drivers/ptp/ptp_kvm.c

   1 /*
   2  * Virtual PTP 1588 clock for use with KVM guests
   3  *
   4  * Copyright (C) 2017 Red Hat Inc.
   5  *
   6  *  This program is free software; you can redistribute it and/or modify
   7  *  it under the terms of the GNU General Public License as published by
   8  *  the Free Software Foundation; either version 2 of the License, or
   9  *  (at your option) any later version.
  10  *
  11  *  This program is distributed in the hope that it will be useful,
  12  *  but WITHOUT ANY WARRANTY; without even the implied warranty of
  13  *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14  *  GNU General Public License for more details.
  15  *
  16  */
  17 #include <linux/device.h>
  18 #include <linux/err.h>
  19 #include <linux/init.h>
  20 #include <linux/kernel.h>
  21 #include <linux/module.h>
  22 #include <uapi/linux/kvm_para.h>
  23 #include <asm/kvm_para.h>
  24 #include <asm/pvclock.h>
  25 #include <asm/kvmclock.h>
  26 #include <uapi/asm/kvm_para.h>
  27
  28 #include <linux/ptp_clock_kernel.h>
  29
  30 struct kvm_ptp_clock {
  31         struct ptp_clock *ptp_clock;
  32         struct ptp_clock_info caps;
  33 };
  34
  35 DEFINE_SPINLOCK(kvm_ptp_lock);
  36
  37 static struct pvclock_vsyscall_time_info *hv_clock;
  38
  39 static struct kvm_clock_pairing clock_pair;
  40 static phys_addr_t clock_pair_gpa;
  41
  42 static int ptp_kvm_get_time_fn(ktime_t *device_time,
  43                                struct system_counterval_t *system_counter,
  44                                void *ctx)
  45 {
  46         unsigned long ret;
  47         struct timespec64 tspec;
  48         unsigned version;
  49         int cpu;
  50         struct pvclock_vcpu_time_info *src;
  51
  52         spin_lock(&kvm_ptp_lock);
  53
  54         preempt_disable_notrace();
  55         cpu = smp_processor_id();
  56         src = &hv_clock[cpu].pvti;
  57
  58         do {
  59                 /*
  60                  * We are using a TSC value read in the hosts
  61                  * kvm_hc_clock_pairing handling.
  62                  * So any changes to tsc_to_system_mul
  63                  * and tsc_shift or any other pvclock
  64                  * data invalidate that measurement.
  65                  */
  66                 version = pvclock_read_begin(src);
  67
  68                 ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
  69                                      clock_pair_gpa,
  70                                      KVM_CLOCK_PAIRING_WALLCLOCK);
  71                 if (ret != 0) {
  72                         pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
  73                         spin_unlock(&kvm_ptp_lock);
  74                         preempt_enable_notrace();
  75                         return -EOPNOTSUPP;
  76                 }
  77
  78                 tspec.tv_sec = clock_pair.sec;
  79                 tspec.tv_nsec = clock_pair.nsec;
  80                 ret = __pvclock_read_cycles(src, clock_pair.tsc);
  81         } while (pvclock_read_retry(src, version));
  82
  83         preempt_enable_notrace();
  84
  85         system_counter->cycles = ret;
  86         system_counter->cs = &kvm_clock;
  87
  88         *device_time = timespec64_to_ktime(tspec);
  89
  90         spin_unlock(&kvm_ptp_lock);
  91
  92         return 0;
  93 }
  94
  95 static int ptp_kvm_getcrosststamp(struct ptp_clock_info *ptp,
  96                                   struct system_device_crosststamp *xtstamp)
