arch/x86/xen/time.c

   1 // SPDX-License-Identifier: GPL-2.0
   2 /*
   3  * Xen time implementation.
   4  *
   5  * This is implemented in terms of a clocksource driver which uses
   6  * the hypervisor clock as a nanosecond timebase, and a clockevent
   7  * driver which uses the hypervisor's timer mechanism.
   8  *
   9  * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
  10  */
  11 #include <linux/kernel.h>
  12 #include <linux/interrupt.h>
  13 #include <linux/clocksource.h>
  14 #include <linux/clockchips.h>
  15 #include <linux/gfp.h>
  16 #include <linux/slab.h>
  17 #include <linux/pvclock_gtod.h>
  18 #include <linux/timekeeper_internal.h>
  19
  20 #include <asm/pvclock.h>
  21 #include <asm/xen/hypervisor.h>
  22 #include <asm/xen/hypercall.h>
  23
  24 #include <xen/events.h>
  25 #include <xen/features.h>
  26 #include <xen/interface/xen.h>
  27 #include <xen/interface/vcpu.h>
  28
  29 #include "xen-ops.h"
  30
  31 /* Xen may fire a timer up to this many ns early */
  32 #define TIMER_SLOP      100000
  33
  34 /* Get the TSC speed from Xen */
  35 static unsigned long xen_tsc_khz(void)
  36 {
  37         struct pvclock_vcpu_time_info *info =
  38                 &HYPERVISOR_shared_info->vcpu_info[0].time;
  39
  40         return pvclock_tsc_khz(info);
  41 }
  42
  43 u64 xen_clocksource_read(void)
  44 {
  45         struct pvclock_vcpu_time_info *src;
  46         u64 ret;
  47
  48         preempt_disable_notrace();
  49         src = &__this_cpu_read(xen_vcpu)->time;
  50         ret = pvclock_clocksource_read(src);
  51         preempt_enable_notrace();
  52         return ret;
  53 }
  54
  55 static u64 xen_clocksource_get_cycles(struct clocksource *cs)
  56 {
  57         return xen_clocksource_read();
  58 }
  59
  60 static void xen_read_wallclock(struct timespec *ts)
  61 {
  62         struct shared_info *s = HYPERVISOR_shared_info;
  63         struct pvclock_wall_clock *wall_clock = &(s->wc);
  64         struct pvclock_vcpu_time_info *vcpu_time;
  65
  66         vcpu_time = &get_cpu_var(xen_vcpu)->time;
  67         pvclock_read_wallclock(wall_clock, vcpu_time, ts);
  68         put_cpu_var(xen_vcpu);
  69 }
  70
  71 static void xen_get_wallclock(struct timespec *now)
  72 {
  73         xen_read_wallclock(now);
  74 }
  75
  76 static int xen_set_wallclock(const struct timespec *now)
  77 {
  78         return -1;
  79 }
  80
  81 static int xen_pvclock_gtod_notify(struct notifier_block *nb,
  82                                    unsigned long was_set, void *priv)
  83 {
  84         /* Protected by the calling core code serialization */
  85         static struct timespec64 next_sync;
  86
  87         struct xen_platform_op op;
  88         struct timespec64 now;
  89         struct timekeeper *tk = priv;
  90         static bool settime64_supported = true;
  91         int ret;
  92
  93         now.tv_sec = tk->xtime_sec;
  94         now.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
  95
  96         /*
  97          * We only take the expensive HV call when the clock was set
  98          * or when the 11 minutes RTC synchronization time elapsed.
  99          */
 100         if (!was_set && timespec64_compare(&now, &next_sync) < 0)
 101                 return NOTIFY_OK;
 102
 103 again:
 104         if (settime64_supported) {
 105                 op.cmd = XENPF_settime64;
 106                 op.u.settime64.mbz = 0;
 107                 op.u.settime64.secs = now.tv_sec;
 108                 op.u.settime64.nsecs = now.tv_nsec;
 109                 op.u.settime64.system_time = xen_clocksource_read();
 110         } else {
 111                 op.cmd = XENPF_settime32;
 112                 op.u.settime32.secs = now.tv_sec;
 113                 op.u.settime32.nsecs = now.tv_nsec;
 114                 op.u.settime32.system_time = xen_clocksource_read();
 115         }
 116
 117         ret = HYPERVISOR_platform_op(&op);
 118
 119         if (ret == -ENOSYS && settime64_supported) {
 120                 settime64_supported = false;
 121                 goto again;
 122         }
 123         if (ret < 0)
 124                 return NOTIFY_BAD;
 125
 126         /*
 127          * Move the next drift compensation time 11 minutes
 128          * ahead. That's emulating the sync_cmos_clock() update for
 129          * the hardware RTC.
