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 #include <asm/xen/cpuid.h>
24
25 #include <xen/events.h>
26 #include <xen/features.h>
27 #include <xen/interface/xen.h>
28 #include <xen/interface/vcpu.h>
29
30 #include "xen-ops.h"
31
32 /* Minimum amount of time until next clock event fires */
33 #define TIMER_SLOP 1
34
35 static u64 xen_sched_clock_offset __read_mostly;
36
37 /* Get the TSC speed from Xen */
38 static unsigned long xen_tsc_khz(void)
39 {
40 struct pvclock_vcpu_time_info *info =
41 &HYPERVISOR_shared_info->vcpu_info[0].time;
42
43 setup_force_cpu_cap(X86_FEATURE_TSC_KNOWN_FREQ);
44 return pvclock_tsc_khz(info);
45 }
46
47 static u64 xen_clocksource_read(void)
48 {
49 struct pvclock_vcpu_time_info *src;
50 u64 ret;
51
52 preempt_disable_notrace();
53 src = &__this_cpu_read(xen_vcpu)->time;
54 ret = pvclock_clocksource_read(src);
55 preempt_enable_notrace();
56 return ret;
57 }
58
59 static u64 xen_clocksource_get_cycles(struct clocksource *cs)
60 {
61 return xen_clocksource_read();
62 }
63
64 static noinstr u64 xen_sched_clock(void)
65 {
66 struct pvclock_vcpu_time_info *src;
67 u64 ret;
68
69 src = &__this_cpu_read(xen_vcpu)->time;
70 ret = pvclock_clocksource_read_nowd(src);
71 ret -= xen_sched_clock_offset;
72
73 return ret;
74 }
75
76 static void xen_read_wallclock(struct timespec64 *ts)
77 {
78 struct shared_info *s = HYPERVISOR_shared_info;
79 struct pvclock_wall_clock *wall_clock = &(s->wc);
80 struct pvclock_vcpu_time_info *vcpu_time;
81
82 vcpu_time = &get_cpu_var(xen_vcpu)->time;
83 pvclock_read_wallclock(wall_clock, vcpu_time, ts);
84 put_cpu_var(xen_vcpu);
85 }
86
87 static void xen_get_wallclock(struct timespec64 *now)
88 {
89 xen_read_wallclock(now);
90 }
91
92 static int xen_set_wallclock(const struct timespec64 *now)
93 {
94 return -ENODEV;
95 }
96
97 static int xen_pvclock_gtod_notify(struct notifier_block *nb,
98 unsigned long was_set, void *priv)
99 {
100 /* Protected by the calling core code serialization */
101 static struct timespec64 next_sync;
102
103 struct xen_platform_op op;
104 struct timespec64 now;
105 struct timekeeper *tk = priv;
106 static bool settime64_supported = true;
107 int ret;
108
109 now.tv_sec = tk->xtime_sec;
110 now.tv_nsec = (long)(tk->tkr_mono.xtime_nsec >> tk->tkr_mono.shift);
111
112 /*
113 * We only take the expensive HV call when the clock was set
114 * or when the 11 minutes RTC synchronization time elapsed.
115 */
116 if (!was_set && timespec64_compare(&now, &next_sync) < 0)
117 return NOTIFY_OK;
118
119 again:
120 if (settime64_supported) {
121 op.cmd = XENPF_settime64;
122 op.u.settime64.mbz = 0;
123 op.u.settime64.secs = now.tv_sec;
124 op.u.settime64.nsecs = now.tv_nsec;
125 op.u.settime64.system_time = xen_clocksource_read();
126 } else {
127 op.cmd = XENPF_settime32;
128 op.u.settime32.secs = now.tv_sec;
129 op.u.settime32.nsecs = now.tv_nsec;
130 op.u.settime32.system_time = xen_clocksource_read();
131 }
132
133 ret = HYPERVISOR_platform_op(&op);
134
135 if (ret == -ENOSYS && settime64_supported) {
136 settime64_supported = false;
137 goto again;
138 }
139 if (ret < 0)
140 return NOTIFY_BAD;
141
142 /*
143 * Move the next drift compensation time 11 minutes
144 * ahead. That's emulating the sync_cmos_clock() update for
145 * the hardware RTC.
