[mirror_ubuntu-zesty-kernel.git] / arch / i386 / xen / time.c

/*
 * Xen time implementation.
 *
 * This is implemented in terms of a clocksource driver which uses
 * the hypervisor clock as a nanosecond timebase, and a clockevent
 * driver which uses the hypervisor's timer mechanism.
 *
 * Jeremy Fitzhardinge <jeremy@xensource.com>, XenSource Inc, 2007
 */
#include <linux/kernel.h>
#include <linux/interrupt.h>
#include <linux/clocksource.h>
#include <linux/clockchips.h>

#include <asm/xen/hypervisor.h>
#include <asm/xen/hypercall.h>

#include <xen/events.h>
#include <xen/interface/xen.h>
#include <xen/interface/vcpu.h>

#include "xen-ops.h"

#define XEN_SHIFT 22

/* Xen may fire a timer up to this many ns early */
#define TIMER_SLOP	100000

/* These are perodically updated in shared_info, and then copied here. */
struct shadow_time_info {
	u64 tsc_timestamp;     /* TSC at last update of time vals.  */
	u64 system_timestamp;  /* Time, in nanosecs, since boot.    */
	u32 tsc_to_nsec_mul;
	int tsc_shift;
	u32 version;
};

static DEFINE_PER_CPU(struct shadow_time_info, shadow_time);

unsigned long xen_cpu_khz(void)
{
	u64 cpu_khz = 1000000ULL << 32;
	const struct vcpu_time_info *info =
		&HYPERVISOR_shared_info->vcpu_info[0].time;

	do_div(cpu_khz, info->tsc_to_system_mul);
	if (info->tsc_shift < 0)
		cpu_khz <<= -info->tsc_shift;
	else
		cpu_khz >>= info->tsc_shift;

	return cpu_khz;
}

/*
 * Reads a consistent set of time-base values from Xen, into a shadow data
 * area.
 */
static void get_time_values_from_xen(void)
{
	struct vcpu_time_info   *src;
	struct shadow_time_info *dst;

	preempt_disable();

	/* src is shared memory with the hypervisor, so we need to
	   make sure we get a consistent snapshot, even in the face of
	   being preempted. */
	src = &__get_cpu_var(xen_vcpu)->time;
	dst = &__get_cpu_var(shadow_time);

	do {
		dst->version = src->version;
		rmb();		/* fetch version before data */
		dst->tsc_timestamp     = src->tsc_timestamp;
		dst->system_timestamp  = src->system_time;
		dst->tsc_to_nsec_mul   = src->tsc_to_system_mul;
		dst->tsc_shift         = src->tsc_shift;
		rmb();		/* test version after fetching data */
	} while ((src->version & 1) | (dst->version ^ src->version));

	preempt_enable();
}

/*
 * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
 * yielding a 64-bit result.
 */
static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
{
	u64 product;
#ifdef __i386__
	u32 tmp1, tmp2;
#endif

	if (shift < 0)
		delta >>= -shift;
	else
		delta <<= shift;

#ifdef __i386__
	__asm__ (
		"mul  %5       ; "
		"mov  %4,%%eax ; "
		"mov  %%edx,%4 ; "
		"mul  %5       ; "
		"xor  %5,%5    ; "
		"add  %4,%%eax ; "
		"adc  %5,%%edx ; "
		: "=A" (product), "=r" (tmp1), "=r" (tmp2)
		: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
#elif __x86_64__
	__asm__ (
		"mul %%rdx ; shrd $32,%%rdx,%%rax"
		: "=a" (product) : "0" (delta), "d" ((u64)mul_frac) );
#else
#error implement me!
#endif

	return product;
}

static u64 get_nsec_offset(struct shadow_time_info *shadow)
{
	u64 now, delta;
	rdtscll(now);
	delta = now - shadow->tsc_timestamp;
	return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
}

cycle_t xen_clocksource_read(void)
{
	struct shadow_time_info *shadow = &get_cpu_var(shadow_time);
	cycle_t ret;

	get_time_values_from_xen();

	ret = shadow->system_timestamp + get_nsec_offset(shadow);

	put_cpu_var(shadow_time);

	return ret;
}

static void xen_read_wallclock(struct timespec *ts)
{
	const struct shared_info *s = HYPERVISOR_shared_info;
	u32 version;
	u64 delta;
	struct timespec now;

