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15c84731
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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>
f91a8b44 14#include <linux/kernel_stat.h>
f595ec96 15#include <linux/math64.h>
15c84731 16
1c7b67f7 17#include <asm/pvclock.h>
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18#include <asm/xen/hypervisor.h>
19#include <asm/xen/hypercall.h>
20
21#include <xen/events.h>
22#include <xen/interface/xen.h>
23#include <xen/interface/vcpu.h>
24
25#include "xen-ops.h"
26
27#define XEN_SHIFT 22
28
29/* Xen may fire a timer up to this many ns early */
30#define TIMER_SLOP 100000
f91a8b44 31#define NS_PER_TICK (1000000000LL / HZ)
15c84731 32
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33/* runstate info updated by Xen */
34static DEFINE_PER_CPU(struct vcpu_runstate_info, runstate);
35
36/* snapshots of runstate info */
37static DEFINE_PER_CPU(struct vcpu_runstate_info, runstate_snapshot);
38
39/* unused ns of stolen and blocked time */
40static DEFINE_PER_CPU(u64, residual_stolen);
41static DEFINE_PER_CPU(u64, residual_blocked);
42
43/* return an consistent snapshot of 64-bit time/counter value */
44static u64 get64(const u64 *p)
45{
46 u64 ret;
47
48 if (BITS_PER_LONG < 64) {
49 u32 *p32 = (u32 *)p;
50 u32 h, l;
51
52 /*
53 * Read high then low, and then make sure high is
54 * still the same; this will only loop if low wraps
55 * and carries into high.
56 * XXX some clean way to make this endian-proof?
57 */
58 do {
59 h = p32[1];
60 barrier();
61 l = p32[0];
62 barrier();
63 } while (p32[1] != h);
64
65 ret = (((u64)h) << 32) | l;
66 } else
67 ret = *p;
68
69 return ret;
70}
71
72/*
73 * Runstate accounting
74 */
75static void get_runstate_snapshot(struct vcpu_runstate_info *res)
76{
77 u64 state_time;
78 struct vcpu_runstate_info *state;
79
f120f13e 80 BUG_ON(preemptible());
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81
82 state = &__get_cpu_var(runstate);
83
84 /*
85 * The runstate info is always updated by the hypervisor on
86 * the current CPU, so there's no need to use anything
87 * stronger than a compiler barrier when fetching it.
88 */
89 do {
90 state_time = get64(&state->state_entry_time);
91 barrier();
92 *res = *state;
93 barrier();
94 } while (get64(&state->state_entry_time) != state_time);
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95}
96
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97/* return true when a vcpu could run but has no real cpu to run on */
98bool xen_vcpu_stolen(int vcpu)
99{
100 return per_cpu(runstate, vcpu).state == RUNSTATE_runnable;
101}
102
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103static void setup_runstate_info(int cpu)
104{
105 struct vcpu_register_runstate_memory_area area;
106
107 area.addr.v = &per_cpu(runstate, cpu);
108
109 if (HYPERVISOR_vcpu_op(VCPUOP_register_runstate_memory_area,
110 cpu, &area))
111 BUG();
112}
113
114static void do_stolen_accounting(void)
115{
116 struct vcpu_runstate_info state;
117 struct vcpu_runstate_info *snap;
118 s64 blocked, runnable, offline, stolen;
119 cputime_t ticks;
120
121 get_runstate_snapshot(&state);
122
123 WARN_ON(state.state != RUNSTATE_running);
124
125 snap = &__get_cpu_var(runstate_snapshot);
126
127 /* work out how much time the VCPU has not been runn*ing* */
128 blocked = state.time[RUNSTATE_blocked] - snap->time[RUNSTATE_blocked];
129 runnable = state.time[RUNSTATE_runnable] - snap->time[RUNSTATE_runnable];
130 offline = state.time[RUNSTATE_offline] - snap->time[RUNSTATE_offline];
131
132 *snap = state;
133
134 /* Add the appropriate number of ticks of stolen time,
79741dd3 135 including any left-overs from last time. */
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136 stolen = runnable + offline + __get_cpu_var(residual_stolen);
137
138 if (stolen < 0)
139 stolen = 0;
140
f595ec96 141 ticks = iter_div_u64_rem(stolen, NS_PER_TICK, &stolen);
f91a8b44 142 __get_cpu_var(residual_stolen) = stolen;
79741dd3 143 account_steal_ticks(ticks);
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144
145 /* Add the appropriate number of ticks of blocked time,
79741dd3 146 including any left-overs from last time. */
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147 blocked += __get_cpu_var(residual_blocked);
148
149 if (blocked < 0)
150 blocked = 0;
151
f595ec96 152 ticks = iter_div_u64_rem(blocked, NS_PER_TICK, &blocked);
f91a8b44 153 __get_cpu_var(residual_blocked) = blocked;
79741dd3 154 account_idle_ticks(ticks);
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155}
156
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157/*
158 * Xen sched_clock implementation. Returns the number of unstolen
159 * nanoseconds, which is nanoseconds the VCPU spent in RUNNING+BLOCKED
160 * states.
