Commit | Line | Data |
---|---|---|
7af192c9 GH |
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> | |
71056ae2 MT |
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> | |
7af192c9 GH |
25 | #include <asm/pvclock.h> |
26 | ||
424c32f1 GC |
27 | static u8 valid_flags __read_mostly = 0; |
28 | ||
29 | void pvclock_set_flags(u8 flags) | |
30 | { | |
31 | valid_flags = flags; | |
32 | } | |
33 | ||
3807f345 GC |
34 | unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src) |
35 | { | |
a0854600 | 36 | u64 pv_tsc_khz = 1000000ULL << 32; |
3807f345 | 37 | |
a0854600 | 38 | do_div(pv_tsc_khz, src->tsc_to_system_mul); |
3807f345 | 39 | if (src->tsc_shift < 0) |
a0854600 | 40 | pv_tsc_khz <<= -src->tsc_shift; |
3807f345 | 41 | else |
a0854600 HH |
42 | pv_tsc_khz >>= src->tsc_shift; |
43 | return pv_tsc_khz; | |
3807f345 GC |
44 | } |
45 | ||
d63285e9 MT |
46 | void pvclock_touch_watchdogs(void) |
47 | { | |
48 | touch_softlockup_watchdog_sync(); | |
49 | clocksource_touch_watchdog(); | |
50 | rcu_cpu_stall_reset(); | |
8b414521 | 51 | reset_hung_task_detector(); |
d63285e9 MT |
52 | } |
53 | ||
489fb490 GC |
54 | static atomic64_t last_value = ATOMIC64_INIT(0); |
55 | ||
e7a3481c JF |
56 | void pvclock_resume(void) |
57 | { | |
58 | atomic64_set(&last_value, 0); | |
59 | } | |
60 | ||
2697902b MT |
61 | u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src) |
62 | { | |
63 | unsigned version; | |
64 | cycle_t ret; | |
65 | u8 flags; | |
66 | ||
67 | do { | |
68 | version = __pvclock_read_cycles(src, &ret, &flags); | |
69 | } while ((src->version & 1) || version != src->version); | |
70 | ||
71 | return flags & valid_flags; | |
72 | } | |
73 | ||
7af192c9 GH |
74 | cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) |
75 | { | |
7af192c9 | 76 | unsigned version; |
dce2db0a | 77 | cycle_t ret; |
489fb490 | 78 | u64 last; |
42b5637d | 79 | u8 flags; |
7af192c9 GH |
80 | |
81 | do { | |
dce2db0a | 82 | version = __pvclock_read_cycles(src, &ret, &flags); |
42b5637d | 83 | } while ((src->version & 1) || version != src->version); |
7af192c9 | 84 | |
d63285e9 MT |
85 | if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) { |
86 | src->flags &= ~PVCLOCK_GUEST_STOPPED; | |
87 | pvclock_touch_watchdogs(); | |
88 | } | |
89 | ||
3a0d7256 | 90 | if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && |
42b5637d | 91 | (flags & PVCLOCK_TSC_STABLE_BIT)) |
3a0d7256 GC |
92 | return ret; |
93 | ||
489fb490 GC |
94 | /* |
95 | * Assumption here is that last_value, a global accumulator, always goes | |
96 | * forward. If we are less than that, we should not be much smaller. | |
97 | * We assume there is an error marging we're inside, and then the correction | |
98 | * does not sacrifice accuracy. | |
99 | * | |
100 | * For reads: global may have changed between test and return, | |
101 | * but this means someone else updated poked the clock at a later time. | |
102 | * We just need to make sure we are not seeing a backwards event. | |
103 | * | |
104 | * For updates: last_value = ret is not enough, since two vcpus could be | |
105 | * updating at the same time, and one of them could be slightly behind, | |
106 | * making the assumption that last_value always go forward fail to hold. | |
107 | */ | |
108 | last = atomic64_read(&last_value); | |
109 | do { | |
110 | if (ret < last) | |
111 | return last; | |
112 | last = atomic64_cmpxchg(&last_value, last, ret); | |
113 | } while (unlikely(last != ret)); | |
114 | ||
7af192c9 GH |
115 | return ret; |
116 | } | |
117 | ||
118 | void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock, | |
119 | struct pvclock_vcpu_time_info *vcpu_time, | |
120 | struct timespec *ts) | |
121 | { | |
122 | u32 version; | |
123 | u64 delta; | |
124 | struct timespec now; | |
125 | ||
126 | /* get wallclock at system boot */ | |
127 | do { | |
128 | version = wall_clock->version; | |
129 | rmb(); /* fetch version before time */ | |
130 | now.tv_sec = wall_clock->sec; | |
131 | now.tv_nsec = wall_clock->nsec; | |
132 | rmb(); /* fetch time before checking version */ | |
133 | } while ((wall_clock->version & 1) || (version != wall_clock->version)); | |
134 | ||
135 | delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */ | |
136 | delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec; | |
137 | ||
138 | now.tv_nsec = do_div(delta, NSEC_PER_SEC); | |
139 | now.tv_sec = delta; | |
140 | ||
141 | set_normalized_timespec(ts, now.tv_sec, now.tv_nsec); | |
142 | } |