146 */
147 next_sync = now;
148 next_sync.tv_sec += 11 * 60;
149
150 return NOTIFY_OK;
151 }
152
153 static struct notifier_block xen_pvclock_gtod_notifier = {
154 .notifier_call = xen_pvclock_gtod_notify,
155 };
156
157 static int xen_cs_enable(struct clocksource *cs)
158 {
159 vclocks_set_used(VDSO_CLOCKMODE_PVCLOCK);
160 return 0;
161 }
162
163 static struct clocksource xen_clocksource __read_mostly = {
164 .name = "xen",
165 .rating = 400,
166 .read = xen_clocksource_get_cycles,
167 .mask = CLOCKSOURCE_MASK(64),
168 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
169 .enable = xen_cs_enable,
170 };
171
172 /*
173 Xen clockevent implementation
174
175 Xen has two clockevent implementations:
176
177 The old timer_op one works with all released versions of Xen prior
178 to version 3.0.4. This version of the hypervisor provides a
179 single-shot timer with nanosecond resolution. However, sharing the
180 same event channel is a 100Hz tick which is delivered while the
181 vcpu is running. We don't care about or use this tick, but it will
182 cause the core time code to think the timer fired too soon, and
183 will end up resetting it each time. It could be filtered, but
184 doing so has complications when the ktime clocksource is not yet
185 the xen clocksource (ie, at boot time).
186
187 The new vcpu_op-based timer interface allows the tick timer period
188 to be changed or turned off. The tick timer is not useful as a
189 periodic timer because events are only delivered to running vcpus.
190 The one-shot timer can report when a timeout is in the past, so
191 set_next_event is capable of returning -ETIME when appropriate.
192 This interface is used when available.
193 */
194
195
196 /*
197 Get a hypervisor absolute time. In theory we could maintain an
198 offset between the kernel's time and the hypervisor's time, and
199 apply that to a kernel's absolute timeout. Unfortunately the
200 hypervisor and kernel times can drift even if the kernel is using
201 the Xen clocksource, because ntp can warp the kernel's clocksource.
202 */
203 static s64 get_abs_timeout(unsigned long delta)
204 {
205 return xen_clocksource_read() + delta;
206 }
207
208 static int xen_timerop_shutdown(struct clock_event_device *evt)
209 {
210 /* cancel timeout */
211 HYPERVISOR_set_timer_op(0);
212
213 return 0;
214 }
215
216 static int xen_timerop_set_next_event(unsigned long delta,
217 struct clock_event_device *evt)
218 {
219 WARN_ON(!clockevent_state_oneshot(evt));
220
221 if (HYPERVISOR_set_timer_op(get_abs_timeout(delta)) < 0)
222 BUG();
223
224 /* We may have missed the deadline, but there's no real way of
225 knowing for sure. If the event was in the past, then we'll
226 get an immediate interrupt. */
227
228 return 0;
229 }
230
231 static struct clock_event_device xen_timerop_clockevent __ro_after_init = {
232 .name = "xen",
233 .features = CLOCK_EVT_FEAT_ONESHOT,
234
235 .max_delta_ns = 0xffffffff,
236 .max_delta_ticks = 0xffffffff,
237 .min_delta_ns = TIMER_SLOP,
238 .min_delta_ticks = TIMER_SLOP,
239
240 .mult = 1,
241 .shift = 0,
242 .rating = 500,
243
244 .set_state_shutdown = xen_timerop_shutdown,
245 .set_next_event = xen_timerop_set_next_event,
246 };
247
248 static int xen_vcpuop_shutdown(struct clock_event_device *evt)
249 {
250 int cpu = smp_processor_id();
251
252 if (HYPERVISOR_vcpu_op(VCPUOP_stop_singleshot_timer, xen_vcpu_nr(cpu),
253 NULL) ||
254 HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, xen_vcpu_nr(cpu),
255 NULL))
256 BUG();
257
258 return 0;
259 }
260
261 static int xen_vcpuop_set_oneshot(struct clock_event_device *evt)
262 {
263 int cpu = smp_processor_id();
264
265 if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, xen_vcpu_nr(cpu),
266 NULL))
267 BUG();
268
269 return 0;
270 }
271
272 static int xen_vcpuop_set_next_event(unsigned long delta,
273 struct clock_event_device *evt)
274 {
275 int cpu = smp_processor_id();
276 struct vcpu_set_singleshot_timer single;
277 int ret;
278
279 WARN_ON(!clockevent_state_oneshot(evt));
280
281 single.timeout_abs_ns = get_abs_timeout(delta);
