1 | // SPDX-License-Identifier: GPL-2.0 |
2 | |
3 | /* |
4 | * Clocksource driver for the synthetic counter and timers |
5 | * provided by the Hyper-V hypervisor to guest VMs, as described |
6 | * in the Hyper-V Top Level Functional Spec (TLFS). This driver |
7 | * is instruction set architecture independent. |
8 | * |
9 | * Copyright (C) 2019, Microsoft, Inc. |
10 | * |
11 | * Author: Michael Kelley <mikelley@microsoft.com> |
12 | */ |
13 | |
14 | #include <linux/percpu.h> |
15 | #include <linux/cpumask.h> |
16 | #include <linux/clockchips.h> |
17 | #include <linux/clocksource.h> |
18 | #include <linux/sched_clock.h> |
19 | #include <linux/mm.h> |
20 | #include <linux/cpuhotplug.h> |
21 | #include <linux/interrupt.h> |
22 | #include <linux/irq.h> |
23 | #include <linux/acpi.h> |
24 | #include <linux/hyperv.h> |
25 | #include <clocksource/hyperv_timer.h> |
26 | #include <asm/hyperv-tlfs.h> |
27 | #include <asm/mshyperv.h> |
28 | |
29 | static struct clock_event_device __percpu *hv_clock_event; |
30 | static u64 hv_sched_clock_offset __ro_after_init; |
31 | |
32 | /* |
33 | * If false, we're using the old mechanism for stimer0 interrupts |
34 | * where it sends a VMbus message when it expires. The old |
35 | * mechanism is used when running on older versions of Hyper-V |
36 | * that don't support Direct Mode. While Hyper-V provides |
37 | * four stimer's per CPU, Linux uses only stimer0. |
38 | * |
39 | * Because Direct Mode does not require processing a VMbus |
40 | * message, stimer interrupts can be enabled earlier in the |
41 | * process of booting a CPU, and consistent with when timer |
42 | * interrupts are enabled for other clocksource drivers. |
43 | * However, for legacy versions of Hyper-V when Direct Mode |
44 | * is not enabled, setting up stimer interrupts must be |
45 | * delayed until VMbus is initialized and can process the |
46 | * interrupt message. |
47 | */ |
48 | static bool direct_mode_enabled; |
49 | |
50 | static int stimer0_irq = -1; |
51 | static int stimer0_message_sint; |
52 | static __maybe_unused DEFINE_PER_CPU(long, stimer0_evt); |
53 | |
54 | /* |
55 | * Common code for stimer0 interrupts coming via Direct Mode or |
56 | * as a VMbus message. |
57 | */ |
58 | void hv_stimer0_isr(void) |
59 | { |
60 | struct clock_event_device *ce; |
61 | |
62 | ce = this_cpu_ptr(hv_clock_event); |
63 | ce->event_handler(ce); |
64 | } |
65 | EXPORT_SYMBOL_GPL(hv_stimer0_isr); |
66 | |
67 | /* |
68 | * stimer0 interrupt handler for architectures that support |
69 | * per-cpu interrupts, which also implies Direct Mode. |
70 | */ |
71 | static irqreturn_t __maybe_unused hv_stimer0_percpu_isr(int irq, void *dev_id) |
72 | { |
73 | hv_stimer0_isr(); |
74 | return IRQ_HANDLED; |
75 | } |
76 | |
77 | static int hv_ce_set_next_event(unsigned long delta, |
78 | struct clock_event_device *evt) |
79 | { |
80 | u64 current_tick; |
81 | |
82 | current_tick = hv_read_reference_counter(); |
83 | current_tick += delta; |
84 | hv_set_msr(HV_MSR_STIMER0_COUNT, value: current_tick); |
85 | return 0; |
86 | } |
87 | |
88 | static int hv_ce_shutdown(struct clock_event_device *evt) |
89 | { |
90 | hv_set_msr(HV_MSR_STIMER0_COUNT, value: 0); |
91 | hv_set_msr(HV_MSR_STIMER0_CONFIG, value: 0); |
92 | if (direct_mode_enabled && stimer0_irq >= 0) |
93 | disable_percpu_irq(irq: stimer0_irq); |
94 | |
95 | return 0; |
96 | } |
97 | |
98 | static int hv_ce_set_oneshot(struct clock_event_device *evt) |
99 | { |
100 | union hv_stimer_config timer_cfg; |
101 | |
102 | timer_cfg.as_uint64 = 0; |
