| /* 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/memblock.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); |