 354         int cpu;
 355
 356         pvclock_resume();
 357
 358         if (xen_clockevent != &xen_vcpuop_clockevent)
 359                 return;
 360
 361         for_each_online_cpu(cpu) {
 362                 if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer,
 363                                        xen_vcpu_nr(cpu), NULL))
 364                         BUG();
 365         }
 366 }
 367
 368 static const struct pv_time_ops xen_time_ops __initconst = {
 369         .sched_clock = xen_clocksource_read,
 370         .steal_clock = xen_steal_clock,
 371 };
 372
 373 static void __init xen_time_init(void)
 374 {
 375         int cpu = smp_processor_id();
 376         struct timespec tp;
 377
 378         /* As Dom0 is never moved, no penalty on using TSC there */
 379         if (xen_initial_domain())
 380                 xen_clocksource.rating = 275;
 381
 382         clocksource_register_hz(&xen_clocksource, NSEC_PER_SEC);
 383
 384         if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, xen_vcpu_nr(cpu),
 385                                NULL) == 0) {
 386                 /* Successfully turned off 100Hz tick, so we have the
 387                    vcpuop-based timer interface */
 388                 printk(KERN_DEBUG "Xen: using vcpuop timer interface\n");
 389                 xen_clockevent = &xen_vcpuop_clockevent;
 390         }
 391
 392         /* Set initial system time with full resolution */
 393         xen_read_wallclock(&tp);
 394         do_settimeofday(&tp);
 395
 396         setup_force_cpu_cap(X86_FEATURE_TSC);
 397
 398         xen_setup_runstate_info(cpu);
 399         xen_setup_timer(cpu);
 400         xen_setup_cpu_clockevents();
 401
 402         xen_time_setup_guest();
 403
 404         if (xen_initial_domain())
 405                 pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
 406 }
 407
 408 void __ref xen_init_time_ops(void)
 409 {
 410         pv_time_ops = xen_time_ops;
 411
 412         x86_init.timers.timer_init = xen_time_init;
 413         x86_init.timers.setup_percpu_clockev = x86_init_noop;
 414         x86_cpuinit.setup_percpu_clockev = x86_init_noop;
 415
 416         x86_platform.calibrate_tsc = xen_tsc_khz;
 417         x86_platform.get_wallclock = xen_get_wallclock;
 418         /* Dom0 uses the native method to set the hardware RTC. */
 419         if (!xen_initial_domain())
 420                 x86_platform.set_wallclock = xen_set_wallclock;
 421 }
 422
 423 #ifdef CONFIG_XEN_PVHVM
 424 static void xen_hvm_setup_cpu_clockevents(void)
 425 {
 426         int cpu = smp_processor_id();
 427         xen_setup_runstate_info(cpu);
 428         /*
 429          * xen_setup_timer(cpu) - snprintf is bad in atomic context. Hence
 430          * doing it xen_hvm_cpu_notify (which gets called by smp_init during
 431          * early bootup and also during CPU hotplug events).
 432          */
 433         xen_setup_cpu_clockevents();
 434 }
 435
 436 void __init xen_hvm_init_time_ops(void)
 437 {
 438         /*
 439          * vector callback is needed otherwise we cannot receive interrupts
 440          * on cpu > 0 and at this point we don't know how many cpus are
 441          * available.
 442          */
 443         if (!xen_have_vector_callback)
 444                 return;
 445
 446         if (!xen_feature(XENFEAT_hvm_safe_pvclock)) {
 447                 printk(KERN_INFO "Xen doesn't support pvclock on HVM,"
 448                                 "disable pv timer\n");
 449                 return;
 450         }
 451
 452         pv_time_ops = xen_time_ops;
 453         x86_init.timers.setup_percpu_clockev = xen_time_init;
 454         x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents;
 455
 456         x86_platform.calibrate_tsc = xen_tsc_khz;
 457         x86_platform.get_wallclock = xen_get_wallclock;
 458         x86_platform.set_wallclock = xen_set_wallclock;
 459 }
 460 #endif