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Commit | Line | Data |
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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> | |
38b8d208 IM |
24 | #include <linux/nmi.h> |
25 | ||
71056ae2 | 26 | #include <asm/fixmap.h> |
7af192c9 GH |
27 | #include <asm/pvclock.h> |
28 | ||
424c32f1 GC |
29 | static u8 valid_flags __read_mostly = 0; |
30 | ||
31 | void pvclock_set_flags(u8 flags) | |
32 | { | |
33 | valid_flags = flags; | |
34 | } | |
35 | ||
3807f345 GC |
36 | unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src) |
37 | { | |
a0854600 | 38 | u64 pv_tsc_khz = 1000000ULL << 32; |
3807f345 | 39 | |
a0854600 | 40 | do_div(pv_tsc_khz, src->tsc_to_system_mul); |
3807f345 | 41 | if (src->tsc_shift < 0) |
a0854600 | 42 | pv_tsc_khz <<= -src->tsc_shift; |
3807f345 | 43 | else |
a0854600 HH |
44 | pv_tsc_khz >>= src->tsc_shift; |
45 | return pv_tsc_khz; | |
3807f345 GC |
46 | } |
47 | ||
d63285e9 MT |
48 | void pvclock_touch_watchdogs(void) |
49 | { | |
50 | touch_softlockup_watchdog_sync(); | |
51 | clocksource_touch_watchdog(); | |
52 | rcu_cpu_stall_reset(); | |
8b414521 | 53 | reset_hung_task_detector(); |
d63285e9 MT |
54 | } |
55 | ||
489fb490 GC |
56 | static atomic64_t last_value = ATOMIC64_INIT(0); |
57 | ||
e7a3481c JF |
58 | void pvclock_resume(void) |
59 | { | |
60 | atomic64_set(&last_value, 0); | |
61 | } | |
62 | ||
2697902b MT |
63 | u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src) |
64 | { | |
65 | unsigned version; | |
2697902b MT |
66 | u8 flags; |
67 | ||
68 | do { | |
3aed64f6 | 69 | version = pvclock_read_begin(src); |
ed911b43 | 70 | flags = src->flags; |
3aed64f6 | 71 | } while (pvclock_read_retry(src, version)); |
2697902b MT |
72 | |
73 | return flags & valid_flags; | |
74 | } | |
75 | ||
a5a1d1c2 | 76 | u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) |
7af192c9 | 77 | { |
7af192c9 | 78 | unsigned version; |
a5a1d1c2 | 79 | u64 ret; |
489fb490 | 80 | u64 last; |
42b5637d | 81 | u8 flags; |
7af192c9 GH |
82 | |
83 | do { | |
3aed64f6 | 84 | version = pvclock_read_begin(src); |
108b249c | 85 | ret = __pvclock_read_cycles(src, rdtsc_ordered()); |
3aed64f6 PB |
86 | flags = src->flags; |
87 | } while (pvclock_read_retry(src, version)); | |
7af192c9 | 88 | |
d63285e9 MT |
89 | if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) { |
90 | src->flags &= ~PVCLOCK_GUEST_STOPPED; | |
91 | pvclock_touch_watchdogs(); | |
92 | } | |
93 | ||
3a0d7256 | 94 | if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && |
42b5637d | 95 | (flags & PVCLOCK_TSC_STABLE_BIT)) |
3a0d7256 GC |
96 | return ret; |
97 | ||
489fb490 GC |
98 | /* |
99 | * Assumption here is that last_value, a global accumulator, always goes | |
100 | * forward. If we are less than that, we should not be much smaller. | |
101 | * We assume there is an error marging we're inside, and then the correction | |
102 | * does not sacrifice accuracy. | |
103 | * | |
104 | * For reads: global may have changed between test and return, | |
105 | * but this means someone else updated poked the clock at a later time. | |
106 | * We just need to make sure we are not seeing a backwards event. | |
107 | * | |
108 | * For updates: last_value = ret is not enough, since two vcpus could be | |
109 | * updating at the same time, and one of them could be slightly behind, | |
110 | * making the assumption that last_value always go forward fail to hold. | |
111 | */ | |
112 | last = atomic64_read(&last_value); | |
113 | do { | |
114 | if (ret < last) | |
115 | return last; | |
116 | last = atomic64_cmpxchg(&last_value, last, ret); | |
117 | } while (unlikely(last != ret)); | |
118 | ||
7af192c9 GH |
119 | return ret; |
120 | } | |
121 | ||
122 | void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock, | |
123 | struct pvclock_vcpu_time_info *vcpu_time, | |
124 | struct timespec *ts) | |
125 | { | |
126 | u32 version; | |
127 | u64 delta; | |
128 | struct timespec now; | |
129 | ||
130 | /* get wallclock at system boot */ | |
131 | do { | |
132 | version = wall_clock->version; | |
133 | rmb(); /* fetch version before time */ | |
134 | now.tv_sec = wall_clock->sec; | |
135 | now.tv_nsec = wall_clock->nsec; | |
136 | rmb(); /* fetch time before checking version */ | |
137 | } while ((wall_clock->version & 1) || (version != wall_clock->version)); | |
138 | ||
139 | delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */ | |
140 | delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec; | |
141 | ||
142 | now.tv_nsec = do_div(delta, NSEC_PER_SEC); | |
143 | now.tv_sec = delta; | |
144 | ||
145 | set_normalized_timespec(ts, now.tv_sec, now.tv_nsec); | |
146 | } |