[deliverable/linux.git] / arch / x86 / kernel / kvmclock.c

/*  KVM paravirtual clock driver. A clocksource implementation
    Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License as published by
    the Free Software Foundation; either version 2 of the License, or
    (at your option) any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.

    You should have received a copy of the GNU General Public License
    along with this program; if not, write to the Free Software
    Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
*/

#include <linux/clocksource.h>
#include <linux/kvm_para.h>
#include <asm/pvclock.h>
#include <asm/msr.h>
#include <asm/apic.h>
#include <linux/percpu.h>
#include <linux/hardirq.h>
#include <linux/memblock.h>
#include <linux/sched.h>

#include <asm/x86_init.h>
#include <asm/reboot.h>

static int kvmclock __ro_after_init = 1;
static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
static cycle_t kvm_sched_clock_offset;

static int parse_no_kvmclock(char *arg)
{
	kvmclock = 0;
	return 0;
}
early_param("no-kvmclock", parse_no_kvmclock);

/* The hypervisor will put information about time periodically here */
static struct pvclock_vsyscall_time_info *hv_clock;
static struct pvclock_wall_clock wall_clock;

struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
{
	return hv_clock;
}

/*
 * The wallclock is the time of day when we booted. Since then, some time may
 * have elapsed since the hypervisor wrote the data. So we try to account for
 * that with system time
 */
static void kvm_get_wallclock(struct timespec *now)
{
	struct pvclock_vcpu_time_info *vcpu_time;
	int low, high;
	int cpu;

	low = (int)__pa_symbol(&wall_clock);
	high = ((u64)__pa_symbol(&wall_clock) >> 32);

	native_write_msr(msr_kvm_wall_clock, low, high);

	cpu = get_cpu();

	vcpu_time = &hv_clock[cpu].pvti;
	pvclock_read_wallclock(&wall_clock, vcpu_time, now);

	put_cpu();
}

static int kvm_set_wallclock(const struct timespec *now)
{
	return -1;
}

static cycle_t kvm_clock_read(void)
{
	struct pvclock_vcpu_time_info *src;
	cycle_t ret;
	int cpu;

	preempt_disable_notrace();
	cpu = smp_processor_id();
	src = &hv_clock[cpu].pvti;
	ret = pvclock_clocksource_read(src);
	preempt_enable_notrace();
	return ret;
}

static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
{
	return kvm_clock_read();
}

static cycle_t kvm_sched_clock_read(void)
{
	return kvm_clock_read() - kvm_sched_clock_offset;
}

static inline void kvm_sched_clock_init(bool stable)
{
	if (!stable) {
		pv_time_ops.sched_clock = kvm_clock_read;
		return;
	}

	kvm_sched_clock_offset = kvm_clock_read();
	pv_time_ops.sched_clock = kvm_sched_clock_read;
	set_sched_clock_stable();

	printk(KERN_INFO "kvm-clock: using sched offset of %llu cycles\n",
			kvm_sched_clock_offset);

	BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) >
	         sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
}

/*
 * If we don't do that, there is the possibility that the guest
 * will calibrate under heavy load - thus, getting a lower lpj -
 * and execute the delays themselves without load. This is wrong,
 * because no delay loop can finish beforehand.
 * Any heuristics is subject to fail, because ultimately, a large
 * poll of guests can be running and trouble each other. So we preset
 * lpj here
 */
static unsigned long kvm_get_tsc_khz(void)
{
	struct pvclock_vcpu_time_info *src;
	int cpu;
	unsigned long tsc_khz;

	cpu = get_cpu();
	src = &hv_clock[cpu].pvti;
	tsc_khz = pvclock_tsc_khz(src);
	put_cpu();
	return tsc_khz;
}

static void kvm_get_preset_lpj(void)
{
	unsigned long khz;
	u64 lpj;

	khz = kvm_get_tsc_khz();

	lpj = ((u64)khz * 1000);
	do_div(lpj, HZ);
	preset_lpj = lpj;
}

bool kvm_check_and_clear_guest_paused(void)
{
	bool ret = false;
	struct pvclock_vcpu_time_info *src;
	int cpu = smp_processor_id();