161 */
162unsigned long long xen_sched_clock(void)
163{
164 struct vcpu_runstate_info state;
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165 cycle_t now;
166 u64 ret;
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167 s64 offset;
168
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169 /*
170 * Ideally sched_clock should be called on a per-cpu basis
171 * anyway, so preempt should already be disabled, but that's
172 * not current practice at the moment.
173 */
174 preempt_disable();
175
176 now = xen_clocksource_read();
177
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178 get_runstate_snapshot(&state);
179
180 WARN_ON(state.state != RUNSTATE_running);
181
182 offset = now - state.state_entry_time;
183 if (offset < 0)
184 offset = 0;
185
f120f13e 186 ret = state.time[RUNSTATE_blocked] +
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187 state.time[RUNSTATE_running] +
188 offset;
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189
190 preempt_enable();
191
192 return ret;
ab550288 193}
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194
195
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196/* Get the TSC speed from Xen */
197unsigned long xen_tsc_khz(void)
15c84731 198{
3807f345 199 struct pvclock_vcpu_time_info *info =
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200 &HYPERVISOR_shared_info->vcpu_info[0].time;
201
3807f345 202 return pvclock_tsc_khz(info);
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203}
204
ee7686bc 205cycle_t xen_clocksource_read(void)
15c84731 206{
1c7b67f7 207 struct pvclock_vcpu_time_info *src;
15c84731 208 cycle_t ret;
15c84731 209
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210 src = &get_cpu_var(xen_vcpu)->time;
211 ret = pvclock_clocksource_read(src);
212 put_cpu_var(xen_vcpu);
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213 return ret;
214}
215
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216static cycle_t xen_clocksource_get_cycles(struct clocksource *cs)
217{
218 return xen_clocksource_read();
219}
220
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221static void xen_read_wallclock(struct timespec *ts)
222{
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223 struct shared_info *s = HYPERVISOR_shared_info;
224 struct pvclock_wall_clock *wall_clock = &(s->wc);
225 struct pvclock_vcpu_time_info *vcpu_time;
15c84731 226
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227 vcpu_time = &get_cpu_var(xen_vcpu)->time;
228 pvclock_read_wallclock(wall_clock, vcpu_time, ts);
229 put_cpu_var(xen_vcpu);
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230}
231
232unsigned long xen_get_wallclock(void)
233{
234 struct timespec ts;
235
236 xen_read_wallclock(&ts);
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237 return ts.tv_sec;
238}
239
240int xen_set_wallclock(unsigned long now)
241{
242 /* do nothing for domU */
243 return -1;
244}
245
246static struct clocksource xen_clocksource __read_mostly = {
247 .name = "xen",
248 .rating = 400,
8e19608e 249 .read = xen_clocksource_get_cycles,
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250 .mask = ~0,
251 .mult = 1<<XEN_SHIFT, /* time directly in nanoseconds */
252 .shift = XEN_SHIFT,
253 .flags = CLOCK_SOURCE_IS_CONTINUOUS,
254};
255
256/*
257 Xen clockevent implementation
258
259 Xen has two clockevent implementations:
260
261 The old timer_op one works with all released versions of Xen prior
262 to version 3.0.4. This version of the hypervisor provides a
263 single-shot timer with nanosecond resolution. However, sharing the
264 same event channel is a 100Hz tick which is delivered while the
265 vcpu is running. We don't care about or use this tick, but it will
266 cause the core time code to think the timer fired too soon, and
267 will end up resetting it each time. It could be filtered, but
268 doing so has complications when the ktime clocksource is not yet
269 the xen clocksource (ie, at boot time).
