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Linux/arch/x86/xen/time.c

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  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 timespec64 *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 timespec64 *now)
 72 {
 73         xen_read_wallclock(now);
 74 }
 75 
 76 static int xen_set_wallclock(const struct timespec64 *now)
 77 {
 78         return -ENODEV;
 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 struct pvclock_vsyscall_time_info *xen_clock __read_mostly;
375 
376 void xen_save_time_memory_area(void)
377 {
378         struct vcpu_register_time_memory_area t;
379         int ret;
380 
381         if (!xen_clock)
382                 return;
383 
384         t.addr.v = NULL;
385 
386         ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
387         if (ret != 0)
388                 pr_notice("Cannot save secondary vcpu_time_info (err %d)",
389                           ret);
390         else
391                 clear_page(xen_clock);
392 }
393 
394 void xen_restore_time_memory_area(void)
395 {
396         struct vcpu_register_time_memory_area t;
397         int ret;
398 
399         if (!xen_clock)
400                 return;
401 
402         t.addr.v = &xen_clock->pvti;
403 
404         ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
405 
406         /*
407          * We don't disable VCLOCK_PVCLOCK entirely if it fails to register the
408          * secondary time info with Xen or if we migrated to a host without the
409          * necessary flags. On both of these cases what happens is either
410          * process seeing a zeroed out pvti or seeing no PVCLOCK_TSC_STABLE_BIT
411          * bit set. Userspace checks the latter and if 0, it discards the data
412          * in pvti and fallbacks to a system call for a reliable timestamp.
413          */
414         if (ret != 0)
415                 pr_notice("Cannot restore secondary vcpu_time_info (err %d)",
416                           ret);
417 }
418 
419 static void xen_setup_vsyscall_time_info(void)
420 {
421         struct vcpu_register_time_memory_area t;
422         struct pvclock_vsyscall_time_info *ti;
423         int ret;
424 
425         ti = (struct pvclock_vsyscall_time_info *)get_zeroed_page(GFP_KERNEL);
426         if (!ti)
427                 return;
428 
429         t.addr.v = &ti->pvti;
430 
431         ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
432         if (ret) {
433                 pr_notice("xen: VCLOCK_PVCLOCK not supported (err %d)\n", ret);
434                 free_page((unsigned long)ti);
435                 return;
436         }
437 
438         /*
439          * If primary time info had this bit set, secondary should too since
440          * it's the same data on both just different memory regions. But we
441          * still check it in case hypervisor is buggy.
442          */
443         if (!(ti->pvti.flags & PVCLOCK_TSC_STABLE_BIT)) {
444                 t.addr.v = NULL;
445                 ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area,
446                                          0, &t);
447                 if (!ret)
448                         free_page((unsigned long)ti);
449 
450                 pr_notice("xen: VCLOCK_PVCLOCK not supported (tsc unstable)\n");
451                 return;
452         }
453 
454         xen_clock = ti;
455         pvclock_set_pvti_cpu0_va(xen_clock);
456 
457         xen_clocksource.archdata.vclock_mode = VCLOCK_PVCLOCK;
458 }
459 
460 static void __init xen_time_init(void)
461 {
462         struct pvclock_vcpu_time_info *pvti;
463         int cpu = smp_processor_id();
464         struct timespec64 tp;
465 
466         /* As Dom0 is never moved, no penalty on using TSC there */
467         if (xen_initial_domain())
468                 xen_clocksource.rating = 275;
469 
470         clocksource_register_hz(&xen_clocksource, NSEC_PER_SEC);
471 
472         if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, xen_vcpu_nr(cpu),
473                                NULL) == 0) {
474                 /* Successfully turned off 100Hz tick, so we have the
475                    vcpuop-based timer interface */
476                 printk(KERN_DEBUG "Xen: using vcpuop timer interface\n");
477                 xen_clockevent = &xen_vcpuop_clockevent;
478         }
479 
480         /* Set initial system time with full resolution */
481         xen_read_wallclock(&tp);
482         do_settimeofday64(&tp);
483 
484         setup_force_cpu_cap(X86_FEATURE_TSC);
485 
486         /*
487          * We check ahead on the primary time info if this
488          * bit is supported hence speeding up Xen clocksource.
489          */
490         pvti = &__this_cpu_read(xen_vcpu)->time;
491         if (pvti->flags & PVCLOCK_TSC_STABLE_BIT) {
492                 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
493                 xen_setup_vsyscall_time_info();
494         }
495 
496         xen_setup_runstate_info(cpu);
497         xen_setup_timer(cpu);
498         xen_setup_cpu_clockevents();
499 
500         xen_time_setup_guest();
501 
502         if (xen_initial_domain())
503                 pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
504 }
505 
506 void __ref xen_init_time_ops(void)
507 {
508         pv_time_ops = xen_time_ops;
509 
510         x86_init.timers.timer_init = xen_time_init;
511         x86_init.timers.setup_percpu_clockev = x86_init_noop;
512         x86_cpuinit.setup_percpu_clockev = x86_init_noop;
513 
514         x86_platform.calibrate_tsc = xen_tsc_khz;
515         x86_platform.get_wallclock = xen_get_wallclock;
516         /* Dom0 uses the native method to set the hardware RTC. */
517         if (!xen_initial_domain())
518                 x86_platform.set_wallclock = xen_set_wallclock;
519 }
520 
521 #ifdef CONFIG_XEN_PVHVM
522 static void xen_hvm_setup_cpu_clockevents(void)
523 {
524         int cpu = smp_processor_id();
525         xen_setup_runstate_info(cpu);
526         /*
527          * xen_setup_timer(cpu) - snprintf is bad in atomic context. Hence
528          * doing it xen_hvm_cpu_notify (which gets called by smp_init during
529          * early bootup and also during CPU hotplug events).
530          */
531         xen_setup_cpu_clockevents();
532 }
533 
534 void __init xen_hvm_init_time_ops(void)
535 {
536         /*
537          * vector callback is needed otherwise we cannot receive interrupts
538          * on cpu > 0 and at this point we don't know how many cpus are
539          * available.
540          */
541         if (!xen_have_vector_callback)
542                 return;
543 
544         if (!xen_feature(XENFEAT_hvm_safe_pvclock)) {
545                 printk(KERN_INFO "Xen doesn't support pvclock on HVM,"
546                                 "disable pv timer\n");
547                 return;
548         }
549 
550         pv_time_ops = xen_time_ops;
551         x86_init.timers.setup_percpu_clockev = xen_time_init;
552         x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents;
553 
554         x86_platform.calibrate_tsc = xen_tsc_khz;
555         x86_platform.get_wallclock = xen_get_wallclock;
556         x86_platform.set_wallclock = xen_set_wallclock;
557 }
558 #endif
559 

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