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 <linux/notifier.h>
21 #include <linux/sched.h>
22 #include <linux/gfp.h>
23 #include <linux/bootmem.h>
24 #include <linux/nmi.h>
25
26 #include <asm/fixmap.h>
27 #include <asm/pvclock.h>
28 #include <asm/vgtod.h>
29
30 static u8 valid_flags __read_mostly = 0;
31 static struct pvclock_vsyscall_time_info *pvti_cpu0_va __read_mostly;
32
pvclock_set_flags(u8 flags)33 void pvclock_set_flags(u8 flags)
34 {
35 valid_flags = flags;
36 }
37
pvclock_tsc_khz(struct pvclock_vcpu_time_info * src)38 unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
39 {
40 u64 pv_tsc_khz = 1000000ULL << 32;
41
42 do_div(pv_tsc_khz, src->tsc_to_system_mul);
43 if (src->tsc_shift < 0)
44 pv_tsc_khz <<= -src->tsc_shift;
45 else
46 pv_tsc_khz >>= src->tsc_shift;
47 return pv_tsc_khz;
48 }
49
pvclock_touch_watchdogs(void)50 void pvclock_touch_watchdogs(void)
51 {
52 touch_softlockup_watchdog_sync();
53 clocksource_touch_watchdog();
54 rcu_cpu_stall_reset();
55 reset_hung_task_detector();
56 }
57
58 static atomic64_t last_value = ATOMIC64_INIT(0);
59
pvclock_resume(void)60 void pvclock_resume(void)
61 {
62 atomic64_set(&last_value, 0);
63 }
64
pvclock_read_flags(struct pvclock_vcpu_time_info * src)65 u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
66 {
67 unsigned version;
68 u8 flags;
69
70 do {
71 version = pvclock_read_begin(src);
72 flags = src->flags;
73 } while (pvclock_read_retry(src, version));
74
75 return flags & valid_flags;
76 }
77
pvclock_clocksource_read(struct pvclock_vcpu_time_info * src)78 u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
79 {
80 unsigned version;
81 u64 ret;
82 u64 last;
83 u8 flags;
84
85 do {
86 version = pvclock_read_begin(src);
87 ret = __pvclock_read_cycles(src, rdtsc_ordered());
88 flags = src->flags;
89 } while (pvclock_read_retry(src, version));
90
91 if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
92 src->flags &= ~PVCLOCK_GUEST_STOPPED;
93 pvclock_touch_watchdogs();
94 }
95
96 if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
97 (flags & PVCLOCK_TSC_STABLE_BIT))
98 return ret;
99
100 /*
101 * Assumption here is that last_value, a global accumulator, always goes
102 * forward. If we are less than that, we should not be much smaller.
103 * We assume there is an error marging we're inside, and then the correction
104 * does not sacrifice accuracy.
105 *
106 * For reads: global may have changed between test and return,
107 * but this means someone else updated poked the clock at a later time.
108 * We just need to make sure we are not seeing a backwards event.
109 *
110 * For updates: last_value = ret is not enough, since two vcpus could be
111 * updating at the same time, and one of them could be slightly behind,
112 * making the assumption that last_value always go forward fail to hold.
113 */
114 last = atomic64_read(&last_value);
115 do {
116 if (ret < last)
117 return last;
118 last = atomic64_cmpxchg(&last_value, last, ret);
119 } while (unlikely(last != ret));
120
121 return ret;
122 }
123
pvclock_read_wallclock(struct pvclock_wall_clock * wall_clock,struct pvclock_vcpu_time_info * vcpu_time,struct timespec64 * ts)124 void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
125 struct pvclock_vcpu_time_info *vcpu_time,
126 struct timespec64 *ts)
127 {
128 u32 version;
129 u64 delta;
130 struct timespec64 now;
131
132 /* get wallclock at system boot */
133 do {
134 version = wall_clock->version;
135 rmb(); /* fetch version before time */
136 /*
137 * Note: wall_clock->sec is a u32 value, so it can
138 * only store dates between 1970 and 2106. To allow
139 * times beyond that, we need to create a new hypercall
140 * interface with an extended pvclock_wall_clock structure
141 * like ARM has.
142 */
143 now.tv_sec = wall_clock->sec;
144 now.tv_nsec = wall_clock->nsec;
145 rmb(); /* fetch time before checking version */
146 } while ((wall_clock->version & 1) || (version != wall_clock->version));
147
148 delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */
149 delta += now.tv_sec * NSEC_PER_SEC + now.tv_nsec;
150
151 now.tv_nsec = do_div(delta, NSEC_PER_SEC);
152 now.tv_sec = delta;
153
154 set_normalized_timespec64(ts, now.tv_sec, now.tv_nsec);
155 }
156
pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info * pvti)157 void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti)
158 {
159 WARN_ON(vclock_was_used(VCLOCK_PVCLOCK));
160 pvti_cpu0_va = pvti;
161 }
162
pvclock_get_pvti_cpu0_va(void)163 struct pvclock_vsyscall_time_info *pvclock_get_pvti_cpu0_va(void)
164 {
165 return pvti_cpu0_va;
166 }
167 EXPORT_SYMBOL_GPL(pvclock_get_pvti_cpu0_va);
168