282 /* Get an event anyway, even if the timeout is already expired */
283 single.flags = 0;
284
285 ret = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, xen_vcpu_nr(cpu),
286 &single);
287 BUG_ON(ret != 0);
288
289 return ret;
290 }
291
292 static struct clock_event_device xen_vcpuop_clockevent __ro_after_init = {
293 .name = "xen",
294 .features = CLOCK_EVT_FEAT_ONESHOT,
295
296 .max_delta_ns = 0xffffffff,
297 .max_delta_ticks = 0xffffffff,
298 .min_delta_ns = TIMER_SLOP,
299 .min_delta_ticks = TIMER_SLOP,
300
301 .mult = 1,
302 .shift = 0,
303 .rating = 500,
304
305 .set_state_shutdown = xen_vcpuop_shutdown,
306 .set_state_oneshot = xen_vcpuop_set_oneshot,
307 .set_next_event = xen_vcpuop_set_next_event,
308 };
309
310 static const struct clock_event_device *xen_clockevent =
311 &xen_timerop_clockevent;
312
313 struct xen_clock_event_device {
314 struct clock_event_device evt;
315 char name[16];
316 };
317 static DEFINE_PER_CPU(struct xen_clock_event_device, xen_clock_events) = { .evt.irq = -1 };
318
319 static irqreturn_t xen_timer_interrupt(int irq, void *dev_id)
320 {
321 struct clock_event_device *evt = this_cpu_ptr(&xen_clock_events.evt);
322 irqreturn_t ret;
323
324 ret = IRQ_NONE;
325 if (evt->event_handler) {
326 evt->event_handler(evt);
327 ret = IRQ_HANDLED;
328 }
329
330 return ret;
331 }
332
333 void xen_teardown_timer(int cpu)
334 {
335 struct clock_event_device *evt;
336 evt = &per_cpu(xen_clock_events, cpu).evt;
337
338 if (evt->irq >= 0) {
339 unbind_from_irqhandler(evt->irq, NULL);
340 evt->irq = -1;
341 }
342 }
343
344 void xen_setup_timer(int cpu)
345 {
346 struct xen_clock_event_device *xevt = &per_cpu(xen_clock_events, cpu);
347 struct clock_event_device *evt = &xevt->evt;
348 int irq;
349
350 WARN(evt->irq >= 0, "IRQ%d for CPU%d is already allocated\n", evt->irq, cpu);
351 if (evt->irq >= 0)
352 xen_teardown_timer(cpu);
353
354 printk(KERN_INFO "installing Xen timer for CPU %d\n", cpu);
355
356 snprintf(xevt->name, sizeof(xevt->name), "timer%d", cpu);
357
358 irq = bind_virq_to_irqhandler(VIRQ_TIMER, cpu, xen_timer_interrupt,
359 IRQF_PERCPU|IRQF_NOBALANCING|IRQF_TIMER|
360 IRQF_FORCE_RESUME|IRQF_EARLY_RESUME,
361 xevt->name, NULL);
362 (void)xen_set_irq_priority(irq, XEN_IRQ_PRIORITY_MAX);
363
364 memcpy(evt, xen_clockevent, sizeof(*evt));
365
366 evt->cpumask = cpumask_of(cpu);
367 evt->irq = irq;
368 }
369
370
371 void xen_setup_cpu_clockevents(void)
372 {
373 clockevents_register_device(this_cpu_ptr(&xen_clock_events.evt));
374 }
375
376 void xen_timer_resume(void)
377 {
378 int cpu;
379
380 if (xen_clockevent != &xen_vcpuop_clockevent)
381 return;
382
383 for_each_online_cpu(cpu) {
384 if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer,
385 xen_vcpu_nr(cpu), NULL))
386 BUG();
387 }
388 }
389
390 static struct pvclock_vsyscall_time_info *xen_clock __read_mostly;
391 static u64 xen_clock_value_saved;
392
393 void xen_save_time_memory_area(void)
394 {
395 struct vcpu_register_time_memory_area t;
396 int ret;
397
398 xen_clock_value_saved = xen_clocksource_read() - xen_sched_clock_offset;
399
400 if (!xen_clock)
401 return;
402
403 t.addr.v = NULL;
404
405 ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
406 if (ret != 0)
407 pr_notice("Cannot save secondary vcpu_time_info (err %d)",
408 ret);
409 else
410 clear_page(xen_clock);
411 }
412
413 void xen_restore_time_memory_area(void)
414 {
415 struct vcpu_register_time_memory_area t;
416 int ret;
417
418 if (!xen_clock)
419 goto out;
420
421 t.addr.v = &xen_clock->pvti;
422
423 ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
424
425 /*
426 * We don't disable VDSO_CLOCKMODE_PVCLOCK entirely if it fails to
427 * register the secondary time info with Xen or if we migrated to a
428 * host without the necessary flags. On both of these cases what
429 * happens is either process seeing a zeroed out pvti or seeing no
430 * PVCLOCK_TSC_STABLE_BIT bit set. Userspace checks the latter and
431 * if 0, it discards the data in pvti and fallbacks to a system
432 * call for a reliable timestamp.