103 | timer_cfg.enable = 1; |
104 | timer_cfg.auto_enable = 1; |
105 | if (direct_mode_enabled) { |
106 | /* |
107 | * When it expires, the timer will directly interrupt |
108 | * on the specified hardware vector/IRQ. |
109 | */ |
110 | timer_cfg.direct_mode = 1; |
111 | timer_cfg.apic_vector = HYPERV_STIMER0_VECTOR; |
112 | if (stimer0_irq >= 0) |
113 | enable_percpu_irq(irq: stimer0_irq, type: IRQ_TYPE_NONE); |
114 | } else { |
115 | /* |
116 | * When it expires, the timer will generate a VMbus message, |
117 | * to be handled by the normal VMbus interrupt handler. |
118 | */ |
119 | timer_cfg.direct_mode = 0; |
120 | timer_cfg.sintx = stimer0_message_sint; |
121 | } |
122 | hv_set_msr(HV_MSR_STIMER0_CONFIG, value: timer_cfg.as_uint64); |
123 | return 0; |
124 | } |
125 | |
126 | /* |
127 | * hv_stimer_init - Per-cpu initialization of the clockevent |
128 | */ |
129 | static int hv_stimer_init(unsigned int cpu) |
130 | { |
131 | struct clock_event_device *ce; |
132 | |
133 | if (!hv_clock_event) |
134 | return 0; |
135 | |
136 | ce = per_cpu_ptr(hv_clock_event, cpu); |
137 | ce->name = "Hyper-V clockevent" ; |
138 | ce->features = CLOCK_EVT_FEAT_ONESHOT; |
139 | ce->cpumask = cpumask_of(cpu); |
140 | ce->rating = 1000; |
141 | ce->set_state_shutdown = hv_ce_shutdown; |
142 | ce->set_state_oneshot = hv_ce_set_oneshot; |
143 | ce->set_next_event = hv_ce_set_next_event; |
144 | |
145 | clockevents_config_and_register(dev: ce, |
146 | HV_CLOCK_HZ, |
147 | HV_MIN_DELTA_TICKS, |
148 | HV_MAX_MAX_DELTA_TICKS); |
149 | return 0; |
150 | } |
151 | |
152 | /* |
153 | * hv_stimer_cleanup - Per-cpu cleanup of the clockevent |
154 | */ |
155 | int hv_stimer_cleanup(unsigned int cpu) |
156 | { |
157 | struct clock_event_device *ce; |
158 | |
159 | if (!hv_clock_event) |
160 | return 0; |
161 | |
162 | /* |
163 | * In the legacy case where Direct Mode is not enabled |
164 | * (which can only be on x86/64), stimer cleanup happens |
165 | * relatively early in the CPU offlining process. We |
166 | * must unbind the stimer-based clockevent device so |
167 | * that the LAPIC timer can take over until clockevents |
168 | * are no longer needed in the offlining process. Note |
169 | * that clockevents_unbind_device() eventually calls |
170 | * hv_ce_shutdown(). |
171 | * |
172 | * The unbind should not be done when Direct Mode is |
173 | * enabled because we may be on an architecture where |
174 | * there are no other clockevent devices to fallback to. |
175 | */ |
176 | ce = per_cpu_ptr(hv_clock_event, cpu); |
177 | if (direct_mode_enabled) |
178 | hv_ce_shutdown(evt: ce); |
179 | else |
180 | clockevents_unbind_device(ced: ce, cpu); |
181 | |
182 | return 0; |
183 | } |
184 | EXPORT_SYMBOL_GPL(hv_stimer_cleanup); |
185 | |
186 | /* |
187 | * These placeholders are overridden by arch specific code on |
188 | * architectures that need special setup of the stimer0 IRQ because |
189 | * they don't support per-cpu IRQs (such as x86/x64). |
190 | */ |
191 | void __weak hv_setup_stimer0_handler(void (*handler)(void)) |
192 | { |
193 | }; |
194 | |
195 | void __weak hv_remove_stimer0_handler(void) |
196 | { |
197 | }; |
198 | |
199 | #ifdef CONFIG_ACPI |
200 | /* Called only on architectures with per-cpu IRQs (i.e., not x86/x64) */ |
201 | static int hv_setup_stimer0_irq(void) |
202 | { |
203 | int ret; |
204 | |
205 | ret = acpi_register_gsi(NULL, HYPERV_STIMER0_VECTOR, |
206 | ACPI_EDGE_SENSITIVE, ACPI_ACTIVE_HIGH); |
207 | if (ret < 0) { |
208 | pr_err("Can't register Hyper-V stimer0 GSI. Error %d" , ret); |