	/* get wallclock at system boot */
	do {
		version = s->wc_version;
		rmb();		/* fetch version before time */
		now.tv_sec  = s->wc_sec;
		now.tv_nsec = s->wc_nsec;
		rmb();		/* fetch time before checking version */
	} while ((s->wc_version & 1) | (version ^ s->wc_version));

	delta = xen_clocksource_read();	/* time since system boot */
	delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;

	now.tv_nsec = do_div(delta, NSEC_PER_SEC);
	now.tv_sec = delta;

	set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
}

unsigned long xen_get_wallclock(void)
{
	struct timespec ts;

	xen_read_wallclock(&ts);

	return ts.tv_sec;
}

int xen_set_wallclock(unsigned long now)
{
	/* do nothing for domU */
	return -1;
}

static struct clocksource xen_clocksource __read_mostly = {
	.name = "xen",
	.rating = 400,
	.read = xen_clocksource_read,
	.mask = ~0,
	.mult = 1<<XEN_SHIFT,		/* time directly in nanoseconds */
	.shift = XEN_SHIFT,
	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};

/*
   Xen clockevent implementation

   Xen has two clockevent implementations:

   The old timer_op one works with all released versions of Xen prior
   to version 3.0.4.  This version of the hypervisor provides a
   single-shot timer with nanosecond resolution.  However, sharing the
   same event channel is a 100Hz tick which is delivered while the
   vcpu is running.  We don't care about or use this tick, but it will
   cause the core time code to think the timer fired too soon, and
   will end up resetting it each time.  It could be filtered, but
   doing so has complications when the ktime clocksource is not yet
   the xen clocksource (ie, at boot time).

   The new vcpu_op-based timer interface allows the tick timer period
   to be changed or turned off.  The tick timer is not useful as a
   periodic timer because events are only delivered to running vcpus.
   The one-shot timer can report when a timeout is in the past, so
   set_next_event is capable of returning -ETIME when appropriate.
   This interface is used when available.
*/


/*
  Get a hypervisor absolute time.  In theory we could maintain an
  offset between the kernel's time and the hypervisor's time, and
  apply that to a kernel's absolute timeout.  Unfortunately the
  hypervisor and kernel times can drift even if the kernel is using
  the Xen clocksource, because ntp can warp the kernel's clocksource.
*/
static s64 get_abs_timeout(unsigned long delta)
{
	return xen_clocksource_read() + delta;
}

static void xen_timerop_set_mode(enum clock_event_mode mode,
				 struct clock_event_device *evt)
{
	switch (mode) {
	case CLOCK_EVT_MODE_PERIODIC:
		/* unsupported */
		WARN_ON(1);
		break;

	case CLOCK_EVT_MODE_ONESHOT:
		break;

	case CLOCK_EVT_MODE_UNUSED:
	case CLOCK_EVT_MODE_SHUTDOWN:
		HYPERVISOR_set_timer_op(0);  /* cancel timeout */
		break;
	}
}

static int xen_timerop_set_next_event(unsigned long delta,
				      struct clock_event_device *evt)
{
	WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT);

	if (HYPERVISOR_set_timer_op(get_abs_timeout(delta)) < 0)
		BUG();

	/* We may have missed the deadline, but there's no real way of
	   knowing for sure.  If the event was in the past, then we'll
	   get an immediate interrupt. */

	return 0;
}

static const struct clock_event_device xen_timerop_clockevent = {
	.name = "xen",
	.features = CLOCK_EVT_FEAT_ONESHOT,

