drivers/ptp/ptp_kvm_x86.c

   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
   8 #include <linux/device.h>
   9 #include <linux/kernel.h>
  10 #include <asm/pvclock.h>
  11 #include <asm/kvmclock.h>
  12 #include <linux/module.h>
  13 #include <uapi/asm/kvm_para.h>
  14 #include <uapi/linux/kvm_para.h>
  15 #include <linux/ptp_clock_kernel.h>
  16 #include <linux/ptp_kvm.h>
  17
  18 struct pvclock_vsyscall_time_info *hv_clock;
  19
  20 static phys_addr_t clock_pair_gpa;
  21 static struct kvm_clock_pairing clock_pair;
  22
  23 int kvm_arch_ptp_init(void)
  24 {
  25         long ret;
  26
  27         if (!kvm_para_available())
  28                 return -ENODEV;
  29
  30         clock_pair_gpa = slow_virt_to_phys(&clock_pair);
  31         hv_clock = pvclock_get_pvti_cpu0_va();
  32         if (!hv_clock)
  33                 return -ENODEV;
  34
  35         ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, clock_pair_gpa,
  36                              KVM_CLOCK_PAIRING_WALLCLOCK);
  37         if (ret == -KVM_ENOSYS || ret == -KVM_EOPNOTSUPP)
  38                 return -ENODEV;
  39
  40         return 0;
  41 }
  42
  43 int kvm_arch_ptp_get_clock(struct timespec64 *ts)
  44 {
  45         long ret;
  46
  47         ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
  48                              clock_pair_gpa,
  49                              KVM_CLOCK_PAIRING_WALLCLOCK);
  50         if (ret != 0) {
  51                 pr_err_ratelimited("clock offset hypercall ret %lu\n", ret);
  52                 return -EOPNOTSUPP;
  53         }
  54
  55         ts->tv_sec = clock_pair.sec;
  56         ts->tv_nsec = clock_pair.nsec;
  57
  58         return 0;
  59 }
  60
  61 int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *tspec,
  62                               struct clocksource **cs)
  63 {
  64         struct pvclock_vcpu_time_info *src;
  65         unsigned int version;
  66         long ret;
  67         int cpu;
  68
  69         cpu = smp_processor_id();
  70         src = &hv_clock[cpu].pvti;
  71
  72         do {
  73                 /*
  74                  * We are using a TSC value read in the hosts
  75                  * kvm_hc_clock_pairing handling.
  76                  * So any changes to tsc_to_system_mul
  77                  * and tsc_shift or any other pvclock
  78                  * data invalidate that measurement.
  79                  */
  80                 version = pvclock_read_begin(src);
  81
  82                 ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
  83                                      clock_pair_gpa,
  84                                      KVM_CLOCK_PAIRING_WALLCLOCK);
  85                 if (ret != 0) {
  86                         pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
  87                         return -EOPNOTSUPP;
  88                 }
  89                 tspec->tv_sec = clock_pair.sec;
  90                 tspec->tv_nsec = clock_pair.nsec;
  91                 *cycle = __pvclock_read_cycles(src, clock_pair.tsc);
  92         } while (pvclock_read_retry(src, version));
  93
  94         *cs = &kvm_clock;
  95
  96         return 0;
  97 }