433 */
434 if (ret != 0)
435 pr_notice("Cannot restore secondary vcpu_time_info (err %d)",
436 ret);
437
438 out:
439 /* Need pvclock_resume() before using xen_clocksource_read(). */
440 pvclock_resume();
441 xen_sched_clock_offset = xen_clocksource_read() - xen_clock_value_saved;
442 }
443
444 static void xen_setup_vsyscall_time_info(void)
445 {
446 struct vcpu_register_time_memory_area t;
447 struct pvclock_vsyscall_time_info *ti;
448 int ret;
449
450 ti = (struct pvclock_vsyscall_time_info *)get_zeroed_page(GFP_KERNEL);
451 if (!ti)
452 return;
453
454 t.addr.v = &ti->pvti;
455
456 ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area, 0, &t);
457 if (ret) {
458 pr_notice("xen: VDSO_CLOCKMODE_PVCLOCK not supported (err %d)\n", ret);
459 free_page((unsigned long)ti);
460 return;
461 }
462
463 /*
464 * If primary time info had this bit set, secondary should too since
465 * it's the same data on both just different memory regions. But we
466 * still check it in case hypervisor is buggy.
467 */
468 if (!(ti->pvti.flags & PVCLOCK_TSC_STABLE_BIT)) {
469 t.addr.v = NULL;
470 ret = HYPERVISOR_vcpu_op(VCPUOP_register_vcpu_time_memory_area,
471 0, &t);
472 if (!ret)
473 free_page((unsigned long)ti);
474
475 pr_notice("xen: VDSO_CLOCKMODE_PVCLOCK not supported (tsc unstable)\n");
476 return;
477 }
478
479 xen_clock = ti;
480 pvclock_set_pvti_cpu0_va(xen_clock);
481
482 xen_clocksource.vdso_clock_mode = VDSO_CLOCKMODE_PVCLOCK;
483 }
484
485 /*
486 * Check if it is possible to safely use the tsc as a clocksource. This is
487 * only true if the hypervisor notifies the guest that its tsc is invariant,
488 * the tsc is stable, and the tsc instruction will never be emulated.
489 */
490 static int __init xen_tsc_safe_clocksource(void)
491 {
492 u32 eax, ebx, ecx, edx;
493
494 if (!(boot_cpu_has(X86_FEATURE_CONSTANT_TSC)))
495 return 0;
496
497 if (!(boot_cpu_has(X86_FEATURE_NONSTOP_TSC)))
498 return 0;
499
500 if (check_tsc_unstable())
501 return 0;
502
503 /* Leaf 4, sub-leaf 0 (0x40000x03) */
504 cpuid_count(xen_cpuid_base() + 3, 0, &eax, &ebx, &ecx, &edx);
505
506 return ebx == XEN_CPUID_TSC_MODE_NEVER_EMULATE;
507 }
508
509 static void __init xen_time_init(void)
510 {
511 struct pvclock_vcpu_time_info *pvti;
512 int cpu = smp_processor_id();
513 struct timespec64 tp;
514
515 /*
516 * As Dom0 is never moved, no penalty on using TSC there.
517 *
518 * If it is possible for the guest to determine that the tsc is a safe
519 * clocksource, then set xen_clocksource rating below that of the tsc
520 * so that the system prefers tsc instead.
521 */
522 if (xen_initial_domain())
523 xen_clocksource.rating = 275;
524 else if (xen_tsc_safe_clocksource())
525 xen_clocksource.rating = 299;
526
527 clocksource_register_hz(&xen_clocksource, NSEC_PER_SEC);
528
529 if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, xen_vcpu_nr(cpu),
530 NULL) == 0) {
531 /* Successfully turned off 100Hz tick, so we have the
532 vcpuop-based timer interface */
533 printk(KERN_DEBUG "Xen: using vcpuop timer interface\n");
534 xen_clockevent = &xen_vcpuop_clockevent;
535 }
536
537 /* Set initial system time with full resolution */
538 xen_read_wallclock(&tp);
539 do_settimeofday64(&tp);
540
541 setup_force_cpu_cap(X86_FEATURE_TSC);
542
543 /*
544 * We check ahead on the primary time info if this
545 * bit is supported hence speeding up Xen clocksource.
