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1/* paravirtual clock -- common code used by kvm/xen
2
3 This program is free software; you can redistribute it and/or modify
4 it under the terms of the GNU General Public License as published by
5 the Free Software Foundation; either version 2 of the License, or
6 (at your option) any later version.
7
8 This program is distributed in the hope that it will be useful,
9 but WITHOUT ANY WARRANTY; without even the implied warranty of
10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 GNU General Public License for more details.
12
13 You should have received a copy of the GNU General Public License
14 along with this program; if not, write to the Free Software
15 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
16*/
17
18#include <linux/kernel.h>
19#include <linux/percpu.h>
20#include <linux/notifier.h>
21#include <linux/sched.h>
22#include <linux/gfp.h>
23#include <linux/bootmem.h>
24#include <linux/nmi.h>
25
26#include <asm/fixmap.h>
27#include <asm/pvclock.h>
28#include <asm/vgtod.h>
29
30static u8 valid_flags __read_mostly = 0;
31static struct pvclock_vsyscall_time_info *pvti_cpu0_va __read_mostly;
32
33void pvclock_set_flags(u8 flags)
34{
35 valid_flags = flags;
36}
37
38unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
39{
40 u64 pv_tsc_khz = 1000000ULL << 32;
41
42 do_div(pv_tsc_khz, src->tsc_to_system_mul);
43 if (src->tsc_shift < 0)
44 pv_tsc_khz <<= -src->tsc_shift;
45 else
46 pv_tsc_khz >>= src->tsc_shift;
47 return pv_tsc_khz;
48}
49
50void pvclock_touch_watchdogs(void)
51{
52 touch_softlockup_watchdog_sync();
53 clocksource_touch_watchdog();
54 rcu_cpu_stall_reset();
55 reset_hung_task_detector();
56}
57
58static atomic64_t last_value = ATOMIC64_INIT(0);
59
60void pvclock_resume(void)
61{
62 atomic64_set(&last_value, 0);
63}
64
65u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
66{
67 unsigned version;
68 u8 flags;
69
70 do {
71 version = pvclock_read_begin(src);
72 flags = src->flags;
73 } while (pvclock_read_retry(src, version));
74
75 return flags & valid_flags;
76}
77
78u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
79{
80 unsigned version;
81 u64 ret;
82 u64 last;
83 u8 flags;
84
85 do {
86 version = pvclock_read_begin(src);
87 ret = __pvclock_read_cycles(src, rdtsc_ordered());
88 flags = src->flags;
89 } while (pvclock_read_retry(src, version));
90
91 if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
92 src->flags &= ~PVCLOCK_GUEST_STOPPED;
93 pvclock_touch_watchdogs();
94 }
95
96 if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
97 (flags & PVCLOCK_TSC_STABLE_BIT))
98 return ret;
99
100 /*
101 * Assumption here is that last_value, a global accumulator, always goes
102 * forward. If we are less than that, we should not be much smaller.
103 * We assume there is an error marging we're inside, and then the correction
104 * does not sacrifice accuracy.
105 *
106 * For reads: global may have changed between test and return,
107 * but this means someone else updated poked the clock at a later time.
108 * We just need to make sure we are not seeing a backwards event.
109 *
110 * For updates: last_value = ret is not enough, since two vcpus could be
111 * updating at the same time, and one of them could be slightly behind,
112 * making the assumption that last_value always go forward fail to hold.
113 */
114 last = atomic64_read(&last_value);
115 do {
116 if (ret < last)
117 return last;
118 last = atomic64_cmpxchg(&last_value, last, ret);
119 } while (unlikely(last != ret));
120
121 return ret;
122}
123
124void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
125 struct pvclock_vcpu_time_info *vcpu_time,
126 struct timespec *ts)
127{
128 u32 version;
129 u64 delta;
130 struct timespec now;
131
132 /* get wallclock at system boot */
133 do {
134 version = wall_clock->version;
135 rmb(); /* fetch version before time */
136 now.tv_sec = wall_clock->sec;
137 now.tv_nsec = wall_clock->nsec;
138 rmb(); /* fetch time before checking version */
139 } while ((wall_clock->version & 1) || (version != wall_clock->version));
140
141 delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */
142 delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
143
144 now.tv_nsec = do_div(delta, NSEC_PER_SEC);
145 now.tv_sec = delta;
146
147 set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
148}
149
150void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti)
151{
152 WARN_ON(vclock_was_used(VCLOCK_PVCLOCK));
153 pvti_cpu0_va = pvti;
154}
155
156struct pvclock_vsyscall_time_info *pvclock_get_pvti_cpu0_va(void)
157{
158 return pvti_cpu0_va;
159}
160EXPORT_SYMBOL_GPL(pvclock_get_pvti_cpu0_va);
1/* paravirtual clock -- common code used by kvm/xen
2
3 This program is free software; you can redistribute it and/or modify
4 it under the terms of the GNU General Public License as published by
5 the Free Software Foundation; either version 2 of the License, or
6 (at your option) any later version.