	if (!hv_clock)
		return ret;

	src = &hv_clock[cpu].pvti;
	if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
		src->flags &= ~PVCLOCK_GUEST_STOPPED;
		pvclock_touch_watchdogs();
		ret = true;
	}

	return ret;
}

static struct clocksource kvm_clock = {
	.name = "kvm-clock",
	.read = kvm_clock_get_cycles,
	.rating = 400,
	.mask = CLOCKSOURCE_MASK(64),
	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
};

int kvm_register_clock(char *txt)
{
	int cpu = smp_processor_id();
	int low, high, ret;
	struct pvclock_vcpu_time_info *src;

	if (!hv_clock)
		return 0;

	src = &hv_clock[cpu].pvti;
	low = (int)slow_virt_to_phys(src) | 1;
	high = ((u64)slow_virt_to_phys(src) >> 32);
	ret = native_write_msr_safe(msr_kvm_system_time, low, high);
	printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
	       cpu, high, low, txt);

	return ret;
}

static void kvm_save_sched_clock_state(void)
{
}

static void kvm_restore_sched_clock_state(void)
{
	kvm_register_clock("primary cpu clock, resume");
}

#ifdef CONFIG_X86_LOCAL_APIC
static void kvm_setup_secondary_clock(void)
{
	/*
	 * Now that the first cpu already had this clocksource initialized,
	 * we shouldn't fail.
	 */
	WARN_ON(kvm_register_clock("secondary cpu clock"));
}
#endif

/*
 * After the clock is registered, the host will keep writing to the
 * registered memory location. If the guest happens to shutdown, this memory
 * won't be valid. In cases like kexec, in which you install a new kernel, this
 * means a random memory location will be kept being written. So before any
 * kind of shutdown from our side, we unregister the clock by writing anything
 * that does not have the 'enable' bit set in the msr
 */
#ifdef CONFIG_KEXEC_CORE
static void kvm_crash_shutdown(struct pt_regs *regs)
{
	native_write_msr(msr_kvm_system_time, 0, 0);
	kvm_disable_steal_time();
	native_machine_crash_shutdown(regs);
}
#endif

static void kvm_shutdown(void)
{
	native_write_msr(msr_kvm_system_time, 0, 0);
	kvm_disable_steal_time();
	native_machine_shutdown();
}

void __init kvmclock_init(void)
{
	struct pvclock_vcpu_time_info *vcpu_time;
	unsigned long mem;
	int size, cpu;
	u8 flags;

	size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);

	if (!kvm_para_available())
		return;

	if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
		msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
		msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
	} else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
		return;

	printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
		msr_kvm_system_time, msr_kvm_wall_clock);

	mem = memblock_alloc(size, PAGE_SIZE);
	if (!mem)
		return;
	hv_clock = __va(mem);
	memset(hv_clock, 0, size);

	if (kvm_register_clock("primary cpu clock")) {
		hv_clock = NULL;
		memblock_free(mem, size);
		return;
	}

	if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
		pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);

	cpu = get_cpu();
	vcpu_time = &hv_clock[cpu].pvti;
	flags = pvclock_read_flags(vcpu_time);

	kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
	put_cpu();

	x86_platform.calibrate_tsc = kvm_get_tsc_khz;
	x86_platform.get_wallclock = kvm_get_wallclock;
	x86_platform.set_wallclock = kvm_set_wallclock;
#ifdef CONFIG_X86_LOCAL_APIC
	x86_cpuinit.early_percpu_clock_init =
		kvm_setup_secondary_clock;
#endif
	x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
	x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
	machine_ops.shutdown  = kvm_shutdown;
#ifdef CONFIG_KEXEC_CORE
	machine_ops.crash_shutdown  = kvm_crash_shutdown;
#endif
	kvm_get_preset_lpj();
	clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
	pv_info.name = "KVM";
}

