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matosattibonzini
matosatti
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PTP: add kvm PTP driver
Add a driver with gettime method returning hosts realtime clock. This allows Chrony to synchronize host and guest clocks with high precision (see results below). chronyc> sources MS Name/IP address Stratum Poll Reach LastRx Last sample =============================================================================== To configure Chronyd to use PHC refclock, add the following line to its configuration file: refclock PHC /dev/ptpX poll 3 dpoll -2 offset 0 Where /dev/ptpX is the kvmclock PTP clock. Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com> Acked-by: Richard Cochran <richardcochran@gmail.com> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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‎drivers/ptp/Kconfig

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@@ -90,4 +90,16 @@ config PTP_1588_CLOCK_PCH
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To compile this driver as a module, choose M here: the module
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will be called ptp_pch.
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config PTP_1588_CLOCK_KVM
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tristate "KVM virtual PTP clock"
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depends on PTP_1588_CLOCK
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depends on KVM_GUEST && X86
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default y
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help
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This driver adds support for using kvm infrastructure as a PTP
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clock. This clock is only useful if you are using KVM guests.
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To compile this driver as a module, choose M here: the module
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will be called ptp_kvm.
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endmenu

‎drivers/ptp/Makefile

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@@ -6,3 +6,4 @@ ptp-y := ptp_clock.o ptp_chardev.o ptp_sysfs.o
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obj-$(CONFIG_PTP_1588_CLOCK) += ptp.o
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obj-$(CONFIG_PTP_1588_CLOCK_IXP46X) += ptp_ixp46x.o
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obj-$(CONFIG_PTP_1588_CLOCK_PCH) += ptp_pch.o
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obj-$(CONFIG_PTP_1588_CLOCK_KVM) += ptp_kvm.o

‎drivers/ptp/ptp_kvm.c

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@@ -0,0 +1,200 @@
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/*
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* Virtual PTP 1588 clock for use with KVM guests
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*
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* Copyright (C) 2017 Red Hat Inc.
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*
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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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*
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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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*
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*/
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#include <linux/device.h>
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#include <linux/err.h>
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#include <linux/init.h>
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#include <linux/kernel.h>
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#include <linux/module.h>
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#include <uapi/linux/kvm_para.h>
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#include <asm/kvm_para.h>
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#include <asm/pvclock.h>
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#include <asm/kvmclock.h>
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#include <uapi/asm/kvm_para.h>
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#include <linux/ptp_clock_kernel.h>
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struct kvm_ptp_clock {
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struct ptp_clock *ptp_clock;
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struct ptp_clock_info caps;
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};
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DEFINE_SPINLOCK(kvm_ptp_lock);
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static struct pvclock_vsyscall_time_info *hv_clock;
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static struct kvm_clock_pairing clock_pair;
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static phys_addr_t clock_pair_gpa;
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static int ptp_kvm_get_time_fn(ktime_t *device_time,
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struct system_counterval_t *system_counter,
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void *ctx)
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{
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unsigned long ret;
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struct timespec64 tspec;
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unsigned version;
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int cpu;
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struct pvclock_vcpu_time_info *src;
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spin_lock(&kvm_ptp_lock);
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preempt_disable_notrace();
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cpu = smp_processor_id();
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src = &hv_clock[cpu].pvti;
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do {
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/*
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* We are using a TSC value read in the hosts
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* kvm_hc_clock_pairing handling.
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* So any changes to tsc_to_system_mul
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* and tsc_shift or any other pvclock
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* data invalidate that measurement.
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*/
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version = pvclock_read_begin(src);
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ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
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clock_pair_gpa,
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KVM_CLOCK_PAIRING_WALLCLOCK);
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if (ret != 0) {
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pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
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spin_unlock(&kvm_ptp_lock);
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preempt_enable_notrace();
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return -EOPNOTSUPP;
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}
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tspec.tv_sec = clock_pair.sec;
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tspec.tv_nsec = clock_pair.nsec;
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ret = __pvclock_read_cycles(src, clock_pair.tsc);
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} while (pvclock_read_retry(src, version));
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preempt_enable_notrace();
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system_counter->cycles = ret;
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system_counter->cs = &kvm_clock;
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*device_time = timespec64_to_ktime(tspec);
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spin_unlock(&kvm_ptp_lock);
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return 0;
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}
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static int ptp_kvm_getcrosststamp(struct ptp_clock_info *ptp,
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struct system_device_crosststamp *xtstamp)
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{
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return get_device_system_crosststamp(ptp_kvm_get_time_fn, NULL,
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NULL, xtstamp);
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}
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/*
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* PTP clock operations
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*/
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static int ptp_kvm_adjfreq(struct ptp_clock_info *ptp, s32 ppb)
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{
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return -EOPNOTSUPP;
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}
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static int ptp_kvm_adjtime(struct ptp_clock_info *ptp, s64 delta)
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{
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return -EOPNOTSUPP;
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}
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static int ptp_kvm_settime(struct ptp_clock_info *ptp,
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const struct timespec64 *ts)
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{
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return -EOPNOTSUPP;
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}
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static int ptp_kvm_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
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{
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unsigned long ret;
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struct timespec64 tspec;
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spin_lock(&kvm_ptp_lock);
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ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
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clock_pair_gpa,
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KVM_CLOCK_PAIRING_WALLCLOCK);
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if (ret != 0) {
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pr_err_ratelimited("clock offset hypercall ret %lu\n", ret);
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spin_unlock(&kvm_ptp_lock);
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return -EOPNOTSUPP;
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}
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tspec.tv_sec = clock_pair.sec;
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tspec.tv_nsec = clock_pair.nsec;
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spin_unlock(&kvm_ptp_lock);
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memcpy(ts, &tspec, sizeof(struct timespec64));
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return 0;
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}
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static int ptp_kvm_enable(struct ptp_clock_info *ptp,
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struct ptp_clock_request *rq, int on)
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{
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return -EOPNOTSUPP;
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}
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static struct ptp_clock_info ptp_kvm_caps = {
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.owner = THIS_MODULE,
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.name = "KVM virtual PTP",
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.max_adj = 0,
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.n_ext_ts = 0,
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.n_pins = 0,
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.pps = 0,
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.adjfreq = ptp_kvm_adjfreq,
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.adjtime = ptp_kvm_adjtime,
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.gettime64 = ptp_kvm_gettime,
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.settime64 = ptp_kvm_settime,
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.enable = ptp_kvm_enable,
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.getcrosststamp = ptp_kvm_getcrosststamp,
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};
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/* module operations */
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static struct kvm_ptp_clock kvm_ptp_clock;
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static void __exit ptp_kvm_exit(void)
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{
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ptp_clock_unregister(kvm_ptp_clock.ptp_clock);
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}
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static int __init ptp_kvm_init(void)
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{
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clock_pair_gpa = slow_virt_to_phys(&clock_pair);
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hv_clock = pvclock_pvti_cpu0_va();
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if (!hv_clock)
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return -ENODEV;
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kvm_ptp_clock.caps = ptp_kvm_caps;
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kvm_ptp_clock.ptp_clock = ptp_clock_register(&kvm_ptp_clock.caps, NULL);
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if (IS_ERR(kvm_ptp_clock.ptp_clock))
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return PTR_ERR(kvm_ptp_clock.ptp_clock);
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return 0;
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}
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module_init(ptp_kvm_init);
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module_exit(ptp_kvm_exit);
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MODULE_AUTHOR("Marcelo Tosatti <mtosatti@redhat.com>");
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MODULE_DESCRIPTION("PTP clock using KVMCLOCK");
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MODULE_LICENSE("GPL");

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