Donate to e Foundation | Murena handsets with /e/OS | Own a part of Murena! Learn more

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

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

drivers/ptp/Kconfig

+12 −0
Original line number Diff line number Diff line
@@ -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

drivers/ptp/Makefile

+1 −0
Original line number Diff line number Diff line
@@ -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

drivers/ptp/ptp_kvm.c

0 → 100644
+200 −0
Original line number Diff line number Diff line 
/*

 * 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");