int __init kvm_setup_vsyscall_timeinfo(void)
{
#ifdef CONFIG_X86_64
	int cpu;
	u8 flags;
	struct pvclock_vcpu_time_info *vcpu_time;
	unsigned int size;

	if (!hv_clock)
		return 0;

	size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);

	cpu = get_cpu();

	vcpu_time = &hv_clock[cpu].pvti;
	flags = pvclock_read_flags(vcpu_time);

	if (!(flags & PVCLOCK_TSC_STABLE_BIT)) {
		put_cpu();
		return 1;
	}

	put_cpu();

	kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
#endif
	return 0;
}
Commit	Line	Data
790c73f6 GOC	1	/* KVM paravirtual clock driver. A clocksource implementation
	2	Copyright (C) 2008 Glauber de Oliveira Costa, Red Hat Inc.
	3
	4	This program is free software; you can redistribute it and/or modify
	5	it under the terms of the GNU General Public License as published by
	6	the Free Software Foundation; either version 2 of the License, or
	7	(at your option) any later version.
	8
	9	This program is distributed in the hope that it will be useful,
	10	but WITHOUT ANY WARRANTY; without even the implied warranty of
	11	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	12	GNU General Public License for more details.
	13
	14	You should have received a copy of the GNU General Public License
	15	along with this program; if not, write to the Free Software
	16	Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
	17	*/
	18
	19	#include <linux/clocksource.h>
	20	#include <linux/kvm_para.h>
f6e16d5a	21	#include <asm/pvclock.h>
790c73f6 GOC	22	#include <asm/msr.h>
	23	#include <asm/apic.h>
	24	#include <linux/percpu.h>
3b5d56b9	25	#include <linux/hardirq.h>
7069ed67	26	#include <linux/memblock.h>
0ad83caa	27	#include <linux/sched.h>
736decac TG	28
736decac TG	29	#include <asm/x86_init.h>
1e977aa1	30	#include <asm/reboot.h>
790c73f6	31
404f6aac	32	static int kvmclock __ro_after_init = 1;
838815a7 GC	33	static int msr_kvm_system_time = MSR_KVM_SYSTEM_TIME;
838815a7 GC	34	static int msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK;
72c930dc	35	static cycle_t kvm_sched_clock_offset;
790c73f6 GOC	36
	37	static int parse_no_kvmclock(char *arg)
	38	{
	39	kvmclock = 0;
	40	return 0;
	41	}
	42	early_param("no-kvmclock", parse_no_kvmclock);
	43
	44	/* The hypervisor will put information about time periodically here */
3dc4f7cf	45	static struct pvclock_vsyscall_time_info *hv_clock;
f6e16d5a	46	static struct pvclock_wall_clock wall_clock;
790c73f6	47
dac16fba AL	48	struct pvclock_vsyscall_time_info *pvclock_pvti_cpu0_va(void)
	49	{
	50	return hv_clock;
	51	}
	52
790c73f6 GOC	53	/*
	54	* The wallclock is the time of day when we booted. Since then, some time may
	55	* have elapsed since the hypervisor wrote the data. So we try to account for
	56	* that with system time
	57	*/
3565184e	58	static void kvm_get_wallclock(struct timespec *now)
790c73f6	59	{
f6e16d5a	60	struct pvclock_vcpu_time_info *vcpu_time;
790c73f6	61	int low, high;
7069ed67	62	int cpu;
790c73f6	63