	.max_delta_ns = 0xffffffff,
	.min_delta_ns = TIMER_SLOP,

	.mult = 1,
	.shift = 0,
	.rating = 500,

	.set_mode = xen_timerop_set_mode,
	.set_next_event = xen_timerop_set_next_event,
};


static void xen_vcpuop_set_mode(enum clock_event_mode mode,
				struct clock_event_device *evt)
{
	int cpu = smp_processor_id();

	switch (mode) {
	case CLOCK_EVT_MODE_PERIODIC:
		WARN_ON(1);	/* unsupported */
		break;

	case CLOCK_EVT_MODE_ONESHOT:
		if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL))
			BUG();
		break;

	case CLOCK_EVT_MODE_UNUSED:
	case CLOCK_EVT_MODE_SHUTDOWN:
		if (HYPERVISOR_vcpu_op(VCPUOP_stop_singleshot_timer, cpu, NULL) ||
		    HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL))
			BUG();
		break;
	}
}

static int xen_vcpuop_set_next_event(unsigned long delta,
				     struct clock_event_device *evt)
{
	int cpu = smp_processor_id();
	struct vcpu_set_singleshot_timer single;
	int ret;

	WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT);

	single.timeout_abs_ns = get_abs_timeout(delta);
	single.flags = VCPU_SSHOTTMR_future;

	ret = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, cpu, &single);

	BUG_ON(ret != 0 && ret != -ETIME);

	return ret;
}

static const struct clock_event_device xen_vcpuop_clockevent = {
	.name = "xen",
	.features = CLOCK_EVT_FEAT_ONESHOT,

	.max_delta_ns = 0xffffffff,
	.min_delta_ns = TIMER_SLOP,

	.mult = 1,
	.shift = 0,
	.rating = 500,

	.set_mode = xen_vcpuop_set_mode,
	.set_next_event = xen_vcpuop_set_next_event,
};

static const struct clock_event_device *xen_clockevent =
	&xen_timerop_clockevent;
static DEFINE_PER_CPU(struct clock_event_device, xen_clock_events);

static irqreturn_t xen_timer_interrupt(int irq, void *dev_id)
{
	struct clock_event_device *evt = &__get_cpu_var(xen_clock_events);
	irqreturn_t ret;

	ret = IRQ_NONE;
	if (evt->event_handler) {
		evt->event_handler(evt);
		ret = IRQ_HANDLED;
	}

	return ret;
}

static void xen_setup_timer(int cpu)
{
	const char *name;
	struct clock_event_device *evt;
	int irq;

	printk(KERN_INFO "installing Xen timer for CPU %d\n", cpu);

	name = kasprintf(GFP_KERNEL, "timer%d", cpu);
	if (!name)
		name = "<timer kasprintf failed>";

	irq = bind_virq_to_irqhandler(VIRQ_TIMER, cpu, xen_timer_interrupt,
				      IRQF_DISABLED|IRQF_PERCPU|IRQF_NOBALANCING,
				      name, NULL);

	evt = &get_cpu_var(xen_clock_events);
	memcpy(evt, xen_clockevent, sizeof(*evt));

	evt->cpumask = cpumask_of_cpu(cpu);
	evt->irq = irq;
	clockevents_register_device(evt);

	put_cpu_var(xen_clock_events);
}

__init void xen_time_init(void)
{
	int cpu = smp_processor_id();

	get_time_values_from_xen();

	clocksource_register(&xen_clocksource);

	if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) {
		/* Successfully turned off 100hz tick, so we have the
		   vcpuop-based timer interface */
		printk(KERN_DEBUG "Xen: using vcpuop timer interface\n");
		xen_clockevent = &xen_vcpuop_clockevent;
	}

	/* Set initial system time with full resolution */
	xen_read_wallclock(&xtime);
	set_normalized_timespec(&wall_to_monotonic,
				-xtime.tv_sec, -xtime.tv_nsec);

	tsc_disable = 0;

