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 <clocksource/hyperv_timer.h>
 22#include <asm/hyperv-tlfs.h>
 23#include <asm/mshyperv.h>
 24
 25static struct clock_event_device __percpu *hv_clock_event;
 26static u64 hv_sched_clock_offset __ro_after_init;
 27
 28/*
 29 * If false, we're using the old mechanism for stimer0 interrupts
 30 * where it sends a VMbus message when it expires. The old
 31 * mechanism is used when running on older versions of Hyper-V
 32 * that don't support Direct Mode. While Hyper-V provides
 33 * four stimer's per CPU, Linux uses only stimer0.
 34 *
 35 * Because Direct Mode does not require processing a VMbus
 36 * message, stimer interrupts can be enabled earlier in the
 37 * process of booting a CPU, and consistent with when timer
 38 * interrupts are enabled for other clocksource drivers.
 39 * However, for legacy versions of Hyper-V when Direct Mode
 40 * is not enabled, setting up stimer interrupts must be
 41 * delayed until VMbus is initialized and can process the
 42 * interrupt message.
 43 */
 44static bool direct_mode_enabled;
 45
 46static int stimer0_irq;
 47static int stimer0_vector;
 48static int stimer0_message_sint;
 49
 50/*
 51 * ISR for when stimer0 is operating in Direct Mode.  Direct Mode
 52 * does not use VMbus or any VMbus messages, so process here and not
 53 * in the VMbus driver code.
 54 */
 55void hv_stimer0_isr(void)
 56{
 57	struct clock_event_device *ce;
 58
 59	ce = this_cpu_ptr(hv_clock_event);
 60	ce->event_handler(ce);
 61}
 62EXPORT_SYMBOL_GPL(hv_stimer0_isr);
 63
 64static int hv_ce_set_next_event(unsigned long delta,
 65				struct clock_event_device *evt)
 66{
 67	u64 current_tick;
 68
 69	current_tick = hv_read_reference_counter();
 70	current_tick += delta;
 71	hv_init_timer(0, current_tick);
 72	return 0;
 73}
 74
 75static int hv_ce_shutdown(struct clock_event_device *evt)
 76{
 77	hv_init_timer(0, 0);
 78	hv_init_timer_config(0, 0);
 79	if (direct_mode_enabled)
 80		hv_disable_stimer0_percpu_irq(stimer0_irq);
 81
 82	return 0;
 83}
 84
 85static int hv_ce_set_oneshot(struct clock_event_device *evt)
 86{
 87	union hv_stimer_config timer_cfg;
 88
 89	timer_cfg.as_uint64 = 0;
 90	timer_cfg.enable = 1;
 91	timer_cfg.auto_enable = 1;
 92	if (direct_mode_enabled) {
 93		/*
 94		 * When it expires, the timer will directly interrupt
 95		 * on the specified hardware vector/IRQ.
 96		 */
 97		timer_cfg.direct_mode = 1;
 98		timer_cfg.apic_vector = stimer0_vector;
 99		hv_enable_stimer0_percpu_irq(stimer0_irq);
100	} else {
101		/*
102		 * When it expires, the timer will generate a VMbus message,
103		 * to be handled by the normal VMbus interrupt handler.
