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> | |
20 | #include <asm/pvclock.h> | |
21 | ||
424c32f1 GC |
22 | static u8 valid_flags __read_mostly = 0; |
23 | ||
24 | void pvclock_set_flags(u8 flags) | |
25 | { | |
26 | valid_flags = flags; | |
27 | } | |
28 | ||
3807f345 GC |
29 | unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src) |
30 | { | |
a0854600 | 31 | u64 pv_tsc_khz = 1000000ULL << 32; |
3807f345 | 32 | |
a0854600 | 33 | do_div(pv_tsc_khz, src->tsc_to_system_mul); |
3807f345 | 34 | if (src->tsc_shift < 0) |
a0854600 | 35 | pv_tsc_khz <<= -src->tsc_shift; |
3807f345 | 36 | else |
a0854600 HH |
37 | pv_tsc_khz >>= src->tsc_shift; |
38 | return pv_tsc_khz; | |
3807f345 GC |
39 | } |
40 | ||
489fb490 GC |
41 | static atomic64_t last_value = ATOMIC64_INIT(0); |
42 | ||
e7a3481c JF |
43 | void pvclock_resume(void) |
44 | { | |
45 | atomic64_set(&last_value, 0); | |
46 | } | |
47 | ||
7af192c9 GH |
48 | cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) |
49 | { | |
7af192c9 | 50 | unsigned version; |
dce2db0a | 51 | cycle_t ret; |
489fb490 | 52 | u64 last; |
42b5637d | 53 | u8 flags; |
7af192c9 GH |
54 | |
55 | do { | |
dce2db0a | 56 | version = __pvclock_read_cycles(src, &ret, &flags); |
42b5637d | 57 | } while ((src->version & 1) || version != src->version); |
7af192c9 | 58 | |
3a0d7256 | 59 | if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && |
42b5637d | 60 | (flags & PVCLOCK_TSC_STABLE_BIT)) |
3a0d7256 GC |
61 | return ret; |
62 | ||
489fb490 GC |
63 | /* |
64 | * Assumption here is that last_value, a global accumulator, always goes | |
65 | * forward. If we are less than that, we should not be much smaller. | |
66 | * We assume there is an error marging we're inside, and then the correction | |
67 | * does not sacrifice accuracy. | |
68 | * | |
69 | * For reads: global may have changed between test and return, | |
70 | * but this means someone else updated poked the clock at a later time. | |
71 | * We just need to make sure we are not seeing a backwards event. | |
72 | * | |
73 | * For updates: last_value = ret is not enough, since two vcpus could be | |
74 | * updating at the same time, and one of them could be slightly behind, | |
75 | * making the assumption that last_value always go forward fail to hold. | |
76 | */ | |
77 | last = atomic64_read(&last_value); | |
78 | do { | |
79 | if (ret < last) | |
80 | return last; | |
81 | last = atomic64_cmpxchg(&last_value, last, ret); | |
82 | } while (unlikely(last != ret)); | |
83 | ||
7af192c9 GH |
84 | return ret; |
85 | } | |
86 | ||
87 | void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock, | |
88 | struct pvclock_vcpu_time_info *vcpu_time, | |
89 | struct timespec *ts) | |
90 | { | |
91 | u32 version; | |
92 | u64 delta; | |
93 | struct timespec now; | |
94 | ||
95 | /* get wallclock at system boot */ | |
96 | do { | |
97 | version = wall_clock->version; | |
98 | rmb(); /* fetch version before time */ | |
99 | now.tv_sec = wall_clock->sec; | |
100 | now.tv_nsec = wall_clock->nsec; | |
101 | rmb(); /* fetch time before checking version */ | |
102 | } while ((wall_clock->version & 1) || (version != wall_clock->version)); | |
103 | ||
104 | delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */ | |
105 | delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec; | |
106 | ||
107 | now.tv_nsec = do_div(delta, NSEC_PER_SEC); | |
108 | now.tv_sec = delta; | |
109 | ||
110 | set_normalized_timespec(ts, now.tv_sec, now.tv_nsec); | |
111 | } |