	xen_setup_timer(cpu);
}
Commit	Line	Data
15c84731 JF	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>
	14
	15	#include <asm/xen/hypervisor.h>
	16	#include <asm/xen/hypercall.h>
	17
	18	#include <xen/events.h>
	19	#include <xen/interface/xen.h>
	20	#include <xen/interface/vcpu.h>
	21
	22	#include "xen-ops.h"
	23
	24	#define XEN_SHIFT 22
	25
	26	/* Xen may fire a timer up to this many ns early */
	27	#define TIMER_SLOP 100000
	28
	29	/* These are perodically updated in shared_info, and then copied here. */
	30	struct shadow_time_info {
	31	u64 tsc_timestamp; /* TSC at last update of time vals. */
	32	u64 system_timestamp; /* Time, in nanosecs, since boot. */
	33	u32 tsc_to_nsec_mul;
	34	int tsc_shift;
	35	u32 version;
	36	};
	37
	38	static DEFINE_PER_CPU(struct shadow_time_info, shadow_time);
	39
	40	unsigned long xen_cpu_khz(void)
	41	{
	42	u64 cpu_khz = 1000000ULL << 32;
	43	const struct vcpu_time_info *info =
	44	&HYPERVISOR_shared_info->vcpu_info[0].time;
	45
	46	do_div(cpu_khz, info->tsc_to_system_mul);
	47	if (info->tsc_shift < 0)
	48	cpu_khz <<= -info->tsc_shift;
	49	else
	50	cpu_khz >>= info->tsc_shift;
	51
	52	return cpu_khz;
	53	}
	54
	55	/*
	56	* Reads a consistent set of time-base values from Xen, into a shadow data
	57	* area.
	58	*/
	59	static void get_time_values_from_xen(void)
	60	{
	61	struct vcpu_time_info *src;
	62	struct shadow_time_info *dst;
	63
	64	preempt_disable();
65
66	/* src is shared memory with the hypervisor, so we need to
67	make sure we get a consistent snapshot, even in the face of
68	being preempted. */
69	src = &__get_cpu_var(xen_vcpu)->time;
70	dst = &__get_cpu_var(shadow_time);
71
72	do {
73	dst->version = src->version;
74	rmb(); /* fetch version before data */
75	dst->tsc_timestamp = src->tsc_timestamp;
76	dst->system_timestamp = src->system_time;
77	dst->tsc_to_nsec_mul = src->tsc_to_system_mul;
78	dst->tsc_shift = src->tsc_shift;
79	rmb(); /* test version after fetching data */
80	} while ((src->version & 1) \| (dst->version ^ src->version));
81
82	preempt_enable();
83	}
84
85	/*
86	* Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction,
87	* yielding a 64-bit result.
88	*/
89	static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift)
90	{
91	u64 product;
92	#ifdef __i386__
93	u32 tmp1, tmp2;
94	#endif
95
96	if (shift < 0)
97	delta >>= -shift;
98	else
99	delta <<= shift;
100
101	#ifdef __i386__
102	__asm__ (
103	"mul %5 ; "
104	"mov %4,%%eax ; "
105	"mov %%edx,%4 ; "
106	"mul %5 ; "
107	"xor %5,%5 ; "
108	"add %4,%%eax ; "
109	"adc %5,%%edx ; "
110	: "=A" (product), "=r" (tmp1), "=r" (tmp2)
111	: "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) );
112	#elif __x86_64__
113	__asm__ (
114	"mul %%rdx ; shrd $32,%%rdx,%%rax"
115	: "=a" (product) : "0" (delta), "d" ((u64)mul_frac) );
116	#else
117	#error implement me!
118	#endif
119
120	return product;
121	}
122
123	static u64 get_nsec_offset(struct shadow_time_info *shadow)
124	{
125	u64 now, delta;
126	rdtscll(now);
127	delta = now - shadow->tsc_timestamp;
128	return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift);
129	}
130
131	cycle_t xen_clocksource_read(void)
132	{
133	struct shadow_time_info *shadow = &get_cpu_var(shadow_time);
134	cycle_t ret;
135
136	get_time_values_from_xen();
137
138	ret = shadow->system_timestamp + get_nsec_offset(shadow);
139
140	put_cpu_var(shadow_time);
141
142	return ret;
143	}
144
145	static void xen_read_wallclock(struct timespec *ts)
146	{
147	const struct shared_info *s = HYPERVISOR_shared_info;
148	u32 version;
149	u64 delta;
150	struct timespec now;
151
