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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> | |
20 | #include <asm/pvclock.h> | |
21 | ||
22 | /* | |
23 | * These are perodically updated | |
24 | * xen: magic shared_info page | |
25 | * kvm: gpa registered via msr | |
26 | * and then copied here. | |
27 | */ | |
28 | struct pvclock_shadow_time { | |
29 | u64 tsc_timestamp; /* TSC at last update of time vals. */ | |
30 | u64 system_timestamp; /* Time, in nanosecs, since boot. */ | |
31 | u32 tsc_to_nsec_mul; | |
32 | int tsc_shift; | |
33 | u32 version; | |
34 | }; | |
35 | ||
36 | /* | |
37 | * Scale a 64-bit delta by scaling and multiplying by a 32-bit fraction, | |
38 | * yielding a 64-bit result. | |
39 | */ | |
40 | static inline u64 scale_delta(u64 delta, u32 mul_frac, int shift) | |
41 | { | |
42 | u64 product; | |
43 | #ifdef __i386__ | |
44 | u32 tmp1, tmp2; | |
45 | #endif | |
46 | ||
47 | if (shift < 0) | |
48 | delta >>= -shift; | |
49 | else | |
50 | delta <<= shift; | |
51 | ||
52 | #ifdef __i386__ | |
53 | __asm__ ( | |
54 | "mul %5 ; " | |
55 | "mov %4,%%eax ; " | |
56 | "mov %%edx,%4 ; " | |
57 | "mul %5 ; " | |
58 | "xor %5,%5 ; " | |
59 | "add %4,%%eax ; " | |
60 | "adc %5,%%edx ; " | |
61 | : "=A" (product), "=r" (tmp1), "=r" (tmp2) | |
62 | : "a" ((u32)delta), "1" ((u32)(delta >> 32)), "2" (mul_frac) ); | |
2ad76643 | 63 | #elif defined(__x86_64__) |
7af192c9 GH |
64 | __asm__ ( |
65 | "mul %%rdx ; shrd $32,%%rdx,%%rax" | |
66 | : "=a" (product) : "0" (delta), "d" ((u64)mul_frac) ); | |
67 | #else | |
68 | #error implement me! | |
69 | #endif | |
70 | ||
71 | return product; | |
72 | } | |
73 | ||
74 | static u64 pvclock_get_nsec_offset(struct pvclock_shadow_time *shadow) | |
75 | { | |
76 | u64 delta = native_read_tsc() - shadow->tsc_timestamp; | |
77 | return scale_delta(delta, shadow->tsc_to_nsec_mul, shadow->tsc_shift); | |
78 | } | |
79 | ||
80 | /* | |
81 | * Reads a consistent set of time-base values from hypervisor, | |
82 | * into a shadow data area. | |
83 | */ | |
84 | static unsigned pvclock_get_time_values(struct pvclock_shadow_time *dst, | |
85 | struct pvclock_vcpu_time_info *src) | |
86 | { | |
87 | do { | |
88 | dst->version = src->version; | |
89 | rmb(); /* fetch version before data */ | |
90 | dst->tsc_timestamp = src->tsc_timestamp; | |
91 | dst->system_timestamp = src->system_time; | |
92 | dst->tsc_to_nsec_mul = src->tsc_to_system_mul; | |
93 | dst->tsc_shift = src->tsc_shift; | |
94 | rmb(); /* test version after fetching data */ | |
95 | } while ((src->version & 1) || (dst->version != src->version)); | |
96 | ||
97 | return dst->version; | |
98 | } | |
99 | ||
3807f345 GC |
100 | unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src) |
101 | { | |
a0854600 | 102 | u64 pv_tsc_khz = 1000000ULL << 32; |
3807f345 | 103 | |
a0854600 | 104 | do_div(pv_tsc_khz, src->tsc_to_system_mul); |
3807f345 | 105 | if (src->tsc_shift < 0) |
a0854600 | 106 | pv_tsc_khz <<= -src->tsc_shift; |
3807f345 | 107 | else |
a0854600 HH |
108 | pv_tsc_khz >>= src->tsc_shift; |
109 | return pv_tsc_khz; | |
3807f345 GC |
110 | } |
111 | ||
7af192c9 GH |
112 | cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) |
113 | { | |
114 | struct pvclock_shadow_time shadow; | |
115 | unsigned version; | |
116 | cycle_t ret, offset; | |
117 | ||
118 | do { | |
119 | version = pvclock_get_time_values(&shadow, src); | |
120 | barrier(); | |
121 | offset = pvclock_get_nsec_offset(&shadow); | |
122 | ret = shadow.system_timestamp + offset; | |
123 | barrier(); | |
124 | } while (version != src->version); | |
125 | ||
126 | return ret; | |
127 | } | |
128 | ||
129 | void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock, | |
130 | struct pvclock_vcpu_time_info *vcpu_time, | |
131 | struct timespec *ts) | |
132 | { | |
133 | u32 version; | |
134 | u64 delta; | |
135 | struct timespec now; | |
136 | ||
137 | /* get wallclock at system boot */ | |
138 | do { | |
139 | version = wall_clock->version; | |
140 | rmb(); /* fetch version before time */ | |
141 | now.tv_sec = wall_clock->sec; | |
142 | now.tv_nsec = wall_clock->nsec; | |
143 | rmb(); /* fetch time before checking version */ | |
144 | } while ((wall_clock->version & 1) || (version != wall_clock->version)); | |
145 | ||
146 | delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */ | |
147 | delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec; | |
148 | ||
149 | now.tv_nsec = do_div(delta, NSEC_PER_SEC); | |
150 | now.tv_sec = delta; | |
151 | ||
152 | set_normalized_timespec(ts, now.tv_sec, now.tv_nsec); | |
153 | } |