104		 */
105		timer_cfg.direct_mode = 0;
106		timer_cfg.sintx = stimer0_message_sint;
107	}
108	hv_init_timer_config(0, timer_cfg.as_uint64);
109	return 0;
110}
111
112/*
113 * hv_stimer_init - Per-cpu initialization of the clockevent
114 */
115static int hv_stimer_init(unsigned int cpu)
116{
117	struct clock_event_device *ce;
118
119	if (!hv_clock_event)
120		return 0;
121
122	ce = per_cpu_ptr(hv_clock_event, cpu);
123	ce->name = "Hyper-V clockevent";
124	ce->features = CLOCK_EVT_FEAT_ONESHOT;
125	ce->cpumask = cpumask_of(cpu);
126	ce->rating = 1000;
127	ce->set_state_shutdown = hv_ce_shutdown;
128	ce->set_state_oneshot = hv_ce_set_oneshot;
129	ce->set_next_event = hv_ce_set_next_event;
130
131	clockevents_config_and_register(ce,
132					HV_CLOCK_HZ,
133					HV_MIN_DELTA_TICKS,
134					HV_MAX_MAX_DELTA_TICKS);
135	return 0;
136}
137
138/*
139 * hv_stimer_cleanup - Per-cpu cleanup of the clockevent
140 */
141int hv_stimer_cleanup(unsigned int cpu)
142{
143	struct clock_event_device *ce;
144
145	if (!hv_clock_event)
146		return 0;
147
148	/*
149	 * In the legacy case where Direct Mode is not enabled
150	 * (which can only be on x86/64), stimer cleanup happens
151	 * relatively early in the CPU offlining process. We
152	 * must unbind the stimer-based clockevent device so
153	 * that the LAPIC timer can take over until clockevents
154	 * are no longer needed in the offlining process. Note
155	 * that clockevents_unbind_device() eventually calls
156	 * hv_ce_shutdown().
157	 *
158	 * The unbind should not be done when Direct Mode is
159	 * enabled because we may be on an architecture where
160	 * there are no other clockevent devices to fallback to.
161	 */
162	ce = per_cpu_ptr(hv_clock_event, cpu);
163	if (direct_mode_enabled)
164		hv_ce_shutdown(ce);
165	else
166		clockevents_unbind_device(ce, cpu);
167
168	return 0;
169}
170EXPORT_SYMBOL_GPL(hv_stimer_cleanup);
171
172/* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
173int hv_stimer_alloc(void)
174{
175	int ret = 0;
176
177	/*
178	 * Synthetic timers are always available except on old versions of
179	 * Hyper-V on x86.  In that case, return as error as Linux will use a
180	 * clockevent based on emulated LAPIC timer hardware.
181	 */
182	if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
183		return -EINVAL;
184
185	hv_clock_event = alloc_percpu(struct clock_event_device);
186	if (!hv_clock_event)
187		return -ENOMEM;
188
189	direct_mode_enabled = ms_hyperv.misc_features &
190			HV_STIMER_DIRECT_MODE_AVAILABLE;
191	if (direct_mode_enabled) {
192		ret = hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
193				hv_stimer0_isr);
194		if (ret)
195			goto free_percpu;
196
197		/*
198		 * Since we are in Direct Mode, stimer initialization
199		 * can be done now with a CPUHP value in the same range
200		 * as other clockevent devices.
201		 */
202		ret = cpuhp_setup_state(CPUHP_AP_HYPERV_TIMER_STARTING,
203				"clockevents/hyperv/stimer:starting",
204				hv_stimer_init, hv_stimer_cleanup);
205		if (ret < 0)
206			goto free_stimer0_irq;
207	}
208	return ret;
209
210free_stimer0_irq:
211	hv_remove_stimer0_irq(stimer0_irq);
212	stimer0_irq = 0;
213free_percpu:
214	free_percpu(hv_clock_event);
215	hv_clock_event = NULL;
216	return ret;
217}
218EXPORT_SYMBOL_GPL(hv_stimer_alloc);
219
220/*
221 * hv_stimer_legacy_init -- Called from the VMbus driver to handle
222 * the case when Direct Mode is not enabled, and the stimer
223 * must be initialized late in the CPU onlining process.
224 *
225 */
226void hv_stimer_legacy_init(unsigned int cpu, int sint)
227{
228	if (direct_mode_enabled)
229		return;
230
231	/*
232	 * This function gets called by each vCPU, so setting the
233	 * global stimer_message_sint value each time is conceptually
234	 * not ideal, but the value passed in is always the same and
235	 * it avoids introducing yet another interface into this
236	 * clocksource driver just to set the sint in the legacy case.
237	 */
238	stimer0_message_sint = sint;
239	(void)hv_stimer_init(cpu);
240}
241EXPORT_SYMBOL_GPL(hv_stimer_legacy_init);
242
243/*
244 * hv_stimer_legacy_cleanup -- Called from the VMbus driver to
245 * handle the case when Direct Mode is not enabled, and the
246 * stimer must be cleaned up early in the CPU offlining
247 * process.