a20316d2 GC	64	low = (int)__pa_symbol(&wall_clock);
a20316d2 GC	65	high = ((u64)__pa_symbol(&wall_clock) >> 32);
838815a7 GC	66
838815a7 GC	67	native_write_msr(msr_kvm_wall_clock, low, high);
790c73f6	68
c6338ce4	69	cpu = get_cpu();
7069ed67	70
3dc4f7cf	71	vcpu_time = &hv_clock[cpu].pvti;
3565184e	72	pvclock_read_wallclock(&wall_clock, vcpu_time, now);
7069ed67	73
c6338ce4	74	put_cpu();
790c73f6 GOC	75	}
790c73f6 GOC	76
3565184e	77	static int kvm_set_wallclock(const struct timespec *now)
790c73f6	78	{
f6e16d5a	79	return -1;
790c73f6 GOC	80	}
790c73f6 GOC	81
790c73f6 GOC	82	static cycle_t kvm_clock_read(void)
790c73f6 GOC	83	{
f6e16d5a GH	84	struct pvclock_vcpu_time_info *src;
f6e16d5a GH	85	cycle_t ret;
7069ed67	86	int cpu;
790c73f6	87
95ef1e52	88	preempt_disable_notrace();
7069ed67	89	cpu = smp_processor_id();
3dc4f7cf	90	src = &hv_clock[cpu].pvti;
f6e16d5a	91	ret = pvclock_clocksource_read(src);
95ef1e52	92	preempt_enable_notrace();
f6e16d5a	93	return ret;
790c73f6	94	}
f6e16d5a	95
8e19608e MD	96	static cycle_t kvm_clock_get_cycles(struct clocksource *cs)
	97	{
	98	return kvm_clock_read();
	99	}
	100
72c930dc RK	101	static cycle_t kvm_sched_clock_read(void)
	102	{
	103	return kvm_clock_read() - kvm_sched_clock_offset;
	104	}
	105
	106	static inline void kvm_sched_clock_init(bool stable)
	107	{
	108	if (!stable) {
	109	pv_time_ops.sched_clock = kvm_clock_read;
	110	return;
	111	}
	112
	113	kvm_sched_clock_offset = kvm_clock_read();
	114	pv_time_ops.sched_clock = kvm_sched_clock_read;
	115	set_sched_clock_stable();
	116
	117	printk(KERN_INFO "kvm-clock: using sched offset of %llu cycles\n",
	118	kvm_sched_clock_offset);
	119
	120	BUILD_BUG_ON(sizeof(kvm_sched_clock_offset) >
	121	sizeof(((struct pvclock_vcpu_time_info *)NULL)->system_time));
	122	}
	123
0293615f GC	124	/*
	125	* If we don't do that, there is the possibility that the guest
	126	* will calibrate under heavy load - thus, getting a lower lpj -
	127	* and execute the delays themselves without load. This is wrong,
	128	* because no delay loop can finish beforehand.
	129	* Any heuristics is subject to fail, because ultimately, a large
	130	* poll of guests can be running and trouble each other. So we preset
	131	* lpj here
	132	*/
	133	static unsigned long kvm_get_tsc_khz(void)
	134	{
e93353c9	135	struct pvclock_vcpu_time_info *src;
7069ed67 MT	136	int cpu;
	137	unsigned long tsc_khz;
	138
c6338ce4	139	cpu = get_cpu();
3dc4f7cf	140	src = &hv_clock[cpu].pvti;
7069ed67	141	tsc_khz = pvclock_tsc_khz(src);
c6338ce4	142	put_cpu();
7069ed67	143	return tsc_khz;
0293615f GC	144	}
	145
	146	static void kvm_get_preset_lpj(void)
	147	{
0293615f GC	148	unsigned long khz;
	149	u64 lpj;
	150
e93353c9	151	khz = kvm_get_tsc_khz();
0293615f GC	152
	153	lpj = ((u64)khz * 1000);
	154	do_div(lpj, HZ);
	155	preset_lpj = lpj;
	156	}
	157
3b5d56b9 EM	158	bool kvm_check_and_clear_guest_paused(void)
	159	{
	160	bool ret = false;
	161	struct pvclock_vcpu_time_info *src;
