1// SPDX-License-Identifier: GPL-2.0-or-later
  2/*
  3 * Virtual PTP 1588 clock for use with KVM guests
  4 *
  5 * Copyright (C) 2017 Red Hat Inc.
  6 */
  7#include <linux/device.h>
  8#include <linux/err.h>
  9#include <linux/init.h>
 10#include <linux/kernel.h>
 11#include <linux/module.h>
 12#include <uapi/linux/kvm_para.h>
 13#include <asm/kvm_para.h>
 14#include <asm/pvclock.h>
 15#include <asm/kvmclock.h>
 16#include <uapi/asm/kvm_para.h>
 17
 18#include <linux/ptp_clock_kernel.h>
 19
 20struct kvm_ptp_clock {
 21	struct ptp_clock *ptp_clock;
 22	struct ptp_clock_info caps;
 23};
 24
 25static DEFINE_SPINLOCK(kvm_ptp_lock);
 26
 27static struct pvclock_vsyscall_time_info *hv_clock;
 28
 29static struct kvm_clock_pairing clock_pair;
 30static phys_addr_t clock_pair_gpa;
 31
 32static int ptp_kvm_get_time_fn(ktime_t *device_time,
 33			       struct system_counterval_t *system_counter,
 34			       void *ctx)
 35{
 36	unsigned long ret;
 37	struct timespec64 tspec;
 38	unsigned version;
 39	int cpu;
 40	struct pvclock_vcpu_time_info *src;
 41
 42	spin_lock(&kvm_ptp_lock);
 43
 44	preempt_disable_notrace();
 45	cpu = smp_processor_id();
 46	src = &hv_clock[cpu].pvti;
 47
 48	do {
 49		/*
 50		 * We are using a TSC value read in the hosts
 51		 * kvm_hc_clock_pairing handling.
 52		 * So any changes to tsc_to_system_mul
 53		 * and tsc_shift or any other pvclock
 54		 * data invalidate that measurement.
 55		 */
 56		version = pvclock_read_begin(src);
 57
 58		ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
 59				     clock_pair_gpa,
 60				     KVM_CLOCK_PAIRING_WALLCLOCK);
 61		if (ret != 0) {
 62			pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
 63			spin_unlock(&kvm_ptp_lock);
 64			preempt_enable_notrace();
 65			return -EOPNOTSUPP;
 66		}
 67
 68		tspec.tv_sec = clock_pair.sec;
 69		tspec.tv_nsec = clock_pair.nsec;
 70		ret = __pvclock_read_cycles(src, clock_pair.tsc);
 71	} while (pvclock_read_retry(src, version));
 72
 73	preempt_enable_notrace();
 74
 75	system_counter->cycles = ret;
 76	system_counter->cs = &kvm_clock;
 77
 78	*device_time = timespec64_to_ktime(tspec);
 79
 80	spin_unlock(&kvm_ptp_lock);
 81
 82	return 0;
 83}
 84
 85static int ptp_kvm_getcrosststamp(struct ptp_clock_info *ptp,
 86				  struct system_device_crosststamp *xtstamp)
 87{
 88	return get_device_system_crosststamp(ptp_kvm_get_time_fn, NULL,
 89					     NULL, xtstamp);
 90}
 91
 92/*
 93 * PTP clock operations
 94 */
 95
 96static int ptp_kvm_adjfreq(struct ptp_clock_info *ptp, s32 ppb)
 97{
 98	return -EOPNOTSUPP;
 99}
100
101static int ptp_kvm_adjtime(struct ptp_clock_info *ptp, s64 delta)
102{
103	return -EOPNOTSUPP;
104}
105
106static int ptp_kvm_settime(struct ptp_clock_info *ptp,
107			   const struct timespec64 *ts)
108{
109	return -EOPNOTSUPP;
110}
111
112static int ptp_kvm_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
113{
114	unsigned long ret;
115	struct timespec64 tspec;
116
117	spin_lock(&kvm_ptp_lock);
118
119	ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
120			     clock_pair_gpa,
121			     KVM_CLOCK_PAIRING_WALLCLOCK);
122	if (ret != 0) {
123		pr_err_ratelimited("clock offset hypercall ret %lu\n", ret);
124		spin_unlock(&kvm_ptp_lock);
125		return -EOPNOTSUPP;
126	}
127
128	tspec.tv_sec = clock_pair.sec;
129	tspec.tv_nsec = clock_pair.nsec;
130	spin_unlock(&kvm_ptp_lock);
131
132	memcpy(ts, &tspec, sizeof(struct timespec64));
133
134	return 0;
135}
136
137static int ptp_kvm_enable(struct ptp_clock_info *ptp,
138			  struct ptp_clock_request *rq, int on)
139{
140	return -EOPNOTSUPP;
141}
142
143static const struct ptp_clock_info ptp_kvm_caps = {
144	.owner		= THIS_MODULE,
145	.name		= "KVM virtual PTP",
146	.max_adj	= 0,
147	.n_ext_ts	= 0,
148	.n_pins		= 0,
149	.pps		= 0,
150	.adjfreq	= ptp_kvm_adjfreq,
151	.adjtime	= ptp_kvm_adjtime,
152	.gettime64	= ptp_kvm_gettime,
153	.settime64	= ptp_kvm_settime,
154	.enable		= ptp_kvm_enable,
155	.getcrosststamp = ptp_kvm_getcrosststamp,
156};
157
158/* module operations */
159
160static struct kvm_ptp_clock kvm_ptp_clock;
161
162static void __exit ptp_kvm_exit(void)
163{
164	ptp_clock_unregister(kvm_ptp_clock.ptp_clock);
165}
166
167static int __init ptp_kvm_init(void)
168{
169	long ret;
170
171	if (!kvm_para_available())
172		return -ENODEV;
173
174	clock_pair_gpa = slow_virt_to_phys(&clock_pair);
175	hv_clock = pvclock_get_pvti_cpu0_va();
176
177	if (!hv_clock)
178		return -ENODEV;
179
180	ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, clock_pair_gpa,
181			KVM_CLOCK_PAIRING_WALLCLOCK);
182	if (ret == -KVM_ENOSYS || ret == -KVM_EOPNOTSUPP)
183		return -ENODEV;
184
185	kvm_ptp_clock.caps = ptp_kvm_caps;
186
187	kvm_ptp_clock.ptp_clock = ptp_clock_register(&kvm_ptp_clock.caps, NULL);
188
189	return PTR_ERR_OR_ZERO(kvm_ptp_clock.ptp_clock);
190}
191
192module_init(ptp_kvm_init);
193module_exit(ptp_kvm_exit);
194
195MODULE_AUTHOR("Marcelo Tosatti <mtosatti@redhat.com>");
196MODULE_DESCRIPTION("PTP clock using KVMCLOCK");
197MODULE_LICENSE("GPL");