270
271 The new vcpu_op-based timer interface allows the tick timer period
272 to be changed or turned off. The tick timer is not useful as a
273 periodic timer because events are only delivered to running vcpus.
274 The one-shot timer can report when a timeout is in the past, so
275 set_next_event is capable of returning -ETIME when appropriate.
276 This interface is used when available.
277*/
278
279
280/*
281 Get a hypervisor absolute time. In theory we could maintain an
282 offset between the kernel's time and the hypervisor's time, and
283 apply that to a kernel's absolute timeout. Unfortunately the
284 hypervisor and kernel times can drift even if the kernel is using
285 the Xen clocksource, because ntp can warp the kernel's clocksource.
286*/
287static s64 get_abs_timeout(unsigned long delta)
288{
289 return xen_clocksource_read() + delta;
290}
291
292static void xen_timerop_set_mode(enum clock_event_mode mode,
293 struct clock_event_device *evt)
294{
295 switch (mode) {
296 case CLOCK_EVT_MODE_PERIODIC:
297 /* unsupported */
298 WARN_ON(1);
299 break;
300
301 case CLOCK_EVT_MODE_ONESHOT:
18de5bc4 302 case CLOCK_EVT_MODE_RESUME:
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303 break;
304
305 case CLOCK_EVT_MODE_UNUSED:
306 case CLOCK_EVT_MODE_SHUTDOWN:
307 HYPERVISOR_set_timer_op(0); /* cancel timeout */
308 break;
309 }
310}
311
312static int xen_timerop_set_next_event(unsigned long delta,
313 struct clock_event_device *evt)
314{
315 WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT);
316
317 if (HYPERVISOR_set_timer_op(get_abs_timeout(delta)) < 0)
318 BUG();
319
320 /* We may have missed the deadline, but there's no real way of
321 knowing for sure. If the event was in the past, then we'll
322 get an immediate interrupt. */
323
324 return 0;
325}
326
327static const struct clock_event_device xen_timerop_clockevent = {
328 .name = "xen",
329 .features = CLOCK_EVT_FEAT_ONESHOT,
330
331 .max_delta_ns = 0xffffffff,
332 .min_delta_ns = TIMER_SLOP,
333
334 .mult = 1,
335 .shift = 0,
336 .rating = 500,
337
338 .set_mode = xen_timerop_set_mode,
339 .set_next_event = xen_timerop_set_next_event,
340};
341
342
343
344static void xen_vcpuop_set_mode(enum clock_event_mode mode,
345 struct clock_event_device *evt)
346{
347 int cpu = smp_processor_id();
348
349 switch (mode) {
350 case CLOCK_EVT_MODE_PERIODIC:
351 WARN_ON(1); /* unsupported */
352 break;
353
354 case CLOCK_EVT_MODE_ONESHOT:
355 if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL))
356 BUG();
357 break;
358
359 case CLOCK_EVT_MODE_UNUSED:
360 case CLOCK_EVT_MODE_SHUTDOWN:
361 if (HYPERVISOR_vcpu_op(VCPUOP_stop_singleshot_timer, cpu, NULL) ||
362 HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL))
363 BUG();
364 break;
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TG
365 case CLOCK_EVT_MODE_RESUME:
366 break;
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367 }
368}
369
370static int xen_vcpuop_set_next_event(unsigned long delta,
371 struct clock_event_device *evt)
372{
373 int cpu = smp_processor_id();
374 struct vcpu_set_singleshot_timer single;
375 int ret;
376
377 WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT);
378
379 single.timeout_abs_ns = get_abs_timeout(delta);
380 single.flags = VCPU_SSHOTTMR_future;
381
382 ret = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, cpu, &single);
383
384 BUG_ON(ret != 0 && ret != -ETIME);
385
386 return ret;
387}
388
389static const struct clock_event_device xen_vcpuop_clockevent = {
