diff options
Diffstat (limited to '')
| -rw-r--r-- | arch/x86/kernel/pvclock.c | 167 |
1 files changed, 167 insertions, 0 deletions
diff --git a/arch/x86/kernel/pvclock.c b/arch/x86/kernel/pvclock.c new file mode 100644 index 000000000..637982efe --- /dev/null +++ b/arch/x86/kernel/pvclock.c @@ -0,0 +1,167 @@ +/* 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 + MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + 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> +#include <asm/vgtod.h> + +static u8 valid_flags __read_mostly = 0; +static struct pvclock_vsyscall_time_info *pvti_cpu0_va __read_mostly; + +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; + else + pv_tsc_khz >>= src->tsc_shift; + return pv_tsc_khz; +} + +void pvclock_touch_watchdogs(void) +{ + touch_softlockup_watchdog_sync(); + clocksource_touch_watchdog(); + rcu_cpu_stall_reset(); + reset_hung_task_detector(); +} + +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)) { + src->flags &= ~PVCLOCK_GUEST_STOPPED; + pvclock_touch_watchdogs(); + } + + if ((valid_flags & PVCLOCK_TSC_STABLE_BIT) && + (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 timespec64 *ts) +{ + u32 version; + u64 delta; + struct timespec64 now; + + /* get wallclock at system boot */ + do { + version = wall_clock->version; + rmb(); /* fetch version before time */ + /* + * Note: wall_clock->sec is a u32 value, so it can + * only store dates between 1970 and 2106. To allow + * times beyond that, we need to create a new hypercall + * interface with an extended pvclock_wall_clock structure + * like ARM has. + */ + 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 * NSEC_PER_SEC + now.tv_nsec; + + now.tv_nsec = do_div(delta, NSEC_PER_SEC); + now.tv_sec = delta; + + set_normalized_timespec64(ts, now.tv_sec, now.tv_nsec); +} + +void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti) +{ + WARN_ON(vclock_was_used(VCLOCK_PVCLOCK)); + pvti_cpu0_va = pvti; +} + +struct pvclock_vsyscall_time_info *pvclock_get_pvti_cpu0_va(void) +{ + return pvti_cpu0_va; +} +EXPORT_SYMBOL_GPL(pvclock_get_pvti_cpu0_va); |