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156 lines
3.9 KiB
156 lines
3.9 KiB
// SPDX-License-Identifier: GPL-2.0-or-later |
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/* paravirtual clock -- common code used by kvm/xen |
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*/ |
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#include <linux/clocksource.h> |
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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/memblock.h> |
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#include <linux/nmi.h> |
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#include <asm/fixmap.h> |
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#include <asm/pvclock.h> |
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#include <asm/vgtod.h> |
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static u8 valid_flags __read_mostly = 0; |
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static struct pvclock_vsyscall_time_info *pvti_cpu0_va __read_mostly; |
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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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u8 flags; |
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do { |
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version = pvclock_read_begin(src); |
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flags = src->flags; |
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} while (pvclock_read_retry(src, version)); |
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return flags & valid_flags; |
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} |
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u64 pvclock_clocksource_read(struct pvclock_vcpu_time_info *src) |
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{ |
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unsigned version; |
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u64 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_begin(src); |
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ret = __pvclock_read_cycles(src, rdtsc_ordered()); |
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flags = src->flags; |
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} while (pvclock_read_retry(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 timespec64 *ts) |
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{ |
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u32 version; |
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u64 delta; |
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struct timespec64 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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/* |
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* Note: wall_clock->sec is a u32 value, so it can |
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* only store dates between 1970 and 2106. To allow |
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* times beyond that, we need to create a new hypercall |
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* interface with an extended pvclock_wall_clock structure |
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* like ARM has. |
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*/ |
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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 * 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_timespec64(ts, now.tv_sec, now.tv_nsec); |
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} |
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void pvclock_set_pvti_cpu0_va(struct pvclock_vsyscall_time_info *pvti) |
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{ |
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WARN_ON(vclock_was_used(VDSO_CLOCKMODE_PVCLOCK)); |
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pvti_cpu0_va = pvti; |
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} |
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struct pvclock_vsyscall_time_info *pvclock_get_pvti_cpu0_va(void) |
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{ |
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return pvti_cpu0_va; |
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} |
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EXPORT_SYMBOL_GPL(pvclock_get_pvti_cpu0_va);
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