167 lines
4.4 KiB
C
167 lines
4.4 KiB
C
/* paravirtual clock -- common code used by kvm/xen
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This program is free software; you can redistribute it and/or modify
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it under the terms of the GNU General Public License as published by
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the Free Software Foundation; either version 2 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU General Public License for more details.
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You should have received a copy of the GNU General Public License
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along with this program; if not, write to the Free Software
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Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#include <linux/kernel.h>
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#include <linux/percpu.h>
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#include <linux/notifier.h>
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#include <linux/sched.h>
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#include <linux/gfp.h>
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#include <linux/bootmem.h>
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#include <asm/fixmap.h>
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#include <asm/pvclock.h>
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static u8 valid_flags __read_mostly = 0;
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void pvclock_set_flags(u8 flags)
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{
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valid_flags = flags;
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}
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unsigned long pvclock_tsc_khz(struct pvclock_vcpu_time_info *src)
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{
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u64 pv_tsc_khz = 1000000ULL << 32;
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do_div(pv_tsc_khz, src->tsc_to_system_mul);
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if (src->tsc_shift < 0)
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pv_tsc_khz <<= -src->tsc_shift;
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else
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pv_tsc_khz >>= src->tsc_shift;
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return pv_tsc_khz;
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}
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void pvclock_touch_watchdogs(void)
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{
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touch_softlockup_watchdog_sync();
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clocksource_touch_watchdog();
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rcu_cpu_stall_reset();
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reset_hung_task_detector();
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}
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static atomic64_t last_value = ATOMIC64_INIT(0);
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void pvclock_resume(void)
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{
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atomic64_set(&last_value, 0);
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}
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u8 pvclock_read_flags(struct pvclock_vcpu_time_info *src)
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{
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unsigned version;
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cycle_t ret;
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u8 flags;
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do {
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version = __pvclock_read_cycles(src, &ret, &flags);
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} while ((src->version & 1) || version != src->version);
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return flags & valid_flags;
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}
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cycle_t pvclock_clocksource_read(struct pvclock_vcpu_time_info *src)
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{
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unsigned version;
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cycle_t ret;
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u64 last;
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u8 flags;
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do {
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version = __pvclock_read_cycles(src, &ret, &flags);
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} while ((src->version & 1) || version != src->version);
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if (unlikely((flags & PVCLOCK_GUEST_STOPPED) != 0)) {
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src->flags &= ~PVCLOCK_GUEST_STOPPED;
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pvclock_touch_watchdogs();
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}
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if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) &&
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(flags & PVCLOCK_TSC_STABLE_BIT))
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return ret;
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/*
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* Assumption here is that last_value, a global accumulator, always goes
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* forward. If we are less than that, we should not be much smaller.
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* We assume there is an error marging we're inside, and then the correction
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* does not sacrifice accuracy.
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*
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* For reads: global may have changed between test and return,
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* but this means someone else updated poked the clock at a later time.
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* We just need to make sure we are not seeing a backwards event.
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*
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* For updates: last_value = ret is not enough, since two vcpus could be
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* updating at the same time, and one of them could be slightly behind,
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* making the assumption that last_value always go forward fail to hold.
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*/
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last = atomic64_read(&last_value);
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do {
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if (ret < last)
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return last;
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last = atomic64_cmpxchg(&last_value, last, ret);
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} while (unlikely(last != ret));
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return ret;
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}
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void pvclock_read_wallclock(struct pvclock_wall_clock *wall_clock,
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struct pvclock_vcpu_time_info *vcpu_time,
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struct timespec *ts)
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{
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u32 version;
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u64 delta;
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struct timespec now;
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/* get wallclock at system boot */
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do {
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version = wall_clock->version;
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rmb(); /* fetch version before time */
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now.tv_sec = wall_clock->sec;
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now.tv_nsec = wall_clock->nsec;
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rmb(); /* fetch time before checking version */
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} while ((wall_clock->version & 1) || (version != wall_clock->version));
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delta = pvclock_clocksource_read(vcpu_time); /* time since system boot */
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delta += now.tv_sec * (u64)NSEC_PER_SEC + now.tv_nsec;
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now.tv_nsec = do_div(delta, NSEC_PER_SEC);
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now.tv_sec = delta;
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set_normalized_timespec(ts, now.tv_sec, now.tv_nsec);
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}
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#ifdef CONFIG_X86_64
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/*
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* Initialize the generic pvclock vsyscall state. This will allocate
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* a/some page(s) for the per-vcpu pvclock information, set up a
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* fixmap mapping for the page(s)
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*/
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int __init pvclock_init_vsyscall(struct pvclock_vsyscall_time_info *i,
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int size)
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{
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int idx;
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WARN_ON (size != PVCLOCK_VSYSCALL_NR_PAGES*PAGE_SIZE);
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for (idx = 0; idx <= (PVCLOCK_FIXMAP_END-PVCLOCK_FIXMAP_BEGIN); idx++) {
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__set_fixmap(PVCLOCK_FIXMAP_BEGIN + idx,
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__pa(i) + (idx*PAGE_SIZE),
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PAGE_KERNEL_VVAR);
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}
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return 0;
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}
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#endif
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