209 | return ret; |
210 | } |
211 | stimer0_irq = ret; |
212 | |
213 | ret = request_percpu_irq(irq: stimer0_irq, handler: hv_stimer0_percpu_isr, |
214 | devname: "Hyper-V stimer0" , percpu_dev_id: &stimer0_evt); |
215 | if (ret) { |
216 | pr_err("Can't request Hyper-V stimer0 IRQ %d. Error %d" , |
217 | stimer0_irq, ret); |
218 | acpi_unregister_gsi(gsi: stimer0_irq); |
219 | stimer0_irq = -1; |
220 | } |
221 | return ret; |
222 | } |
223 | |
224 | static void hv_remove_stimer0_irq(void) |
225 | { |
226 | if (stimer0_irq == -1) { |
227 | hv_remove_stimer0_handler(); |
228 | } else { |
229 | free_percpu_irq(stimer0_irq, &stimer0_evt); |
230 | acpi_unregister_gsi(gsi: stimer0_irq); |
231 | stimer0_irq = -1; |
232 | } |
233 | } |
234 | #else |
235 | static int hv_setup_stimer0_irq(void) |
236 | { |
237 | return 0; |
238 | } |
239 | |
240 | static void hv_remove_stimer0_irq(void) |
241 | { |
242 | } |
243 | #endif |
244 | |
245 | /* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */ |
246 | int hv_stimer_alloc(bool have_percpu_irqs) |
247 | { |
248 | int ret; |
249 | |
250 | /* |
251 | * Synthetic timers are always available except on old versions of |
252 | * Hyper-V on x86. In that case, return as error as Linux will use a |
253 | * clockevent based on emulated LAPIC timer hardware. |
254 | */ |
255 | if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE)) |
256 | return -EINVAL; |
257 | |
258 | hv_clock_event = alloc_percpu(struct clock_event_device); |
259 | if (!hv_clock_event) |
260 | return -ENOMEM; |
261 | |
262 | direct_mode_enabled = ms_hyperv.misc_features & |
263 | HV_STIMER_DIRECT_MODE_AVAILABLE; |
264 | |
265 | /* |
266 | * If Direct Mode isn't enabled, the remainder of the initialization |
267 | * is done later by hv_stimer_legacy_init() |
268 | */ |
269 | if (!direct_mode_enabled) |
270 | return 0; |
271 | |
272 | if (have_percpu_irqs) { |
273 | ret = hv_setup_stimer0_irq(); |
274 | if (ret) |
275 | goto free_clock_event; |
276 | } else { |
277 | hv_setup_stimer0_handler(handler: hv_stimer0_isr); |
278 | } |
279 | |
280 | /* |
281 | * Since we are in Direct Mode, stimer initialization |
282 | * can be done now with a CPUHP value in the same range |
283 | * as other clockevent devices. |
284 | */ |
285 | ret = cpuhp_setup_state(state: CPUHP_AP_HYPERV_TIMER_STARTING, |
286 | name: "clockevents/hyperv/stimer:starting" , |
287 | startup: hv_stimer_init, teardown: hv_stimer_cleanup); |
288 | if (ret < 0) { |
289 | hv_remove_stimer0_irq(); |
290 | goto free_clock_event; |
291 | } |
292 | return ret; |
293 | |
294 | free_clock_event: |
295 | free_percpu(pdata: hv_clock_event); |
296 | hv_clock_event = NULL; |
297 | return ret; |
298 | } |
299 | EXPORT_SYMBOL_GPL(hv_stimer_alloc); |
300 | |
301 | /* |
302 | * hv_stimer_legacy_init -- Called from the VMbus driver to handle |
303 | * the case when Direct Mode is not enabled, and the stimer |
304 | * must be initialized late in the CPU onlining process. |
305 | * |
306 | */ |
307 | void hv_stimer_legacy_init(unsigned int cpu, int sint) |
308 | { |
309 | if (direct_mode_enabled) |
310 | return; |
311 | |
312 | /* |
313 | * This function gets called by each vCPU, so setting the |
314 | * global stimer_message_sint value each time is conceptually |
315 | * not ideal, but the value passed in is always the same and |
316 | * it avoids introducing yet another interface into this |
317 | * clocksource driver just to set the sint in the legacy case. |
318 | */ |
319 | stimer0_message_sint = sint; |
