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 =============================================================================== #* PHC0 0 3 377 4 +162ns[ -683ns] +/- 11ns 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 --- drivers/ptp/Kconfig | 12 ++ drivers/ptp/Makefile | 1 drivers/ptp/ptp_kvm.c | 202 ++++++++++++++++++++++++++++++++++++++++++++++++++ 3 files changed, 215 insertions(+) v2: check for kvmclock (Radim) initialize global variables before device registration (Radim) v3: use cross timestamps callback (Paolo, Miroslav, Radim) v4: remove gettime64 callback (Paolo) v5: drop useless nsec assignment (Radim) Index: kvm-ptpdriver/drivers/ptp/Kconfig =================================================================== --- kvm-ptpdriver.orig/drivers/ptp/Kconfig 2017-01-24 09:03:47.604586098 -0200 +++ kvm-ptpdriver/drivers/ptp/Kconfig 2017-01-24 09:05:06.321704124 -0200 @@ -90,4 +90,16 @@ To compile this driver as a module, choose M here: the module will be called ptp_pch. +config PTP_1588_CLOCK_KVM + tristate "KVM virtual PTP clock" + depends on PTP_1588_CLOCK + depends on KVM_GUEST + default y + help + This driver adds support for using kvm infrastructure as a PTP + clock. This clock is only useful if you are using KVM guests. + + To compile this driver as a module, choose M here: the module + will be called ptp_kvm. + endmenu Index: kvm-ptpdriver/drivers/ptp/Makefile =================================================================== --- kvm-ptpdriver.orig/drivers/ptp/Makefile 2017-01-24 09:03:47.604586098 -0200 +++ kvm-ptpdriver/drivers/ptp/Makefile 2017-01-24 09:05:06.322704125 -0200 @@ -6,3 +6,4 @@ obj-$(CONFIG_PTP_1588_CLOCK) += ptp.o obj-$(CONFIG_PTP_1588_CLOCK_IXP46X) += ptp_ixp46x.o obj-$(CONFIG_PTP_1588_CLOCK_PCH) += ptp_pch.o +obj-$(CONFIG_PTP_1588_CLOCK_KVM) += ptp_kvm.o Index: kvm-ptpdriver/drivers/ptp/ptp_kvm.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ kvm-ptpdriver/drivers/ptp/ptp_kvm.c 2017-01-24 09:05:06.322704125 -0200 @@ -0,0 +1,202 @@ +/* + * Virtual PTP 1588 clock for use with KVM guests + * + * Copyright (C) 2017 Red Hat Inc. + * + * 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. + * + */ +#include +#include +#include +#include +#include +#include +#include +#include +#include +#include + +#include + +struct kvm_ptp_clock { + struct ptp_clock *ptp_clock; + struct ptp_clock_info caps; +}; + +DEFINE_SPINLOCK(kvm_ptp_lock); + +static struct pvclock_vsyscall_time_info *hv_clock; + +static struct kvm_clock_offset clock_off; +static phys_addr_t clock_off_gpa; + +static int ptp_kvm_get_time_fn(ktime_t *device_time, + struct system_counterval_t *system_counter, + void *ctx) +{ + unsigned long ret; + struct timespec64 tspec; + unsigned version; + u8 flags; + int cpu; + struct pvclock_vcpu_time_info *src; + + preempt_disable_notrace(); + cpu = smp_processor_id(); + src = &hv_clock[cpu].pvti; + + spin_lock(&kvm_ptp_lock); + + do { + /* + * We are using a TSC value read in the hosts + * kvm_hc_clock_pairing handling. + * So any changes to tsc_to_system_mul + * and