390 .name = "xen",
391 .features = CLOCK_EVT_FEAT_ONESHOT,
392
393 .max_delta_ns = 0xffffffff,
394 .min_delta_ns = TIMER_SLOP,
395
396 .mult = 1,
397 .shift = 0,
398 .rating = 500,
399
400 .set_mode = xen_vcpuop_set_mode,
401 .set_next_event = xen_vcpuop_set_next_event,
402};
403
404static const struct clock_event_device *xen_clockevent =
405 &xen_timerop_clockevent;
406static DEFINE_PER_CPU(struct clock_event_device, xen_clock_events);
407
408static irqreturn_t xen_timer_interrupt(int irq, void *dev_id)
409{
410 struct clock_event_device *evt = &__get_cpu_var(xen_clock_events);
411 irqreturn_t ret;
412
413 ret = IRQ_NONE;
414 if (evt->event_handler) {
415 evt->event_handler(evt);
416 ret = IRQ_HANDLED;
417 }
418
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419 do_stolen_accounting();
420
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421 return ret;
422}
423
f87e4cac 424void xen_setup_timer(int cpu)
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425{
426 const char *name;
427 struct clock_event_device *evt;
428 int irq;
429
430 printk(KERN_INFO "installing Xen timer for CPU %d\n", cpu);
431
432 name = kasprintf(GFP_KERNEL, "timer%d", cpu);
433 if (!name)
434 name = "<timer kasprintf failed>";
435
436 irq = bind_virq_to_irqhandler(VIRQ_TIMER, cpu, xen_timer_interrupt,
437 IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
438 name, NULL);
439
f87e4cac 440 evt = &per_cpu(xen_clock_events, cpu);
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441 memcpy(evt, xen_clockevent, sizeof(*evt));
442
320ab2b0 443 evt->cpumask = cpumask_of(cpu);
15c84731 444 evt->irq = irq;
15c84731 445
f91a8b44 446 setup_runstate_info(cpu);
f87e4cac
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447}
448
d68d82af
AN
449void xen_teardown_timer(int cpu)
450{
451 struct clock_event_device *evt;
452 BUG_ON(cpu == 0);
453 evt = &per_cpu(xen_clock_events, cpu);
454 unbind_from_irqhandler(evt->irq, NULL);
455}
456
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457void xen_setup_cpu_clockevents(void)
458{
459 BUG_ON(preemptible());
f91a8b44 460
f87e4cac 461 clockevents_register_device(&__get_cpu_var(xen_clock_events));
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462}
463
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464void xen_timer_resume(void)
465{
466 int cpu;
467
468 if (xen_clockevent != &xen_vcpuop_clockevent)
469 return;
470
471 for_each_online_cpu(cpu) {
472 if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL))
473 BUG();
474 }
475}
476
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477__init void xen_time_init(void)
478{
479 int cpu = smp_processor_id();
480
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481 clocksource_register(&xen_clocksource);
482
483 if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) {
f91a8b44 484 /* Successfully turned off 100Hz tick, so we have the
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485 vcpuop-based timer interface */
486 printk(KERN_DEBUG "Xen: using vcpuop timer interface\n");
487 xen_clockevent = &xen_vcpuop_clockevent;
488 }
489
490 /* Set initial system time with full resolution */
491 xen_read_wallclock(&xtime);
492 set_normalized_timespec(&wall_to_monotonic,
493 -xtime.tv_sec, -xtime.tv_nsec);
494
404ee5b1 495 setup_force_cpu_cap(X86_FEATURE_TSC);
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496
497 xen_setup_timer(cpu);
f87e4cac 498 xen_setup_cpu_clockevents();
15c84731 499}