320 | (void)hv_stimer_init(cpu); |
321 | } |
322 | EXPORT_SYMBOL_GPL(hv_stimer_legacy_init); |
323 | |
324 | /* |
325 | * hv_stimer_legacy_cleanup -- Called from the VMbus driver to |
326 | * handle the case when Direct Mode is not enabled, and the |
327 | * stimer must be cleaned up early in the CPU offlining |
328 | * process. |
329 | */ |
330 | void hv_stimer_legacy_cleanup(unsigned int cpu) |
331 | { |
332 | if (direct_mode_enabled) |
333 | return; |
334 | (void)hv_stimer_cleanup(cpu); |
335 | } |
336 | EXPORT_SYMBOL_GPL(hv_stimer_legacy_cleanup); |
337 | |
338 | /* |
339 | * Do a global cleanup of clockevents for the cases of kexec and |
340 | * vmbus exit |
341 | */ |
342 | void hv_stimer_global_cleanup(void) |
343 | { |
344 | int cpu; |
345 | |
346 | /* |
347 | * hv_stime_legacy_cleanup() will stop the stimer if Direct |
348 | * Mode is not enabled, and fallback to the LAPIC timer. |
349 | */ |
350 | for_each_present_cpu(cpu) { |
351 | hv_stimer_legacy_cleanup(cpu); |
352 | } |
353 | |
354 | if (!hv_clock_event) |
355 | return; |
356 | |
357 | if (direct_mode_enabled) { |
358 | cpuhp_remove_state(state: CPUHP_AP_HYPERV_TIMER_STARTING); |
359 | hv_remove_stimer0_irq(); |
360 | stimer0_irq = -1; |
361 | } |
362 | free_percpu(pdata: hv_clock_event); |
363 | hv_clock_event = NULL; |
364 | |
365 | } |
366 | EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup); |
367 | |
368 | static __always_inline u64 read_hv_clock_msr(void) |
369 | { |
370 | /* |
371 | * Read the partition counter to get the current tick count. This count |
372 | * is set to 0 when the partition is created and is incremented in 100 |
373 | * nanosecond units. |
374 | * |
375 | * Use hv_raw_get_msr() because this function is used from |
376 | * noinstr. Notable; while HV_MSR_TIME_REF_COUNT is a synthetic |
377 | * register it doesn't need the GHCB path. |
378 | */ |
379 | return hv_raw_get_msr(HV_MSR_TIME_REF_COUNT); |
380 | } |
381 | |
382 | /* |
383 | * Code and definitions for the Hyper-V clocksources. Two |
384 | * clocksources are defined: one that reads the Hyper-V defined MSR, and |
385 | * the other that uses the TSC reference page feature as defined in the |
386 | * TLFS. The MSR version is for compatibility with old versions of |
387 | * Hyper-V and 32-bit x86. The TSC reference page version is preferred. |
388 | */ |
389 | |
390 | static union { |
391 | struct ms_hyperv_tsc_page page; |
392 | u8 reserved[PAGE_SIZE]; |
393 | } tsc_pg __bss_decrypted __aligned(PAGE_SIZE); |
394 | |
395 | static struct ms_hyperv_tsc_page *tsc_page = &tsc_pg.page; |
396 | static unsigned long tsc_pfn; |
397 | |
398 | unsigned long hv_get_tsc_pfn(void) |
399 | { |
400 | return tsc_pfn; |
401 | } |
402 | EXPORT_SYMBOL_GPL(hv_get_tsc_pfn); |
403 | |
404 | struct ms_hyperv_tsc_page *hv_get_tsc_page(void) |
405 | { |
406 | return tsc_page; |
407 | } |
408 | EXPORT_SYMBOL_GPL(hv_get_tsc_page); |
409 | |
410 | static __always_inline u64 read_hv_clock_tsc(void) |
411 | { |
412 | u64 cur_tsc, time; |
413 | |
414 | /* |
415 | * The Hyper-V Top-Level Function Spec (TLFS), section Timers, |
416 | * subsection Refererence Counter, guarantees that the TSC and MSR |
417 | * times are in sync and monotonic. Therefore we can fall back |
418 | * to the MSR in case the TSC page indicates unavailability. |
419 | */ |
420 | if (!hv_read_tsc_page_tsc(tsc_pg: tsc_page, cur_tsc: &cur_tsc, time: &time)) |
421 | time = read_hv_clock_msr(); |
422 | |
423 | return time; |
424 | } |
425 | |
426 | static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg) |