 130          */
 131         next_sync = now;
 132         next_sync.tv_sec += 11 * 60;
 133
 134         return NOTIFY_OK;
 135 }
 136
 137 static struct notifier_block xen_pvclock_gtod_notifier = {
 138         .notifier_call = xen_pvclock_gtod_notify,
 139 };
 140
 141 static struct clocksource xen_clocksource __read_mostly = {
 142         .name = "xen",
 143         .rating = 400,
 144         .read = xen_clocksource_get_cycles,
 145         .mask = ~0,
 146         .flags = CLOCK_SOURCE_IS_CONTINUOUS,
 147 };
 148
 149 /*
 150    Xen clockevent implementation
 151
 152    Xen has two clockevent implementations:
 153
 154    The old timer_op one works with all released versions of Xen prior
 155    to version 3.0.4.  This version of the hypervisor provides a
 156    single-shot timer with nanosecond resolution.  However, sharing the
 157    same event channel is a 100Hz tick which is delivered while the
 158    vcpu is running.  We don't care about or use this tick, but it will
 159    cause the core time code to think the timer fired too soon, and
 160    will end up resetting it each time.  It could be filtered, but
 161    doing so has complications when the ktime clocksource is not yet
 162    the xen clocksource (ie, at boot time).
 163
 164    The new vcpu_op-based timer interface allows the tick timer period
 165    to be changed or turned off.  The tick timer is not useful as a
 166    periodic timer because events are only delivered to running vcpus.
 167    The one-shot timer can report when a timeout is in the past, so
 168    set_next_event is capable of returning -ETIME when appropriate.
 169    This interface is used when available.
 170 */
 171
 172
 173 /*
 174   Get a hypervisor absolute time.  In theory we could maintain an
 175   offset between the kernel's time and the hypervisor's time, and
 176   apply that to a kernel's absolute timeout.  Unfortunately the
 177   hypervisor and kernel times can drift even if the kernel is using
 178   the Xen clocksource, because ntp can warp the kernel's clocksource.
 179 */
 180 static s64 get_abs_timeout(unsigned long delta)
 181 {
 182         return xen_clocksource_read() + delta;
 183 }
 184
 185 static int xen_timerop_shutdown(struct clock_event_device *evt)
 186 {
 187         /* cancel timeout */
 188         HYPERVISOR_set_timer_op(0);
 189
 190         return 0;
 191 }
 192
 193 static int xen_timerop_set_next_event(unsigned long delta,
 194                                       struct clock_event_device *evt)
 195 {
 196         WARN_ON(!clockevent_state_oneshot(evt));
 197
 198         if (HYPERVISOR_set_timer_op(get_abs_timeout(delta)) < 0)
 199                 BUG();
 200
 201         /* We may have missed the deadline, but there's no real way of
 202            knowing for sure.  If the event was in the past, then we'll
 203            get an immediate interrupt. */
 204
 205         return 0;
 206 }
 207
 208 static const struct clock_event_device xen_timerop_clockevent = {
 209         .name                   = "xen",
 210         .features               = CLOCK_EVT_FEAT_ONESHOT,
 211
 212         .max_delta_ns           = 0xffffffff,
 213         .max_delta_ticks        = 0xffffffff,
 214         .min_delta_ns           = TIMER_SLOP,
 215         .min_delta_ticks        = TIMER_SLOP,
 216
 217         .mult                   = 1,
 218         .shift                  = 0,
 219         .rating                 = 500,
 220
 221         .set_state_shutdown     = xen_timerop_shutdown,
 222         .set_next_event         = xen_timerop_set_next_event,
 223 };
 224
 225 static int xen_vcpuop_shutdown(struct clock_event_device *evt)
 226 {
 227         int cpu = smp_processor_id();
 228
 229         if (HYPERVISOR_vcpu_op(VCPUOP_stop_singleshot_timer, xen_vcpu_nr(cpu),
 230                                NULL) ||
 231             HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, xen_vcpu_nr(cpu),
 232                                NULL))