7
8 This program is distributed in the hope that it will be useful,
9 but WITHOUT ANY WARRANTY; without even the implied warranty of
10 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
11 GNU General Public License for more details.
12
13 You should have received a copy of the GNU General Public License
14 along with this program; if not, write to the Free Software
15 Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
16*/
17
18#include <linux/kernel.h>
19#include <linux/percpu.h>
20#include <linux/notifier.h>
21#include <linux/sched.h>
22#include <linux/gfp.h>
23#include <linux/bootmem.h>
24#include <asm/fixmap.h>
25#include <asm/pvclock.h>
26
27static u8 valid_flags __read_mostly = 0;
28
29void pvclock_set_flags(u8 flags)
30{
31 valid_flags = flags;
32}
33
34unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
35{
36 u64 pv_tsc_khz = 1000000ULL << 32;
37
38 do_div(pv_tsc_khz, src->tsc_to_system_mul);
39 if (src->tsc_shift < 0)
40 pv_tsc_khz <<= -src->tsc_shift;
41 else
42 pv_tsc_khz >>= src->tsc_shift;
43 return pv_tsc_khz;
44}
45
46void pvclock_touch_watchdogs(void)
47{
48 touch_softlockup_watchdog_sync();
49 clocksource_touch_watchdog();
50 rcu_cpu_stall_reset();
51 reset_hung_task_detector();
52}
53
54static atomic64_t last_value = ATOMIC64_INIT(0);
55
56void pvclock_resume(void)
57{
58 atomic64_set(&last_value, 0);
59}
60
61u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
62{
63 unsigned version;
64 u8 flags;
65
66 do {
67 version = pvclock_read_begin(src);
68 flags = src->flags;
69 } while (pvclock_read_retry(src, version));
70
71 return flags & valid_flags;
72}
73
74u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
75{
76 unsigned version;
77 u64 ret;
78 u64 last;
79 u8 flags;
80
81 do {
82 version = pvclock_read_begin(src);
83 ret = __pvclock_read_cycles(src, rdtsc_ordered());
84 flags = src->flags;
85 } while (pvclock_read_retry(src, version));
86
87 if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
88 src->flags &= ~PVCLOCK_GUEST_STOPPED;
89 pvclock_touch_watchdogs();
90 }
91
92 if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
93 (flags & PVCLOCK_TSC_STABLE_BIT))
94 return ret;
95
96 /*
97 * Assumption here is that last_value, a global accumulator, always goes
98 * forward. If we are less than that, we should not be much smaller.
99 * We assume there is an error marging we're inside, and then the correction
100 * does not sacrifice accuracy.
101 *
102 * For reads: global may have changed between test and return,
103 * but this means someone else updated poked the clock at a later time.
104 * We just need to make sure we are not seeing a backwards event.
105 *
106 * For updates: last_value = ret is not enough, since two vcpus could be
107 * updating at the same time, and one of them could be slightly behind,
108 * making the assumption that last_value always go forward fail to hold.
109 */
110 last = atomic64_read(&last_value);
111 do {
112 if (ret < last)
113 return last;
114 last = atomic64_cmpxchg(&last_value, last, ret);
115 } while (unlikely(last != ret));
116
117 return ret;
118}
119
120void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
121 struct pvclock_vcpu_time_info *vcpu_time,
122 struct timespec *ts)
123{
124 u32 version;
125 u64 delta;
126 struct timespec now;
127
128 /* get wallclock at system boot */
129 do {
130 version = wall_clock->version;
131 rmb(); /* fetch version before time */
132 now.tv_sec = wall_clock->sec;
133 now.tv_nsec = wall_clock->nsec;
134 rmb(); /* fetch time before checking version */
135 } while ((wall_clock->version & 1) || (version != wall_clock->version));
136
137 delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */
138 delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
139
140 now.tv_nsec = do_div(delta, NSEC_PER_SEC);
141 now.tv_sec = delta;
142
143 set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
144}