427 | { |
428 | return read_hv_clock_tsc(); |
429 | } |
430 | |
431 | static u64 noinstr read_hv_sched_clock_tsc(void) |
432 | { |
433 | return (read_hv_clock_tsc() - hv_sched_clock_offset) * |
434 | (NSEC_PER_SEC / HV_CLOCK_HZ); |
435 | } |
436 | |
437 | static void suspend_hv_clock_tsc(struct clocksource *arg) |
438 | { |
439 | union hv_reference_tsc_msr tsc_msr; |
440 | |
441 | /* Disable the TSC page */ |
442 | tsc_msr.as_uint64 = hv_get_msr(HV_MSR_REFERENCE_TSC); |
443 | tsc_msr.enable = 0; |
444 | hv_set_msr(HV_MSR_REFERENCE_TSC, value: tsc_msr.as_uint64); |
445 | } |
446 | |
447 | |
448 | static void resume_hv_clock_tsc(struct clocksource *arg) |
449 | { |
450 | union hv_reference_tsc_msr tsc_msr; |
451 | |
452 | /* Re-enable the TSC page */ |
453 | tsc_msr.as_uint64 = hv_get_msr(HV_MSR_REFERENCE_TSC); |
454 | tsc_msr.enable = 1; |
455 | tsc_msr.pfn = tsc_pfn; |
456 | hv_set_msr(HV_MSR_REFERENCE_TSC, value: tsc_msr.as_uint64); |
457 | } |
458 | |
459 | #ifdef HAVE_VDSO_CLOCKMODE_HVCLOCK |
460 | static int hv_cs_enable(struct clocksource *cs) |
461 | { |
462 | vclocks_set_used(which: VDSO_CLOCKMODE_HVCLOCK); |
463 | return 0; |
464 | } |
465 | #endif |
466 | |
467 | static struct clocksource hyperv_cs_tsc = { |
468 | .name = "hyperv_clocksource_tsc_page" , |
469 | .rating = 500, |
470 | .read = read_hv_clock_tsc_cs, |
471 | .mask = CLOCKSOURCE_MASK(64), |
472 | .flags = CLOCK_SOURCE_IS_CONTINUOUS, |
473 | .suspend= suspend_hv_clock_tsc, |
474 | .resume = resume_hv_clock_tsc, |
475 | #ifdef HAVE_VDSO_CLOCKMODE_HVCLOCK |
476 | .enable = hv_cs_enable, |
477 | .vdso_clock_mode = VDSO_CLOCKMODE_HVCLOCK, |
478 | #else |
479 | .vdso_clock_mode = VDSO_CLOCKMODE_NONE, |
480 | #endif |
481 | }; |
482 | |
483 | static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg) |
484 | { |
485 | return read_hv_clock_msr(); |
486 | } |
487 | |
488 | static struct clocksource hyperv_cs_msr = { |
489 | .name = "hyperv_clocksource_msr" , |
490 | .rating = 495, |
491 | .read = read_hv_clock_msr_cs, |
492 | .mask = CLOCKSOURCE_MASK(64), |
493 | .flags = CLOCK_SOURCE_IS_CONTINUOUS, |
494 | }; |
495 | |
496 | /* |
497 | * Reference to pv_ops must be inline so objtool |
498 | * detection of noinstr violations can work correctly. |
499 | */ |
500 | #ifdef CONFIG_GENERIC_SCHED_CLOCK |
501 | static __always_inline void hv_setup_sched_clock(void *sched_clock) |
502 | { |
503 | /* |
504 | * We're on an architecture with generic sched clock (not x86/x64). |
505 | * The Hyper-V sched clock read function returns nanoseconds, not |
506 | * the normal 100ns units of the Hyper-V synthetic clock. |
507 | */ |
508 | sched_clock_register(sched_clock, 64, NSEC_PER_SEC); |
509 | } |
510 | #elif defined CONFIG_PARAVIRT |
511 | static __always_inline void hv_setup_sched_clock(void *sched_clock) |
512 | { |
513 | /* We're on x86/x64 *and* using PV ops */ |
514 | paravirt_set_sched_clock(func: sched_clock); |
515 | } |
516 | #else /* !CONFIG_GENERIC_SCHED_CLOCK && !CONFIG_PARAVIRT */ |
517 | static __always_inline void hv_setup_sched_clock(void *sched_clock) {} |
518 | #endif /* CONFIG_GENERIC_SCHED_CLOCK */ |
519 | |
520 | static void __init hv_init_tsc_clocksource(void) |
521 | { |
522 | union hv_reference_tsc_msr tsc_msr; |
523 | |
524 | /* |
525 | * If Hyper-V offers TSC_INVARIANT, then the virtualized TSC correctly |
526 | * handles frequency and offset changes due to live migration, |
527 | * pause/resume, and other VM management operations. So lower the |