  97 {
  98         return get_device_system_crosststamp(ptp_kvm_get_time_fn, NULL,
  99                                              NULL, xtstamp);
 100 }
 101
 102 /*
 103  * PTP clock operations
 104  */
 105
 106 static int ptp_kvm_adjfreq(struct ptp_clock_info *ptp, s32 ppb)
 107 {
 108         return -EOPNOTSUPP;
 109 }
 110
 111 static int ptp_kvm_adjtime(struct ptp_clock_info *ptp, s64 delta)
 112 {
 113         return -EOPNOTSUPP;
 114 }
 115
 116 static int ptp_kvm_settime(struct ptp_clock_info *ptp,
 117                            const struct timespec64 *ts)
 118 {
 119         return -EOPNOTSUPP;
 120 }
 121
 122 static int ptp_kvm_gettime(struct ptp_clock_info *ptp, struct timespec64 *ts)
 123 {
 124         unsigned long ret;
 125         struct timespec64 tspec;
 126
 127         spin_lock(&kvm_ptp_lock);
 128
 129         ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
 130                              clock_pair_gpa,
 131                              KVM_CLOCK_PAIRING_WALLCLOCK);
 132         if (ret != 0) {
 133                 pr_err_ratelimited("clock offset hypercall ret %lu\n", ret);
 134                 spin_unlock(&kvm_ptp_lock);
 135                 return -EOPNOTSUPP;
 136         }
 137
 138         tspec.tv_sec = clock_pair.sec;
 139         tspec.tv_nsec = clock_pair.nsec;
 140         spin_unlock(&kvm_ptp_lock);
 141
 142         memcpy(ts, &tspec, sizeof(struct timespec64));
 143
 144         return 0;
 145 }
 146
 147 static int ptp_kvm_enable(struct ptp_clock_info *ptp,
 148                           struct ptp_clock_request *rq, int on)
 149 {
 150         return -EOPNOTSUPP;
 151 }
 152
 153 static struct ptp_clock_info ptp_kvm_caps = {
 154         .owner          = THIS_MODULE,
 155         .name           = "KVM virtual PTP",
 156         .max_adj        = 0,
 157         .n_ext_ts       = 0,
 158         .n_pins         = 0,
 159         .pps            = 0,
 160         .adjfreq        = ptp_kvm_adjfreq,
 161         .adjtime        = ptp_kvm_adjtime,
 162         .gettime64      = ptp_kvm_gettime,
 163         .settime64      = ptp_kvm_settime,
 164         .enable         = ptp_kvm_enable,
 165         .getcrosststamp = ptp_kvm_getcrosststamp,
 166 };
 167
 168 /* module operations */
 169
 170 static struct kvm_ptp_clock kvm_ptp_clock;
 171
 172 static void __exit ptp_kvm_exit(void)
 173 {
 174         ptp_clock_unregister(kvm_ptp_clock.ptp_clock);
 175 }
 176
 177 static int __init ptp_kvm_init(void)
 178 {
 179         long ret;
 180
 181         clock_pair_gpa = slow_virt_to_phys(&clock_pair);
 182         hv_clock = pvclock_pvti_cpu0_va();
 183
 184         if (!hv_clock)
 185                 return -ENODEV;
 186
 187         ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, clock_pair_gpa,
 188                         KVM_CLOCK_PAIRING_WALLCLOCK);
 189         if (ret == -KVM_ENOSYS || ret == -KVM_EOPNOTSUPP)
 190                 return -ENODEV;
 191
 192         kvm_ptp_clock.caps = ptp_kvm_caps;
 193
 194         kvm_ptp_clock.ptp_clock = ptp_clock_register(&kvm_ptp_clock.caps, NULL);
 195
 196         if (IS_ERR(kvm_ptp_clock.ptp_clock))
 197                 return PTR_ERR(kvm_ptp_clock.ptp_clock);
 198
 199         return 0;
 200 }
 201
 202 module_init(ptp_kvm_init);
 203 module_exit(ptp_kvm_exit);
 204
 205 MODULE_AUTHOR("Marcelo Tosatti <mtosatti@redhat.com>");
 206 MODULE_DESCRIPTION("PTP clock using KVMCLOCK");
 207 MODULE_LICENSE("GPL");