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1// SPDX-License-Identifier: GPL-2.0-or-later
2/* paravirtual clock -- common code used by kvm/xen
3
4*/
5
6#include <linux/clocksource.h>
7#include <linux/kernel.h>
8#include <linux/percpu.h>
9#include <linux/notifier.h>
10#include <linux/sched.h>
11#include <linux/gfp.h>
12#include <linux/memblock.h>
13#include <linux/nmi.h>
14
15#include <asm/fixmap.h>
16#include <asm/pvclock.h>
17#include <asm/vgtod.h>
18
19static u8 valid_flags __read_mostly = 0;
20static struct pvclock_vsyscall_time_info *pvti_cpu0_va __read_mostly;
21
22void pvclock_set_flags(u8 flags)
23{
24 valid_flags = flags;
25}
26
27unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
28{
29 u64 pv_tsc_khz = 1000000ULL << 32;
30
31 do_div(pv_tsc_khz, src->tsc_to_system_mul);
32 if (src->tsc_shift < 0)
33 pv_tsc_khz <<= -src->tsc_shift;
34 else
35 pv_tsc_khz >>= src->tsc_shift;
36 return pv_tsc_khz;
37}
38
39void pvclock_touch_watchdogs(void)
40{
41 touch_softlockup_watchdog_sync();
42 clocksource_touch_watchdog();
43 rcu_cpu_stall_reset();
44 reset_hung_task_detector();
45}
46
47static atomic64_t last_value = ATOMIC64_INIT(0);
48
49void pvclock_resume(void)
50{
51 atomic64_set(&last_value, 0);
52}
53
54u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
55{
56 unsigned version;
57 u8 flags;
58
59 do {
60 version = pvclock_read_begin(src);
61 flags = src->flags;
62 } while (pvclock_read_retry(src, version));
63
64 return flags & valid_flags;
65}
66
67u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
68{
69 unsigned version;
70 u64 ret;
71 u64 last;
72 u8 flags;
73
74 do {
75 version = pvclock_read_begin(src);
76 ret = __pvclock_read_cycles(src, rdtsc_ordered());
77 flags = src->flags;
78 } while (pvclock_read_retry(src, version));
79
80 if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
81 src->flags &= ~PVCLOCK_GUEST_STOPPED;
82 pvclock_touch_watchdogs();
83 }
84
85 if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
86 (flags & PVCLOCK_TSC_STABLE_BIT))
87 return ret;
88
89 /*
90 * Assumption here is that last_value, a global accumulator, always goes
91 * forward. If we are less than that, we should not be much smaller.
92 * We assume there is an error marging we're inside, and then the correction
93 * does not sacrifice accuracy.
94 *
95 * For reads: global may have changed between test and return,
96 * but this means someone else updated poked the clock at a later time.
97 * We just need to make sure we are not seeing a backwards event.
98 *
99 * For updates: last_value = ret is not enough, since two vcpus could be
100 * updating at the same time, and one of them could be slightly behind,
101 * making the assumption that last_value always go forward fail to hold.
102 */
103 last = atomic64_read(&last_value);
104 do {
105 if (ret < last)
106 return last;
107 last = atomic64_cmpxchg(&last_value, last, ret);
108 } while (unlikely(last != ret));
109
110 return ret;
111}
112
113void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
114 struct pvclock_vcpu_time_info *vcpu_time,
115 struct timespec64 *ts)
116{
117 u32 version;
118 u64 delta;
119 struct timespec64 now;
120
121 /* get wallclock at system boot */
122 do {
123 version = wall_clock->version;
124 rmb(); /* fetch version before time */
125 /*
126 * Note: wall_clock->sec is a u32 value, so it can
127 * only store dates between 1970 and 2106. To allow
128 * times beyond that, we need to create a new hypercall
129 * interface with an extended pvclock_wall_clock structure
130 * like ARM has.