248 */
249void hv_stimer_legacy_cleanup(unsigned int cpu)
250{
251	if (direct_mode_enabled)
252		return;
253	(void)hv_stimer_cleanup(cpu);
254}
255EXPORT_SYMBOL_GPL(hv_stimer_legacy_cleanup);
256
257
258/* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
259void hv_stimer_free(void)
260{
261	if (!hv_clock_event)
262		return;
263
264	if (direct_mode_enabled) {
265		cpuhp_remove_state(CPUHP_AP_HYPERV_TIMER_STARTING);
266		hv_remove_stimer0_irq(stimer0_irq);
267		stimer0_irq = 0;
268	}
269	free_percpu(hv_clock_event);
270	hv_clock_event = NULL;
271}
272EXPORT_SYMBOL_GPL(hv_stimer_free);
273
274/*
275 * Do a global cleanup of clockevents for the cases of kexec and
276 * vmbus exit
277 */
278void hv_stimer_global_cleanup(void)
279{
280	int	cpu;
281
282	/*
283	 * hv_stime_legacy_cleanup() will stop the stimer if Direct
284	 * Mode is not enabled, and fallback to the LAPIC timer.
285	 */
286	for_each_present_cpu(cpu) {
287		hv_stimer_legacy_cleanup(cpu);
288	}
289
290	/*
291	 * If Direct Mode is enabled, the cpuhp teardown callback
292	 * (hv_stimer_cleanup) will be run on all CPUs to stop the
293	 * stimers.
294	 */
295	hv_stimer_free();
296}
297EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
298
299/*
300 * Code and definitions for the Hyper-V clocksources.  Two
301 * clocksources are defined: one that reads the Hyper-V defined MSR, and
302 * the other that uses the TSC reference page feature as defined in the
303 * TLFS.  The MSR version is for compatibility with old versions of
304 * Hyper-V and 32-bit x86.  The TSC reference page version is preferred.
305 *
306 * The Hyper-V clocksource ratings of 250 are chosen to be below the
307 * TSC clocksource rating of 300.  In configurations where Hyper-V offers
308 * an InvariantTSC, the TSC is not marked "unstable", so the TSC clocksource
309 * is available and preferred.  With the higher rating, it will be the
310 * default.  On older hardware and Hyper-V versions, the TSC is marked
311 * "unstable", so no TSC clocksource is created and the selected Hyper-V
312 * clocksource will be the default.
313 */
314
315u64 (*hv_read_reference_counter)(void);
316EXPORT_SYMBOL_GPL(hv_read_reference_counter);
317
318static union {
319	struct ms_hyperv_tsc_page page;
320	u8 reserved[PAGE_SIZE];
321} tsc_pg __aligned(PAGE_SIZE);
322
323struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
324{
325	return &tsc_pg.page;
326}
327EXPORT_SYMBOL_GPL(hv_get_tsc_page);
328
329static u64 notrace read_hv_clock_tsc(void)
330{
331	u64 current_tick = hv_read_tsc_page(hv_get_tsc_page());
332
333	if (current_tick == U64_MAX)
334		hv_get_time_ref_count(current_tick);
335
336	return current_tick;
337}
338
339static u64 notrace read_hv_clock_tsc_cs(struct clocksource *arg)
340{
341	return read_hv_clock_tsc();
342}
343
344static u64 read_hv_sched_clock_tsc(void)
345{
346	return (read_hv_clock_tsc() - hv_sched_clock_offset) *
347		(NSEC_PER_SEC / HV_CLOCK_HZ);
348}
349
350static void suspend_hv_clock_tsc(struct clocksource *arg)
351{
352	u64 tsc_msr;
353
354	/* Disable the TSC page */
355	hv_get_reference_tsc(tsc_msr);
356	tsc_msr &= ~BIT_ULL(0);
357	hv_set_reference_tsc(tsc_msr);
358}
359
360
361static void resume_hv_clock_tsc(struct clocksource *arg)
362{
363	phys_addr_t phys_addr = virt_to_phys(&tsc_pg);
364	u64 tsc_msr;
365
366	/* Re-enable the TSC page */