7069ed67 MT	162	int cpu = smp_processor_id();
	163
	164	if (!hv_clock)
	165	return ret;
3b5d56b9	166
3dc4f7cf	167	src = &hv_clock[cpu].pvti;
3b5d56b9	168	if ((src->flags & PVCLOCK_GUEST_STOPPED) != 0) {
7069ed67	169	src->flags &= ~PVCLOCK_GUEST_STOPPED;
d63285e9	170	pvclock_touch_watchdogs();
3b5d56b9 EM	171	ret = true;
	172	}
	173
	174	return ret;
	175	}
3b5d56b9	176
790c73f6 GOC	177	static struct clocksource kvm_clock = {
790c73f6 GOC	178	.name = "kvm-clock",
8e19608e	179	.read = kvm_clock_get_cycles,
790c73f6 GOC	180	.rating = 400,
790c73f6 GOC	181	.mask = CLOCKSOURCE_MASK(64),
790c73f6 GOC	182	.flags = CLOCK_SOURCE_IS_CONTINUOUS,
	183	};
	184
ca3f1017	185	int kvm_register_clock(char *txt)
790c73f6 GOC	186	{
790c73f6 GOC	187	int cpu = smp_processor_id();
19b6a85b	188	int low, high, ret;
fe1140cc JK	189	struct pvclock_vcpu_time_info *src;
	190
	191	if (!hv_clock)
	192	return 0;
19b6a85b	193
fe1140cc	194	src = &hv_clock[cpu].pvti;
5dfd486c DH	195	low = (int)slow_virt_to_phys(src) \| 1;
5dfd486c DH	196	high = ((u64)slow_virt_to_phys(src) >> 32);
19b6a85b	197	ret = native_write_msr_safe(msr_kvm_system_time, low, high);
f6e16d5a GH	198	printk(KERN_INFO "kvm-clock: cpu %d, msr %x:%x, %s\n",
f6e16d5a GH	199	cpu, high, low, txt);
838815a7	200
19b6a85b	201	return ret;
790c73f6 GOC	202	}
790c73f6 GOC	203
b74f05d6 MT	204	static void kvm_save_sched_clock_state(void)
	205	{
	206	}
	207
	208	static void kvm_restore_sched_clock_state(void)
	209	{
	210	kvm_register_clock("primary cpu clock, resume");
	211	}
	212
b8ba5f10	213	#ifdef CONFIG_X86_LOCAL_APIC
148f9bb8	214	static void kvm_setup_secondary_clock(void)
790c73f6 GOC	215	{
	216	/*
	217	* Now that the first cpu already had this clocksource initialized,
	218	* we shouldn't fail.
	219	*/
f6e16d5a	220	WARN_ON(kvm_register_clock("secondary cpu clock"));
790c73f6	221	}
b8ba5f10	222	#endif
790c73f6	223
1e977aa1 GC	224	/*
	225	* After the clock is registered, the host will keep writing to the
	226	* registered memory location. If the guest happens to shutdown, this memory
	227	* won't be valid. In cases like kexec, in which you install a new kernel, this
	228	* means a random memory location will be kept being written. So before any
6a6256f9	229	* kind of shutdown from our side, we unregister the clock by writing anything
1e977aa1 GC	230	* that does not have the 'enable' bit set in the msr
1e977aa1 GC	231	*/
2965faa5	232	#ifdef CONFIG_KEXEC_CORE
1e977aa1 GC	233	static void kvm_crash_shutdown(struct pt_regs *regs)
1e977aa1 GC	234	{
838815a7	235	native_write_msr(msr_kvm_system_time, 0, 0);
d910f5c1	236	kvm_disable_steal_time();
1e977aa1 GC	237	native_machine_crash_shutdown(regs);
	238	}
	239	#endif
	240
	241	static void kvm_shutdown(void)
	242	{
838815a7	243	native_write_msr(msr_kvm_system_time, 0, 0);
d910f5c1	244	kvm_disable_steal_time();
1e977aa1 GC	245	native_machine_shutdown();
	246	}
	247
790c73f6 GOC	248	void __init kvmclock_init(void)