131 */
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 * 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_timespec64(ts, now.tv_sec, now.tv_nsec);
144}
145
146void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti)
147{
148 WARN_ON(vclock_was_used(VCLOCK_PVCLOCK));
149 pvti_cpu0_va = pvti;
150}
151
152struct pvclock_vsyscall_time_info *pvclock_get_pvti_cpu0_va(void)
153{
154 return pvti_cpu0_va;
155}
156EXPORT_SYMBOL_GPL(pvclock_get_pvti_cpu0_va);
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 <asm/fixmap.h>
25#include <asm/pvclock.h>
26
27static u8 valid_flags __read_mostly = 0;
28
29void pvclock_set_flags(u8 flags)
30{
31 valid_flags = flags;
32}
33
34unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
35{
36 u64 pv_tsc_khz = 1000000ULL << 32;
37
38 do_div(pv_tsc_khz, src->tsc_to_system_mul);
39 if (src->tsc_shift < 0)
40 pv_tsc_khz <<= -src->tsc_shift;
41 else
42 pv_tsc_khz >>= src->tsc_shift;
43 return pv_tsc_khz;
44}
45
46void pvclock_touch_watchdogs(void)
47{
48 touch_softlockup_watchdog_sync();
49 clocksource_touch_watchdog();
50 rcu_cpu_stall_reset();
51 reset_hung_task_detector();
52}
53
54static atomic64_t last_value = ATOMIC64_INIT(0);
55
56void pvclock_resume(void)
57{
58 atomic64_set(&last_value, 0);
59}
60
61u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
62{
63 unsigned version;
64 cycle_t ret;
65 u8 flags;
66
67 do {
68 version = __pvclock_read_cycles(src, &ret, &flags);
69 } while ((src->version & 1) || version != src->version);
70
71 return flags & valid_flags;
72}
73
74cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
75{
76 unsigned version;
77 cycle_t ret;
78 u64 last;
79 u8 flags;
80
81 do {
82 version = __pvclock_read_cycles(src, &ret, &flags);
83 } while ((src->version & 1) || version != src->version);
84
85 if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
86 src->flags &= ~PVCLOCK_GUEST_STOPPED;
87 pvclock_touch_watchdogs();
88 }
89
90 if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
91 (flags & PVCLOCK_TSC_STABLE_BIT))
92 return ret;
93
94 /*
95 * Assumption here is that last_value, a global accumulator, always goes
96 * forward. If we are less than that, we should not be much smaller.
97 * We assume there is an error marging we're inside, and then the correction
98 * does not sacrifice accuracy.
99 *
100 * For reads: global may have changed between test and return,
101 * but this means someone else updated poked the clock at a later time.
102 * We just need to make sure we are not seeing a backwards event.
103 *
104 * For updates: last_value = ret is not enough, since two vcpus could be
105 * updating at the same time, and one of them could be slightly behind,
106 * making the assumption that last_value always go forward fail to hold.
107 */
108 last = atomic64_read(&last_value);
109 do {
110 if (ret < last)
111 return last;
112 last = atomic64_cmpxchg(&last_value, last, ret);
113 } while (unlikely(last != ret));
114
115 return ret;
116}
117
118void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
119 struct pvclock_vcpu_time_info *vcpu_time,
120 struct timespec *ts)
121{
122 u32 version;
123 u64 delta;
124 struct timespec now;
125
126 /* get wallclock at system boot */
127 do {
128 version = wall_clock->version;
129 rmb(); /* fetch version before time */
130 now.tv_sec = wall_clock->sec;
131 now.tv_nsec = wall_clock->nsec;
132 rmb(); /* fetch time before checking version */
133 } while ((wall_clock->version & 1) || (version != wall_clock->version));
134
135 delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */
136 delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
137
138 now.tv_nsec = do_div(delta, NSEC_PER_SEC);
139 now.tv_sec = delta;
140
141 set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
142}
143
144#ifdef CONFIG_X86_64
145/*
146 * Initialize the generic pvclock vsyscall state. This will allocate
147 * a/some page(s) for the per-vcpu pvclock information, set up a
148 * fixmap mapping for the page(s)
149 */
150
151int __init pvclock_init_vsyscall(struct pvclock_vsyscall_time_info *i,
152 int size)
153{
154 int idx;
155
156 WARN_ON (size != PVCLOCK_VSYSCALL_NR_PAGES*PAGE_SIZE);
157
158 for (idx = 0; idx <= (PVCLOCK_FIXMAP_END-PVCLOCK_FIXMAP_BEGIN); idx++) {
159 __set_fixmap(PVCLOCK_FIXMAP_BEGIN + idx,
160 __pa(i) + (idx*PAGE_SIZE),
161 PAGE_KERNEL_VVAR);
162 }
163
164 return 0;
165}
166#endif