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 <clocksource/hyperv_timer.h>
 21#include <asm/hyperv-tlfs.h>
 22#include <asm/mshyperv.h>
 23
 24static struct clock_event_device __percpu *hv_clock_event;
 25static u64 hv_sched_clock_offset __ro_after_init;
 26
 27/*
 28 * If false, we're using the old mechanism for stimer0 interrupts
 29 * where it sends a VMbus message when it expires. The old
 30 * mechanism is used when running on older versions of Hyper-V
 31 * that don't support Direct Mode. While Hyper-V provides
 32 * four stimer's per CPU, Linux uses only stimer0.
 33 */
 34static bool direct_mode_enabled;
 35
 36static int stimer0_irq;
 37static int stimer0_vector;
 38static int stimer0_message_sint;
 39
 40/*
 41 * ISR for when stimer0 is operating in Direct Mode.  Direct Mode
 42 * does not use VMbus or any VMbus messages, so process here and not
 43 * in the VMbus driver code.
 44 */
 45void hv_stimer0_isr(void)
 46{
 47	struct clock_event_device *ce;
 48
 49	ce = this_cpu_ptr(hv_clock_event);
 50	ce->event_handler(ce);
 51}
 52EXPORT_SYMBOL_GPL(hv_stimer0_isr);
 53
 54static int hv_ce_set_next_event(unsigned long delta,
 55				struct clock_event_device *evt)
 56{
 57	u64 current_tick;
 58
 59	current_tick = hyperv_cs->read(NULL);
 60	current_tick += delta;
 61	hv_init_timer(0, current_tick);
 62	return 0;
 63}
 64
 65static int hv_ce_shutdown(struct clock_event_device *evt)
 66{
 67	hv_init_timer(0, 0);
 68	hv_init_timer_config(0, 0);
 69	if (direct_mode_enabled)
 70		hv_disable_stimer0_percpu_irq(stimer0_irq);
 71
 72	return 0;
 73}
 74
 75static int hv_ce_set_oneshot(struct clock_event_device *evt)
 76{
 77	union hv_stimer_config timer_cfg;
 78
 79	timer_cfg.as_uint64 = 0;
 80	timer_cfg.enable = 1;
 81	timer_cfg.auto_enable = 1;
 82	if (direct_mode_enabled) {
 83		/*
 84		 * When it expires, the timer will directly interrupt
 85		 * on the specified hardware vector/IRQ.
 86		 */
 87		timer_cfg.direct_mode = 1;
 88		timer_cfg.apic_vector = stimer0_vector;
 89		hv_enable_stimer0_percpu_irq(stimer0_irq);
 90	} else {
 91		/*
 92		 * When it expires, the timer will generate a VMbus message,
 93		 * to be handled by the normal VMbus interrupt handler.
 94		 */
 95		timer_cfg.direct_mode = 0;
 96		timer_cfg.sintx = stimer0_message_sint;
 97	}
 98	hv_init_timer_config(0, timer_cfg.as_uint64);
 99	return 0;
100}
101
102/*
103 * hv_stimer_init - Per-cpu initialization of the clockevent
104 */
105void hv_stimer_init(unsigned int cpu)
106{
107	struct clock_event_device *ce;
108
109	/*
110	 * Synthetic timers are always available except on old versions of
111	 * Hyper-V on x86.  In that case, just return as Linux will use a
112	 * clocksource based on emulated PIT or LAPIC timer hardware.
113	 */
114	if (!(ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE))
115		return;
116
117	ce = per_cpu_ptr(hv_clock_event, cpu);
118	ce->name = "Hyper-V clockevent";
119	ce->features = CLOCK_EVT_FEAT_ONESHOT;
120	ce->cpumask = cpumask_of(cpu);
121	ce->rating = 1000;
122	ce->set_state_shutdown = hv_ce_shutdown;
123	ce->set_state_oneshot = hv_ce_set_oneshot;
124	ce->set_next_event = hv_ce_set_next_event;
125
126	clockevents_config_and_register(ce,
127					HV_CLOCK_HZ,
128					HV_MIN_DELTA_TICKS,
129					HV_MAX_MAX_DELTA_TICKS);
130}
131EXPORT_SYMBOL_GPL(hv_stimer_init);
132
133/*
134 * hv_stimer_cleanup - Per-cpu cleanup of the clockevent
135 */
136void hv_stimer_cleanup(unsigned int cpu)
137{
138	struct clock_event_device *ce;
139
140	/* Turn off clockevent device */
141	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
142		ce = per_cpu_ptr(hv_clock_event, cpu);
143		hv_ce_shutdown(ce);
144	}
145}
146EXPORT_SYMBOL_GPL(hv_stimer_cleanup);
147
148/* hv_stimer_alloc - Global initialization of the clockevent and stimer0 */
149int hv_stimer_alloc(int sint)
150{
151	int ret;
152
153	hv_clock_event = alloc_percpu(struct clock_event_device);
154	if (!hv_clock_event)
155		return -ENOMEM;
156
157	direct_mode_enabled = ms_hyperv.misc_features &
158			HV_STIMER_DIRECT_MODE_AVAILABLE;
159	if (direct_mode_enabled) {
160		ret = hv_setup_stimer0_irq(&stimer0_irq, &stimer0_vector,
161				hv_stimer0_isr);
162		if (ret) {
163			free_percpu(hv_clock_event);
164			hv_clock_event = NULL;
165			return ret;
166		}
167	}
168
169	stimer0_message_sint = sint;
170	return 0;
171}
172EXPORT_SYMBOL_GPL(hv_stimer_alloc);
173
174/* hv_stimer_free - Free global resources allocated by hv_stimer_alloc() */
175void hv_stimer_free(void)
176{
177	if (direct_mode_enabled && (stimer0_irq != 0)) {
178		hv_remove_stimer0_irq(stimer0_irq);
179		stimer0_irq = 0;
180	}
181	free_percpu(hv_clock_event);
182	hv_clock_event = NULL;
183}
184EXPORT_SYMBOL_GPL(hv_stimer_free);
185
186/*
187 * Do a global cleanup of clockevents for the cases of kexec and
188 * vmbus exit
189 */
190void hv_stimer_global_cleanup(void)
191{
192	int	cpu;
193	struct clock_event_device *ce;
194
195	if (ms_hyperv.features & HV_MSR_SYNTIMER_AVAILABLE) {
196		for_each_present_cpu(cpu) {
197			ce = per_cpu_ptr(hv_clock_event, cpu);
198			clockevents_unbind_device(ce, cpu);
199		}
200	}
201	hv_stimer_free();
202}
203EXPORT_SYMBOL_GPL(hv_stimer_global_cleanup);
204
205/*
206 * Code and definitions for the Hyper-V clocksources.  Two
207 * clocksources are defined: one that reads the Hyper-V defined MSR, and
208 * the other that uses the TSC reference page feature as defined in the
209 * TLFS.  The MSR version is for compatibility with old versions of
210 * Hyper-V and 32-bit x86.  The TSC reference page version is preferred.