790c73f6 GOC	249	{
0ad83caa	250	struct pvclock_vcpu_time_info *vcpu_time;
7069ed67	251	unsigned long mem;
0ad83caa LC	252	int size, cpu;
0ad83caa LC	253	u8 flags;
ed55705d MT	254
ed55705d MT	255	size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
7069ed67	256
790c73f6 GOC	257	if (!kvm_para_available())
	258	return;
	259
838815a7 GC	260	if (kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE2)) {
	261	msr_kvm_system_time = MSR_KVM_SYSTEM_TIME_NEW;
	262	msr_kvm_wall_clock = MSR_KVM_WALL_CLOCK_NEW;
	263	} else if (!(kvmclock && kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE)))
	264	return;
	265
	266	printk(KERN_INFO "kvm-clock: Using msrs %x and %x",
	267	msr_kvm_system_time, msr_kvm_wall_clock);
	268
ed55705d	269	mem = memblock_alloc(size, PAGE_SIZE);
7069ed67 MT	270	if (!mem)
	271	return;
	272	hv_clock = __va(mem);
07868fc6	273	memset(hv_clock, 0, size);
7069ed67	274
0d75de4a	275	if (kvm_register_clock("primary cpu clock")) {
7069ed67	276	hv_clock = NULL;
ed55705d	277	memblock_free(mem, size);
838815a7	278	return;
7069ed67	279	}
72c930dc RK	280
	281	if (kvm_para_has_feature(KVM_FEATURE_CLOCKSOURCE_STABLE_BIT))
	282	pvclock_set_flags(PVCLOCK_TSC_STABLE_BIT);
	283
	284	cpu = get_cpu();
	285	vcpu_time = &hv_clock[cpu].pvti;
	286	flags = pvclock_read_flags(vcpu_time);
	287
	288	kvm_sched_clock_init(flags & PVCLOCK_TSC_STABLE_BIT);
	289	put_cpu();
	290
838815a7 GC	291	x86_platform.calibrate_tsc = kvm_get_tsc_khz;
	292	x86_platform.get_wallclock = kvm_get_wallclock;
	293	x86_platform.set_wallclock = kvm_set_wallclock;
b8ba5f10	294	#ifdef CONFIG_X86_LOCAL_APIC
df156f90	295	x86_cpuinit.early_percpu_clock_init =
838815a7	296	kvm_setup_secondary_clock;
b8ba5f10	297	#endif
b74f05d6 MT	298	x86_platform.save_sched_clock_state = kvm_save_sched_clock_state;
b74f05d6 MT	299	x86_platform.restore_sched_clock_state = kvm_restore_sched_clock_state;
838815a7	300	machine_ops.shutdown = kvm_shutdown;
2965faa5	301	#ifdef CONFIG_KEXEC_CORE
838815a7	302	machine_ops.crash_shutdown = kvm_crash_shutdown;
1e977aa1	303	#endif
838815a7	304	kvm_get_preset_lpj();
b01cc1b0	305	clocksource_register_hz(&kvm_clock, NSEC_PER_SEC);
838815a7	306	pv_info.name = "KVM";
790c73f6	307	}
3dc4f7cf MT	308
	309	int __init kvm_setup_vsyscall_timeinfo(void)
	310	{
	311	#ifdef CONFIG_X86_64
	312	int cpu;
3dc4f7cf MT	313	u8 flags;
	314	struct pvclock_vcpu_time_info *vcpu_time;
	315	unsigned int size;
	316
fe1140cc JK	317	if (!hv_clock)
	318	return 0;
	319
ed55705d	320	size = PAGE_ALIGN(sizeof(struct pvclock_vsyscall_time_info)*NR_CPUS);
3dc4f7cf	321
c6338ce4	322	cpu = get_cpu();
3dc4f7cf MT	323
	324	vcpu_time = &hv_clock[cpu].pvti;
	325	flags = pvclock_read_flags(vcpu_time);
	326
	327	if (!(flags & PVCLOCK_TSC_STABLE_BIT)) {
c6338ce4	328	put_cpu();
3dc4f7cf MT	329	return 1;
	330	}
	331
c6338ce4	332	put_cpu();
3dc4f7cf MT	333
	334	kvm_clock.archdata.vclock_mode = VCLOCK_PVCLOCK;
	335	#endif
	336	return 0;
	337	}