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; | |
2697902b MT |
64 | u8 flags; |
65 | ||
66 | do { | |
3aed64f6 | 67 | version = pvclock_read_begin(src); |
ed911b43 | 68 | flags = src->flags; |
3aed64f6 | 69 | } while (pvclock_read_retry(src, version)); |
2697902b MT |
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 { | |
3aed64f6 | 82 | version = pvclock_read_begin(src); |
108b249c | 83 | ret = __pvclock_read_cycles(src, rdtsc_ordered()); |
3aed64f6 PB |
84 | flags = src->flags; |
85 | } while (pvclock_read_retry(src, version)); | |
7af192c9 | 86 | |
d63285e9 MT |
87 | if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) { |
88 | src->flags &= ~PVCLOCK_GUEST_STOPPED; | |
89 | pvclock_touch_watchdogs(); | |
90 | } | |
91 | ||
3a0d7256 | 92 | if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && |
42b5637d | 93 | (flags & PVCLOCK_TSC_STABLE_BIT)) |
3a0d7256 GC |
94 | return ret; |
95 | ||
489fb490 GC |
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 | ||
7af192c9 GH |
117 | return ret; |
118 | } | |
119 | ||
120 | void 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 | } |