211 */
212
213struct clocksource *hyperv_cs;
214EXPORT_SYMBOL_GPL(hyperv_cs);
215
216static struct ms_hyperv_tsc_page tsc_pg __aligned(PAGE_SIZE);
217
218struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
219{
220	return &tsc_pg;
221}
222EXPORT_SYMBOL_GPL(hv_get_tsc_page);
223
224static u64 notrace read_hv_clock_tsc(struct clocksource *arg)
225{
226	u64 current_tick = hv_read_tsc_page(&tsc_pg);
227
228	if (current_tick == U64_MAX)
229		hv_get_time_ref_count(current_tick);
230
231	return current_tick;
232}
233
234static u64 read_hv_sched_clock_tsc(void)
235{
236	return read_hv_clock_tsc(NULL) - hv_sched_clock_offset;
237}
238
239static struct clocksource hyperv_cs_tsc = {
240	.name	= "hyperv_clocksource_tsc_page",
241	.rating	= 400,
242	.read	= read_hv_clock_tsc,
243	.mask	= CLOCKSOURCE_MASK(64),
244	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
245};
246
247static u64 notrace read_hv_clock_msr(struct clocksource *arg)
248{
249	u64 current_tick;
250	/*
251	 * Read the partition counter to get the current tick count. This count
252	 * is set to 0 when the partition is created and is incremented in
253	 * 100 nanosecond units.
254	 */
255	hv_get_time_ref_count(current_tick);
256	return current_tick;
257}
258
259static u64 read_hv_sched_clock_msr(void)
260{
261	return read_hv_clock_msr(NULL) - hv_sched_clock_offset;
262}
263
264static struct clocksource hyperv_cs_msr = {
265	.name	= "hyperv_clocksource_msr",
266	.rating	= 400,
267	.read	= read_hv_clock_msr,
268	.mask	= CLOCKSOURCE_MASK(64),
269	.flags	= CLOCK_SOURCE_IS_CONTINUOUS,
270};
271
272static bool __init hv_init_tsc_clocksource(void)
273{
274	u64		tsc_msr;
275	phys_addr_t	phys_addr;
276
277	if (!(ms_hyperv.features & HV_MSR_REFERENCE_TSC_AVAILABLE))
278		return false;
279
280	hyperv_cs = &hyperv_cs_tsc;
281	phys_addr = virt_to_phys(&tsc_pg);
282
283	/*
284	 * The Hyper-V TLFS specifies to preserve the value of reserved
285	 * bits in registers. So read the existing value, preserve the
286	 * low order 12 bits, and add in the guest physical address
287	 * (which already has at least the low 12 bits set to zero since
288	 * it is page aligned). Also set the "enable" bit, which is bit 0.
289	 */
290	hv_get_reference_tsc(tsc_msr);
291	tsc_msr &= GENMASK_ULL(11, 0);
292	tsc_msr = tsc_msr | 0x1 | (u64)phys_addr;
293	hv_set_reference_tsc(tsc_msr);
294
295	hv_set_clocksource_vdso(hyperv_cs_tsc);
296	clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
297
298	hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
299	hv_setup_sched_clock(read_hv_sched_clock_tsc);
300
301	return true;
302}
303
304void __init hv_init_clocksource(void)
305{
306	/*
307	 * Try to set up the TSC page clocksource. If it succeeds, we're
308	 * done. Otherwise, set up the MSR clocksoruce.  At least one of
309	 * these will always be available except on very old versions of
310	 * Hyper-V on x86.  In that case we won't have a Hyper-V
311	 * clocksource, but Linux will still run with a clocksource based
312	 * on the emulated PIT or LAPIC timer.
313	 */
314	if (hv_init_tsc_clocksource())
315		return;
316
317	if (!(ms_hyperv.features & HV_MSR_TIME_REF_COUNT_AVAILABLE))
318		return;
319
320	hyperv_cs = &hyperv_cs_msr;
321	clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);
322
323	hv_sched_clock_offset = hyperv_cs->read(hyperv_cs);
324	hv_setup_sched_clock(read_hv_sched_clock_msr);
325}
326EXPORT_SYMBOL_GPL(hv_init_clocksource);