546 */
547 pvti = &__this_cpu_read(xen_vcpu)->time;
548 if (pvti->flags & PVCLOCK_TSC_STABLE_BIT) {
549 pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
550 xen_setup_vsyscall_time_info();
551 }
552
553 xen_setup_runstate_info(cpu);
554 xen_setup_timer(cpu);
555 xen_setup_cpu_clockevents();
556
557 xen_time_setup_guest();
558
559 if (xen_initial_domain())
560 pvclock_gtod_register_notifier(&xen_pvclock_gtod_notifier);
561 }
562
563 static void __init xen_init_time_common(void)
564 {
565 xen_sched_clock_offset = xen_clocksource_read();
566 static_call_update(pv_steal_clock, xen_steal_clock);
567 paravirt_set_sched_clock(xen_sched_clock);
568
569 x86_platform.calibrate_tsc = xen_tsc_khz;
570 x86_platform.get_wallclock = xen_get_wallclock;
571 }
572
573 void __init xen_init_time_ops(void)
574 {
575 xen_init_time_common();
576
577 x86_init.timers.timer_init = xen_time_init;
578 x86_init.timers.setup_percpu_clockev = x86_init_noop;
579 x86_cpuinit.setup_percpu_clockev = x86_init_noop;
580
581 /* Dom0 uses the native method to set the hardware RTC. */
582 if (!xen_initial_domain())
583 x86_platform.set_wallclock = xen_set_wallclock;
584 }
585
586 #ifdef CONFIG_XEN_PVHVM
587 static void xen_hvm_setup_cpu_clockevents(void)
588 {
589 int cpu = smp_processor_id();
590 xen_setup_runstate_info(cpu);
591 /*
592 * xen_setup_timer(cpu) - snprintf is bad in atomic context. Hence
593 * doing it xen_hvm_cpu_notify (which gets called by smp_init during
594 * early bootup and also during CPU hotplug events).
595 */
596 xen_setup_cpu_clockevents();
597 }
598
599 void __init xen_hvm_init_time_ops(void)
600 {
601 static bool hvm_time_initialized;
602
603 if (hvm_time_initialized)
604 return;
605
606 /*
607 * vector callback is needed otherwise we cannot receive interrupts
608 * on cpu > 0 and at this point we don't know how many cpus are
609 * available.
610 */
611 if (!xen_have_vector_callback)
612 return;
613
614 if (!xen_feature(XENFEAT_hvm_safe_pvclock)) {
615 pr_info_once("Xen doesn't support pvclock on HVM, disable pv timer");
616 return;
617 }
618
619 /*
620 * Only MAX_VIRT_CPUS 'vcpu_info' are embedded inside 'shared_info'.
621 * The __this_cpu_read(xen_vcpu) is still NULL when Xen HVM guest
622 * boots on vcpu >= MAX_VIRT_CPUS (e.g., kexec), To access
623 * __this_cpu_read(xen_vcpu) via xen_clocksource_read() will panic.
624 *
625 * The xen_hvm_init_time_ops() should be called again later after
626 * __this_cpu_read(xen_vcpu) is available.
627 */
628 if (!__this_cpu_read(xen_vcpu)) {
629 pr_info("Delay xen_init_time_common() as kernel is running on vcpu=%d\n",
630 xen_vcpu_nr(0));
631 return;
632 }
633
634 xen_init_time_common();
635
636 x86_init.timers.setup_percpu_clockev = xen_time_init;
637 x86_cpuinit.setup_percpu_clockev = xen_hvm_setup_cpu_clockevents;
638
639 x86_platform.set_wallclock = xen_set_wallclock;
640
641 hvm_time_initialized = true;
642 }
643 #endif
644
645 /* Kernel parameter to specify Xen timer slop */
646 static int __init parse_xen_timer_slop(char *ptr)
647 {
648 unsigned long slop = memparse(ptr, NULL);
649
650 xen_timerop_clockevent.min_delta_ns = slop;
651 xen_timerop_clockevent.min_delta_ticks = slop;
652 xen_vcpuop_clockevent.min_delta_ns = slop;
653 xen_vcpuop_clockevent.min_delta_ticks = slop;
654
655 return 0;
656 }
657 early_param("xen_timer_slop", parse_xen_timer_slop);
658
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