tsc_shift or any other pvclock + * data invalidate that measurement. + */ + version = pvclock_read_begin(src); + + ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, + clock_off_gpa, + KVM_CLOCK_PAIRING_WALLCLOCK); + if (ret != 0) { + pr_err("clock offset hypercall ret %lu\n", ret); + spin_unlock(&kvm_ptp_lock); + preempt_enable_notrace(); + return -EOPNOTSUPP; + } + + tspec.tv_sec = clock_off.sec; + tspec.tv_nsec = clock_off.nsec; + ret = __pvclock_read_cycles(src, clock_off.tsc); + flags = src->flags; + } while (pvclock_read_retry(src, version)); + + preempt_enable_notrace(); + + system_counter->cycles = ret; + system_counter->cs = &kvm_clock; + + *device_time = timespec_to_ktime(tspec); + + spin_unlock(&kvm_ptp_lock); + + return 0; +} + +static int ptp_kvm_getcrosststamp(struct ptp_clock_info *ptp, + struct system_device_crosststamp *xtstamp) +{ + return get_device_system_crosststamp(ptp_kvm_get_time_fn, NULL, + NULL, xtstamp); +} + +/* + * PTP clock operations + */ + +static int ptp_kvm_adjfreq(struct ptp_clock_info *ptp, s32 ppb) +{ + return -EOPNOTSUPP; +} + +static int ptp_kvm_adjtime(struct ptp_clock_info *ptp, s64 delta) +{ + return -EOPNOTSUPP; +} + +static int ptp_kvm_settime(struct ptp_clock_info *ptp, + const struct timespec64 *ts) +{ + return -EOPNOTSUPP; +} + +static int ptp_kvm_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts) +{ + unsigned long ret; + struct timespec64 tspec; + + spin_lock(&kvm_ptp_lock); + + ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, + clock_off_gpa, + KVM_CLOCK_PAIRING_WALLCLOCK); + if (ret != 0) { + pr_err("clock offset hypercall ret %lu\n", ret); + spin_unlock(&kvm_ptp_lock); + return -EOPNOTSUPP; + } + + tspec.tv_sec = clock_off.sec; + tspec.tv_nsec = clock_off.nsec; + spin_unlock(&kvm_ptp_lock); + + memcpy(ts, &tspec, sizeof(struct timespec64)); + + return 0; +} + +static int ptp_kvm_enable(struct ptp_clock_info *ptp, + struct ptp_clock_request *rq, int on) +{ + return -EOPNOTSUPP; +} + +static struct ptp_clock_info ptp_kvm_caps = { + .owner = THIS_MODULE, + .name = "KVM virtual PTP", + .max_adj = 0, + .n_ext_ts = 0, + .n_pins = 0, + .pps = 0, + .adjfreq = ptp_kvm_adjfreq, + .adjtime = ptp_kvm_adjtime, + .gettime64 = ptp_kvm_gettime, + .settime64 = ptp_kvm_settime, + .enable = ptp_kvm_enable, + .getcrosststamp = ptp_kvm_getcrosststamp, +}; + +/* module operations */ + +static struct kvm_ptp_clock kvm_ptp_clock; + +static void __exit ptp_kvm_exit(void) +{ + ptp_clock_unregister(kvm_ptp_clock.ptp_clock); +} + +static int __init ptp_kvm_init(void) +{ + clock_off_gpa = slow_virt_to_phys(&clock_off); + hv_clock = pvclock_pvti_cpu0_va(); + + if (!hv_clock) + return -ENODEV; + + kvm_ptp_clock.caps = ptp_kvm_caps; + + kvm_ptp_clock.ptp_clock = ptp_clock_register(&kvm_ptp_clock.caps, NULL); + + if (IS_ERR(kvm_ptp_clock.ptp_clock)) + return PTR_ERR(kvm_ptp_clock.ptp_clock); + + return 0; +} + +module_init(ptp_kvm_init); +module_exit(ptp_kvm_exit); + +MODULE_AUTHOR("Marcelo Tosatti "); +MODULE_DESCRIPTION("PTP clock using KVMCLOCK"); +MODULE_LICENSE("GPL");