blob: 5c3f6d6a5078338e0a0806026e9465f057c92285 [file] [log] [blame]
/* paravirtual clock -- common code used by kvm/xen
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
#include <linux/kernel.h>
#include <linux/percpu.h>
#include <linux/notifier.h>
#include <linux/sched.h>
#include <linux/gfp.h>
#include <linux/bootmem.h>
#include <linux/nmi.h>
#include <asm/fixmap.h>
#include <asm/pvclock.h>
static u8 valid_flags __read_mostly = 0;
void pvclock_set_flags(u8 flags)
valid_flags = flags;
unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
u64 pv_tsc_khz = 1000000ULL << 32;
do_div(pv_tsc_khz, src->tsc_to_system_mul);
if (src->tsc_shift < 0)
pv_tsc_khz <<= -src->tsc_shift;
pv_tsc_khz >>= src->tsc_shift;
return pv_tsc_khz;
void pvclock_touch_watchdogs(void)
static atomic64_t last_value = ATOMIC64_INIT(0);
void pvclock_resume(void)
atomic64_set(&last_value, 0);
u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
unsigned version;
u8 flags;
do {
version = pvclock_read_begin(src);
flags = src->flags;
} while (pvclock_read_retry(src, version));
return flags & valid_flags;
u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
unsigned version;
u64 ret;
u64 last;
u8 flags;
do {
version = pvclock_read_begin(src);
ret = __pvclock_read_cycles(src, rdtsc_ordered());
flags = src->flags;
} while (pvclock_read_retry(src, version));
if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
return ret;
* Assumption here is that last_value, a global accumulator, always goes
* forward. If we are less than that, we should not be much smaller.
* We assume there is an error marging we're inside, and then the correction
* does not sacrifice accuracy.
* For reads: global may have changed between test and return,
* but this means someone else updated poked the clock at a later time.
* We just need to make sure we are not seeing a backwards event.
* For updates: last_value = ret is not enough, since two vcpus could be
* updating at the same time, and one of them could be slightly behind,
* making the assumption that last_value always go forward fail to hold.
last = atomic64_read(&last_value);
do {
if (ret < last)
return last;
last = atomic64_cmpxchg(&last_value, last, ret);
} while (unlikely(last != ret));
return ret;
void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
struct pvclock_vcpu_time_info *vcpu_time,
struct timespec *ts)
u32 version;
u64 delta;
struct timespec now;
/* get wallclock at system boot */
do {
version = wall_clock->version;
rmb(); /* fetch version before time */
now.tv_sec = wall_clock->sec;
now.tv_nsec = wall_clock->nsec;
rmb(); /* fetch time before checking version */
} while ((wall_clock->version & 1) || (version != wall_clock->version));
delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */
delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
now.tv_nsec = do_div(delta, NSEC_PER_SEC);
now.tv_sec = delta;
set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);