 233                 BUG();
 234
 235         return 0;
 236 }
 237
 238 static int xen_vcpuop_set_oneshot(struct clock_event_device *evt)
 239 {
 240         int cpu = smp_processor_id();
 241
 242         if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, xen_vcpu_nr(cpu),
 243                                NULL))
 244                 BUG();
 245
 246         return 0;
 247 }
 248
 249 static int xen_vcpuop_set_next_event(unsigned long delta,
 250                                      struct clock_event_device *evt)
 251 {
 252         int cpu = smp_processor_id();
 253         struct vcpu_set_singleshot_timer single;
 254         int ret;
 255
 256         WARN_ON(!clockevent_state_oneshot(evt));
 257
 258         single.timeout_abs_ns = get_abs_timeout(delta);
 259         /* Get an event anyway, even if the timeout is already expired */
 260         single.flags = 0;
 261
 262         ret = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, xen_vcpu_nr(cpu),
 263                                  &single);
 264         BUG_ON(ret != 0);
 265
 266         return ret;
 267 }
 268
 269 static const struct clock_event_device xen_vcpuop_clockevent = {
 270         .name = "xen",
 271         .features = CLOCK_EVT_FEAT_ONESHOT,
 272
 273         .max_delta_ns = 0xffffffff,
 274         .max_delta_ticks = 0xffffffff,
 275         .min_delta_ns = TIMER_SLOP,
 276         .min_delta_ticks = TIMER_SLOP,
 277
 278         .mult = 1,
 279         .shift = 0,
 280         .rating = 500,
 281
 282         .set_state_shutdown = xen_vcpuop_shutdown,
 283         .set_state_oneshot = xen_vcpuop_set_oneshot,
 284         .set_next_event = xen_vcpuop_set_next_event,
 285 };
 286
 287 static const struct clock_event_device *xen_clockevent =
 288         &xen_timerop_clockevent;
 289
 290 struct xen_clock_event_device {
 291         struct clock_event_device evt;
 292         char name[16];
 293 };
 294 static DEFINE_PER_CPU(struct xen_clock_event_device, xen_clock_events) = { .evt.irq = -1 };
 295
 296 static irqreturn_t xen_timer_interrupt(int irq, void *dev_id)
 297 {
 298         struct clock_event_device *evt = this_cpu_ptr(&xen_clock_events.evt);
 299         irqreturn_t ret;
 300
 301         ret = IRQ_NONE;
 302         if (evt->event_handler) {
 303                 evt->event_handler(evt);
 304                 ret = IRQ_HANDLED;
 305         }
 306
 307         return ret;
 308 }
 309
 310 void xen_teardown_timer(int cpu)
 311 {
 312         struct clock_event_device *evt;
 313         evt = &per_cpu(xen_clock_events, cpu).evt;
 314
 315         if (evt->irq >= 0) {
 316                 unbind_from_irqhandler(evt->irq, NULL);
 317                 evt->irq = -1;
 318         }
 319 }
 320
 321 void xen_setup_timer(int cpu)
 322 {
 323         struct xen_clock_event_device *xevt = &per_cpu(xen_clock_events, cpu);
 324         struct clock_event_device *evt = &xevt->evt;
 325         int irq;
 326
 327         WARN(evt->irq >= 0, "IRQ%d for CPU%d is already allocated\n", evt->irq, cpu);
 328         if (evt->irq >= 0)
 329                 xen_teardown_timer(cpu);
 330
 331         printk(KERN_INFO "installing Xen timer for CPU %d\n", cpu);
 332
 333         snprintf(xevt->name, sizeof(xevt->name), "timer%d", cpu);
 334
 335         irq = bind_virq_to_irqhandler(VIRQ_TIMER, cpu, xen_timer_interrupt,
 336                                       IRQF_PERCPU|IRQF_NOBALANCING|IRQF_TIMER|
 337                                       IRQF_FORCE_RESUME|IRQF_EARLY_RESUME,
 338                                       xevt->name, NULL);
 339         (void)xen_set_irq_priority(irq, XEN_IRQ_PRIORITY_MAX);
 340
 341         memcpy(evt, xen_clockevent, sizeof(*evt));
 342
 343         evt->cpumask = cpumask_of(cpu);
 344         evt->irq = irq;
 345 }
 346
 347
 348 void xen_setup_cpu_clockevents(void)
 349 {
 350         clockevents_register_device(this_cpu_ptr(&xen_clock_events.evt));
 351 }
 352