528 | * Hyper-V Reference TSC rating, causing the generic TSC to be used. |
529 | * TSC_INVARIANT is not offered on ARM64, so the Hyper-V Reference |
530 | * TSC will be preferred over the virtualized ARM64 arch counter. |
531 | */ |
532 | if (ms_hyperv.features & HV_ACCESS_TSC_INVARIANT) { |
533 | hyperv_cs_tsc.rating = 250; |
534 | hyperv_cs_msr.rating = 245; |
535 | } |
536 | |
537 | if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE)) |
538 | return; |
539 | |
540 | hv_read_reference_counter = read_hv_clock_tsc; |
541 | |
542 | /* |
543 | * TSC page mapping works differently in root compared to guest. |
544 | * - In guest partition the guest PFN has to be passed to the |
545 | * hypervisor. |
546 | * - In root partition it's other way around: it has to map the PFN |
547 | * provided by the hypervisor. |
548 | * But it can't be mapped right here as it's too early and MMU isn't |
549 | * ready yet. So, we only set the enable bit here and will remap the |
550 | * page later in hv_remap_tsc_clocksource(). |
551 | * |
552 | * It worth mentioning, that TSC clocksource read function |
553 | * (read_hv_clock_tsc) has a MSR-based fallback mechanism, used when |
554 | * TSC page is zeroed (which is the case until the PFN is remapped) and |
555 | * thus TSC clocksource will work even without the real TSC page |
556 | * mapped. |
557 | */ |
558 | tsc_msr.as_uint64 = hv_get_msr(HV_MSR_REFERENCE_TSC); |
559 | if (hv_root_partition) |
560 | tsc_pfn = tsc_msr.pfn; |
561 | else |
562 | tsc_pfn = HVPFN_DOWN(virt_to_phys(tsc_page)); |
563 | tsc_msr.enable = 1; |
564 | tsc_msr.pfn = tsc_pfn; |
565 | hv_set_msr(HV_MSR_REFERENCE_TSC, value: tsc_msr.as_uint64); |
566 | |
567 | clocksource_register_hz(cs: &hyperv_cs_tsc, NSEC_PER_SEC/100); |
568 | |
569 | /* |
570 | * If TSC is invariant, then let it stay as the sched clock since it |
571 | * will be faster than reading the TSC page. But if not invariant, use |
572 | * the TSC page so that live migrations across hosts with different |
573 | * frequencies is handled correctly. |
574 | */ |
575 | if (!(ms_hyperv.features & HV_ACCESS_TSC_INVARIANT)) { |
576 | hv_sched_clock_offset = hv_read_reference_counter(); |
577 | hv_setup_sched_clock(sched_clock: read_hv_sched_clock_tsc); |
578 | } |
579 | } |
580 | |
581 | void __init hv_init_clocksource(void) |
582 | { |
583 | /* |
584 | * Try to set up the TSC page clocksource, then the MSR clocksource. |
585 | * At least one of these will always be available except on very old |
586 | * versions of Hyper-V on x86. In that case we won't have a Hyper-V |
587 | * clocksource, but Linux will still run with a clocksource based |
588 | * on the emulated PIT or LAPIC timer. |
589 | * |
590 | * Never use the MSR clocksource as sched clock. It's too slow. |
591 | * Better to use the native sched clock as the fallback. |
592 | */ |
593 | hv_init_tsc_clocksource(); |
594 | |
595 | if (ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE) |
596 | clocksource_register_hz(cs: &hyperv_cs_msr, NSEC_PER_SEC/100); |
597 | } |
598 | |
599 | void __init hv_remap_tsc_clocksource(void) |
600 | { |
601 | if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE)) |
602 | return; |
603 | |
604 | if (!hv_root_partition) { |
605 | WARN(1, "%s: attempt to remap TSC page in guest partition\n" , |
606 | __func__); |
607 | return; |
608 | } |
609 | |
610 | tsc_page = memremap(offset: tsc_pfn << HV_HYP_PAGE_SHIFT, size: sizeof(tsc_pg), |
611 | flags: MEMREMAP_WB); |
612 | if (!tsc_page) |
613 | pr_err("Failed to remap Hyper-V TSC page.\n" ); |
614 | } |
615 | |