1 /* paravirtual clock -- common code used by kvm/xen
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.
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.
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
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>
27 static u8 valid_flags __read_mostly
= 0;
29 void pvclock_set_flags(u8 flags
)
34 unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info
*src
)
36 u64 pv_tsc_khz
= 1000000ULL << 32;
38 do_div(pv_tsc_khz
, src
->tsc_to_system_mul
);
39 if (src
->tsc_shift
< 0)
40 pv_tsc_khz
<<= -src
->tsc_shift
;
42 pv_tsc_khz
>>= src
->tsc_shift
;
46 void pvclock_touch_watchdogs(void)
48 touch_softlockup_watchdog_sync();
49 clocksource_touch_watchdog();
50 rcu_cpu_stall_reset();
53 static atomic64_t last_value
= ATOMIC64_INIT(0);
55 void pvclock_resume(void)
57 atomic64_set(&last_value
, 0);
60 u8
pvclock_read_flags(struct pvclock_vcpu_time_info
*src
)
67 version
= __pvclock_read_cycles(src
, &ret
, &flags
);
68 } while ((src
->version
& 1) || version
!= src
->version
);
70 return flags
& valid_flags
;
73 cycle_t
pvclock_clocksource_read(struct pvclock_vcpu_time_info
*src
)
81 version
= __pvclock_read_cycles(src
, &ret
, &flags
);
82 } while ((src
->version
& 1) || version
!= src
->version
);
84 if (unlikely((flags
& PVCLOCK_GUEST_STOPPED
) != 0)) {
85 src
->flags
&= ~PVCLOCK_GUEST_STOPPED
;
86 pvclock_touch_watchdogs();
89 if ((valid_flags
& PVCLOCK_TSC_STABLE_BIT
) &&
90 (flags
& PVCLOCK_TSC_STABLE_BIT
))
94 * Assumption here is that last_value, a global accumulator, always goes
95 * forward. If we are less than that, we should not be much smaller.
96 * We assume there is an error marging we're inside, and then the correction
97 * does not sacrifice accuracy.
99 * For reads: global may have changed between test and return,
100 * but this means someone else updated poked the clock at a later time.
101 * We just need to make sure we are not seeing a backwards event.
103 * For updates: last_value = ret is not enough, since two vcpus could be
104 * updating at the same time, and one of them could be slightly behind,
105 * making the assumption that last_value always go forward fail to hold.
107 last
= atomic64_read(&last_value
);
111 last
= atomic64_cmpxchg(&last_value
, last
, ret
);
112 } while (unlikely(last
!= ret
));
117 void pvclock_read_wallclock(struct pvclock_wall_clock
*wall_clock
,
118 struct pvclock_vcpu_time_info
*vcpu_time
,
125 /* get wallclock at system boot */
127 version
= wall_clock
->version
;
128 rmb(); /* fetch version before time */
129 now
.tv_sec
= wall_clock
->sec
;
130 now
.tv_nsec
= wall_clock
->nsec
;
131 rmb(); /* fetch time before checking version */
132 } while ((wall_clock
->version
& 1) || (version
!= wall_clock
->version
));
134 delta
= pvclock_clocksource_read(vcpu_time
); /* time since system boot */
135 delta
+= now
.tv_sec
* (u64
)NSEC_PER_SEC
+ now
.tv_nsec
;
137 now
.tv_nsec
= do_div(delta
, NSEC_PER_SEC
);
140 set_normalized_timespec(ts
, now
.tv_sec
, now
.tv_nsec
);
145 * Initialize the generic pvclock vsyscall state. This will allocate
146 * a/some page(s) for the per-vcpu pvclock information, set up a
147 * fixmap mapping for the page(s)
150 int __init
pvclock_init_vsyscall(struct pvclock_vsyscall_time_info
*i
,
155 WARN_ON (size
!= PVCLOCK_VSYSCALL_NR_PAGES
*PAGE_SIZE
);
157 for (idx
= 0; idx
<= (PVCLOCK_FIXMAP_END
-PVCLOCK_FIXMAP_BEGIN
); idx
++) {
158 __set_fixmap(PVCLOCK_FIXMAP_BEGIN
+ idx
,
159 __pa(i
) + (idx
*PAGE_SIZE
),