 353 void xen_timer_resume(void)
 354 {
 355         int cpu;
 356
 357         pvclock_resume();
 358
 359         if (xen_clockevent != &xen_vcpuop_clockevent)
 360                 return;
 361
 362         for_each_online_cpu(cpu) {
 363                 if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer,
 364                                        xen_vcpu_nr(cpu), NULL))
 365                         BUG();
 366         }
 367 }
 368
 369 static const struct pv_time_ops xen_time_ops __initconst = {
 370         .sched_clock = xen_clocksource_read,
 371         .steal_clock = xen_steal_clock,
 372 };
 373
 374 static void __init xen_time_init(void)
 375 {
 376         int cpu = smp_processor_id();
 377         struct timespec tp;
 378
 379         /* As Dom0 is never moved, no penalty on using TSC there */
 380         if (xen_initial_domain())
 381                 xen_clocksource.rating = 275;
 382
 383         clocksource_register_hz(&xen_clocksource, NSEC_PER_SEC);
 384
 385         if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, xen_vcpu_nr(cpu),
 386                                NULL) == 0) {
 387                 /* Successfully turned off 100Hz tick, so we have the
 388                    vcpuop-based timer interface */
 389                 printk(KERN_DEBUG "Xen: using vcpuop timer interface\n");
 390                 xen_clockevent = &xen_vcpuop_clockevent;
 391         }
 392
 393         /* Set initial system time with full resolution */
 394         xen_read_wallclock(&tp);
 395         do_settimeofday(&tp);
 396
 397         setup_force_cpu_cap(X86_FEATURE_TSC);
 398
 399         xen_setup_runstate_info(cpu);
 400         xen_setup_timer(cpu);
 401         xen_setup_cpu_clockevents();
 402
 403         xen_time_setup_guest();
 404
 405         if (xen_initial_domain())
 406                 pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
 407 }
 408
 409 void __ref xen_init_time_ops(void)
 410 {
 411         pv_time_ops = xen_time_ops;
 412
 413         x86_init.timers.timer_init = xen_time_init;
 414         x86_init.timers.setup_percpu_clockev = x86_init_noop;
 415         x86_cpuinit.setup_percpu_clockev = x86_init_noop;
 416
 417         x86_platform.calibrate_tsc = xen_tsc_khz;
 418         x86_platform.get_wallclock = xen_get_wallclock;
 419         /* Dom0 uses the native method to set the hardware RTC. */
 420         if (!xen_initial_domain())
 421                 x86_platform.set_wallclock = xen_set_wallclock;
 422 }
 423
 424 #ifdef CONFIG_XEN_PVHVM
 425 static void xen_hvm_setup_cpu_clockevents(void)
 426 {
 427         int cpu = smp_processor_id();
 428         xen_setup_runstate_info(cpu);
 429         /*
 430          * xen_setup_timer(cpu) - snprintf is bad in atomic context. Hence
 431          * doing it xen_hvm_cpu_notify (which gets called by smp_init during
 432          * early bootup and also during CPU hotplug events).
 433          */
 434         xen_setup_cpu_clockevents();
 435 }
 436
 437 void __init xen_hvm_init_time_ops(void)
 438 {
 439         /*
 440          * vector callback is needed otherwise we cannot receive interrupts
 441          * on cpu > 0 and at this point we don't know how many cpus are
 442          * available.
 443          */
 444         if (!xen_have_vector_callback)
 445                 return;
 446
 447         if (!xen_feature(XENFEAT_hvm_safe_pvclock)) {
 448                 printk(KERN_INFO "Xen doesn't support pvclock on HVM,"
 449                                 "disable pv timer\n");
 450                 return;
 451         }
 452
 453         pv_time_ops = xen_time_ops;
 454         x86_init.timers.setup_percpu_clockev = xen_time_init;
 455         x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents;
 456
 457         x86_platform.calibrate_tsc = xen_tsc_khz;
 458         x86_platform.get_wallclock = xen_get_wallclock;
 459         x86_platform.set_wallclock = xen_set_wallclock;
 460 }
 461 #endif