152	/* get wallclock at system boot */
153	do {
154	version = s->wc_version;
155	rmb(); /* fetch version before time */
156	now.tv_sec = s->wc_sec;
157	now.tv_nsec = s->wc_nsec;
158	rmb(); /* fetch time before checking version */
159	} while ((s->wc_version & 1) \| (version ^ s->wc_version));
160
161	delta = xen_clocksource_read(); /* time since system boot */
162	delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
163
164	now.tv_nsec = do_div(delta, NSEC_PER_SEC);
165	now.tv_sec = delta;
166
167	set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
168	}
169
170	unsigned long xen_get_wallclock(void)
171	{
172	struct timespec ts;
173
174	xen_read_wallclock(&ts);
175
176	return ts.tv_sec;
177	}
178
179	int xen_set_wallclock(unsigned long now)
180	{
181	/* do nothing for domU */
182	return -1;
183	}
184
185	static struct clocksource xen_clocksource __read_mostly = {
186	.name = "xen",
187	.rating = 400,
188	.read = xen_clocksource_read,
189	.mask = ~0,
190	.mult = 1<<XEN_SHIFT, /* time directly in nanoseconds */
191	.shift = XEN_SHIFT,
192	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
193	};
194
195	/*
196	Xen clockevent implementation
197
198	Xen has two clockevent implementations:
199
200	The old timer_op one works with all released versions of Xen prior
201	to version 3.0.4. This version of the hypervisor provides a
202	single-shot timer with nanosecond resolution. However, sharing the
203	same event channel is a 100Hz tick which is delivered while the
204	vcpu is running. We don't care about or use this tick, but it will
205	cause the core time code to think the timer fired too soon, and
206	will end up resetting it each time. It could be filtered, but
207	doing so has complications when the ktime clocksource is not yet
208	the xen clocksource (ie, at boot time).
209
210	The new vcpu_op-based timer interface allows the tick timer period
211	to be changed or turned off. The tick timer is not useful as a
212	periodic timer because events are only delivered to running vcpus.
213	The one-shot timer can report when a timeout is in the past, so
214	set_next_event is capable of returning -ETIME when appropriate.
215	This interface is used when available.
216	*/
217
218
219	/*
220	Get a hypervisor absolute time. In theory we could maintain an
221	offset between the kernel's time and the hypervisor's time, and
222	apply that to a kernel's absolute timeout. Unfortunately the
223	hypervisor and kernel times can drift even if the kernel is using
224	the Xen clocksource, because ntp can warp the kernel's clocksource.
225	*/
226	static s64 get_abs_timeout(unsigned long delta)
227	{
228	return xen_clocksource_read() + delta;
229	}
230
231	static void xen_timerop_set_mode(enum clock_event_mode mode,
232	struct clock_event_device *evt)
233	{
234	switch (mode) {
235	case CLOCK_EVT_MODE_PERIODIC:
236	/* unsupported */
237	WARN_ON(1);
238	break;
239
240	case CLOCK_EVT_MODE_ONESHOT:
241	break;
242
243	case CLOCK_EVT_MODE_UNUSED:
244	case CLOCK_EVT_MODE_SHUTDOWN:
245	HYPERVISOR_set_timer_op(0); /* cancel timeout */
246	break;
247	}
248	}
249
250	static int xen_timerop_set_next_event(unsigned long delta,
251	struct clock_event_device *evt)
252	{
253	WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT);
254
255	if (HYPERVISOR_set_timer_op(get_abs_timeout(delta)) < 0)
256	BUG();
257
258	/* We may have missed the deadline, but there's no real way of
259	knowing for sure. If the event was in the past, then we'll
260	get an immediate interrupt. */
261
262	return 0;
263	}
264
265	static const struct clock_event_device xen_timerop_clockevent = {
