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>
diff --git a/drivers/ptp/Kconfig b/drivers/ptp/Kconfig
index bdce332..384f661 100644
--- a/drivers/ptp/Kconfig
+++ b/drivers/ptp/Kconfig
@@ -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 && 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
diff --git a/drivers/ptp/Makefile b/drivers/ptp/Makefile
index 8b58597..5307361 100644
--- a/drivers/ptp/Makefile
+++ b/drivers/ptp/Makefile
@@ -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
diff --git a/drivers/ptp/ptp_kvm.c b/drivers/ptp/ptp_kvm.c
new file mode 100644
index 0000000..0a54e83
--- /dev/null
+++ b/drivers/ptp/ptp_kvm.c
@@ -0,0 +1,200 @@
+/*
+ * 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");
