Commit a0e136d4 authored by Marcelo Tosatti's avatar Marcelo Tosatti Committed by Paolo Bonzini

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: default avatarMarcelo Tosatti <mtosatti@redhat.com>
Acked-by: default avatarRichard Cochran <richardcochran@gmail.com>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent f4066c2b
......@@ -90,4 +90,16 @@ config PTP_1588_CLOCK_PCH
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 && X86
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
......@@ -6,3 +6,4 @@ ptp-y := ptp_clock.o ptp_chardev.o ptp_sysfs.o
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
/*
* 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 <linux/device.h>
#include <linux/err.h>
#include <linux/init.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <uapi/linux/kvm_para.h>
#include <asm/kvm_para.h>
#include <asm/pvclock.h>
#include <asm/kvmclock.h>
#include <uapi/asm/kvm_para.h>
#include <linux/ptp_clock_kernel.h>
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_pairing clock_pair;
static phys_addr_t clock_pair_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;
int cpu;
struct pvclock_vcpu_time_info *src;
spin_lock(&kvm_ptp_lock);
preempt_disable_notrace();
cpu = smp_processor_id();
src = &hv_clock[cpu].pvti;
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_pair_gpa,
KVM_CLOCK_PAIRING_WALLCLOCK);
if (ret != 0) {
pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
spin_unlock(&kvm_ptp_lock);
preempt_enable_notrace();
return -EOPNOTSUPP;
}
tspec.tv_sec = clock_pair.sec;
tspec.tv_nsec = clock_pair.nsec;
ret = __pvclock_read_cycles(src, clock_pair.tsc);
} while (pvclock_read_retry(src, version));
preempt_enable_notrace();
system_counter->cycles = ret;
system_counter->cs = &kvm_clock;
*device_time = timespec64_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_pair_gpa,
KVM_CLOCK_PAIRING_WALLCLOCK);
if (ret != 0) {
pr_err_ratelimited("clock offset hypercall ret %lu\n", ret);
spin_unlock(&kvm_ptp_lock);
return -EOPNOTSUPP;
}
tspec.tv_sec = clock_pair.sec;
tspec.tv_nsec = clock_pair.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_pair_gpa = slow_virt_to_phys(&clock_pair);
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 <mtosatti@redhat.com>");
MODULE_DESCRIPTION("PTP clock using KVMCLOCK");
MODULE_LICENSE("GPL");
Markdown is supported
0% or
You are about to add 0 people to the discussion. Proceed with caution.
Finish editing this message first!
Please register or to comment