367	hv_get_reference_tsc(tsc_msr);
368	tsc_msr &= GENMASK_ULL(11, 0);
369	tsc_msr |= BIT_ULL(0) | (u64)phys_addr;
370	hv_set_reference_tsc(tsc_msr);
371}
372
373static int hv_cs_enable(struct clocksource *cs)
374{
375	hv_enable_vdso_clocksource();
376	return 0;
377}
378
379static struct clocksource hyperv_cs_tsc = {
380	.name	= "hyperv_clocksource_tsc_page",
381	.rating	= 250,
382	.read	= read_hv_clock_tsc_cs,
383	.mask	= CLOCKSOURCE_MASK(64),
384	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
385	.suspend= suspend_hv_clock_tsc,
386	.resume	= resume_hv_clock_tsc,
387	.enable = hv_cs_enable,
388};
389
390static u64 notrace read_hv_clock_msr(void)
391{
392	u64 current_tick;
393	/*
394	 * Read the partition counter to get the current tick count. This count
395	 * is set to 0 when the partition is created and is incremented in
396	 * 100 nanosecond units.
397	 */
398	hv_get_time_ref_count(current_tick);
399	return current_tick;
400}
401
402static u64 notrace read_hv_clock_msr_cs(struct clocksource *arg)
403{
404	return read_hv_clock_msr();
405}
406
407static u64 read_hv_sched_clock_msr(void)
408{
409	return (read_hv_clock_msr() - hv_sched_clock_offset) *
410		(NSEC_PER_SEC / HV_CLOCK_HZ);
411}
412
413static struct clocksource hyperv_cs_msr = {
414	.name	= "hyperv_clocksource_msr",
415	.rating	= 250,
416	.read	= read_hv_clock_msr_cs,
417	.mask	= CLOCKSOURCE_MASK(64),
418	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
419};
420
421static bool __init hv_init_tsc_clocksource(void)
422{
423	u64		tsc_msr;
424	phys_addr_t	phys_addr;
425
426	if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
427		return false;
428
429	hv_read_reference_counter = read_hv_clock_tsc;
430	phys_addr = virt_to_phys(hv_get_tsc_page());
431
432	/*
433	 * The Hyper-V TLFS specifies to preserve the value of reserved
434	 * bits in registers. So read the existing value, preserve the
435	 * low order 12 bits, and add in the guest physical address
436	 * (which already has at least the low 12 bits set to zero since
437	 * it is page aligned). Also set the "enable" bit, which is bit 0.
438	 */
439	hv_get_reference_tsc(tsc_msr);
440	tsc_msr &= GENMASK_ULL(11, 0);
441	tsc_msr = tsc_msr | 0x1 | (u64)phys_addr;
442	hv_set_reference_tsc(tsc_msr);
443
444	hv_set_clocksource_vdso(hyperv_cs_tsc);
445	clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
446
447	hv_sched_clock_offset = hv_read_reference_counter();
448	hv_setup_sched_clock(read_hv_sched_clock_tsc);
449
450	return true;
451}
452
453void __init hv_init_clocksource(void)
454{
455	/*
456	 * Try to set up the TSC page clocksource. If it succeeds, we're
457	 * done. Otherwise, set up the MSR clocksoruce.  At least one of
458	 * these will always be available except on very old versions of
459	 * Hyper-V on x86.  In that case we won't have a Hyper-V
460	 * clocksource, but Linux will still run with a clocksource based
461	 * on the emulated PIT or LAPIC timer.
462	 */
463	if (hv_init_tsc_clocksource())
464		return;
465
466	if (!(ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE))
467		return;
468
469	hv_read_reference_counter = read_hv_clock_msr;
470	clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
471
472	hv_sched_clock_offset = hv_read_reference_counter();
473	hv_setup_sched_clock(read_hv_sched_clock_msr);
474}
475EXPORT_SYMBOL_GPL(hv_init_clocksource);