266	.name = "xen",
267	.features = CLOCK_EVT_FEAT_ONESHOT,
268
269	.max_delta_ns = 0xffffffff,
270	.min_delta_ns = TIMER_SLOP,
271
272	.mult = 1,
273	.shift = 0,
274	.rating = 500,
275
276	.set_mode = xen_timerop_set_mode,
277	.set_next_event = xen_timerop_set_next_event,
278	};
279
280
281
282	static void xen_vcpuop_set_mode(enum clock_event_mode mode,
283	struct clock_event_device *evt)
284	{
285	int cpu = smp_processor_id();
286
287	switch (mode) {
288	case CLOCK_EVT_MODE_PERIODIC:
289	WARN_ON(1); /* unsupported */
290	break;
291
292	case CLOCK_EVT_MODE_ONESHOT:
293	if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL))
294	BUG();
295	break;
296
297	case CLOCK_EVT_MODE_UNUSED:
298	case CLOCK_EVT_MODE_SHUTDOWN:
299	if (HYPERVISOR_vcpu_op(VCPUOP_stop_singleshot_timer, cpu, NULL) \|\|
300	HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL))
301	BUG();
302	break;
303	}
304	}
305
306	static int xen_vcpuop_set_next_event(unsigned long delta,
307	struct clock_event_device *evt)
308	{
309	int cpu = smp_processor_id();
310	struct vcpu_set_singleshot_timer single;
311	int ret;
312
313	WARN_ON(evt->mode != CLOCK_EVT_MODE_ONESHOT);
314
315	single.timeout_abs_ns = get_abs_timeout(delta);
316	single.flags = VCPU_SSHOTTMR_future;
317
318	ret = HYPERVISOR_vcpu_op(VCPUOP_set_singleshot_timer, cpu, &single);
319
320	BUG_ON(ret != 0 && ret != -ETIME);
321
322	return ret;
323	}
324
325	static const struct clock_event_device xen_vcpuop_clockevent = {
326	.name = "xen",
327	.features = CLOCK_EVT_FEAT_ONESHOT,
328
329	.max_delta_ns = 0xffffffff,
330	.min_delta_ns = TIMER_SLOP,
331
332	.mult = 1,
333	.shift = 0,
334	.rating = 500,
335
336	.set_mode = xen_vcpuop_set_mode,
337	.set_next_event = xen_vcpuop_set_next_event,
338	};
339
340	static const struct clock_event_device *xen_clockevent =
341	&xen_timerop_clockevent;
342	static DEFINE_PER_CPU(struct clock_event_device, xen_clock_events);
343
344	static irqreturn_t xen_timer_interrupt(int irq, void *dev_id)
345	{
346	struct clock_event_device *evt = &__get_cpu_var(xen_clock_events);
347	irqreturn_t ret;
348
349	ret = IRQ_NONE;
350	if (evt->event_handler) {
351	evt->event_handler(evt);
352	ret = IRQ_HANDLED;
353	}
354
355	return ret;
356	}
357
358	static void xen_setup_timer(int cpu)
359	{
360	const char *name;
361	struct clock_event_device *evt;
362	int irq;
363
364	printk(KERN_INFO "installing Xen timer for CPU %d\n", cpu);
365
366	name = kasprintf(GFP_KERNEL, "timer%d", cpu);
367	if (!name)
368	name = "<timer kasprintf failed>";
369
370	irq = bind_virq_to_irqhandler(VIRQ_TIMER, cpu, xen_timer_interrupt,
371	IRQF_DISABLED\|IRQF_PERCPU\|IRQF_NOBALANCING,
372	name, NULL);
373
374	evt = &get_cpu_var(xen_clock_events);
375	memcpy(evt, xen_clockevent, sizeof(*evt));
376
377	evt->cpumask = cpumask_of_cpu(cpu);
378	evt->irq = irq;
379	clockevents_register_device(evt);
380
381	put_cpu_var(xen_clock_events);
382	}
383
384	__init void xen_time_init(void)
385	{
386	int cpu = smp_processor_id();
387
388	get_time_values_from_xen();
389
390	clocksource_register(&xen_clocksource);
391
392	if (HYPERVISOR_vcpu_op(VCPUOP_stop_periodic_timer, cpu, NULL) == 0) {
393	/* Successfully turned off 100hz tick, so we have the
394	vcpuop-based timer interface */
395	printk(KERN_DEBUG "Xen: using vcpuop timer interface\n");
396	xen_clockevent = &xen_vcpuop_clockevent;
397	}
398
399	/* Set initial system time with full resolution */
400	xen_read_wallclock(&xtime);
401	set_normalized_timespec(&wall_to_monotonic,
402	-xtime.tv_sec, -xtime.tv_nsec);
403
404	tsc_disable = 0;
405
406	xen_setup_timer(cpu);
407	}