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