drivers/ptp/ptp_kvm_x86.c

0001 // SPDX-License-Identifier: GPL-2.0-or-later
0002 /*
0003  * Virtual PTP 1588 clock for use with KVM guests
0004  *
0005  * Copyright (C) 2017 Red Hat Inc.
0006  */
0007
0008 #include <linux/device.h>
0009 #include <linux/kernel.h>
0010 #include <asm/pvclock.h>
0011 #include <asm/kvmclock.h>
0012 #include <linux/module.h>
0013 #include <uapi/asm/kvm_para.h>
0014 #include <uapi/linux/kvm_para.h>
0015 #include <linux/ptp_clock_kernel.h>
0016 #include <linux/ptp_kvm.h>
0017
0018 static phys_addr_t clock_pair_gpa;
0019 static struct kvm_clock_pairing clock_pair;
0020
0021 int kvm_arch_ptp_init(void)
0022 {
0023     long ret;
0024
0025     if (!kvm_para_available())
0026         return -ENODEV;
0027
0028     clock_pair_gpa = slow_virt_to_phys(&clock_pair);
0029     if (!pvclock_get_pvti_cpu0_va())
0030         return -ENODEV;
0031
0032     ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, clock_pair_gpa,
0033                  KVM_CLOCK_PAIRING_WALLCLOCK);
0034     if (ret == -KVM_ENOSYS)
0035         return -ENODEV;
0036
0037     return ret;
0038 }
0039
0040 int kvm_arch_ptp_get_clock(struct timespec64 *ts)
0041 {
0042     long ret;
0043
0044     ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
0045                  clock_pair_gpa,
0046                  KVM_CLOCK_PAIRING_WALLCLOCK);
0047     if (ret != 0) {
0048         pr_err_ratelimited("clock offset hypercall ret %lu\n", ret);
0049         return -EOPNOTSUPP;
0050     }
0051
0052     ts->tv_sec = clock_pair.sec;
0053     ts->tv_nsec = clock_pair.nsec;
0054
0055     return 0;
0056 }
0057
0058 int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *tspec,
0059                   struct clocksource **cs)
0060 {
0061     struct pvclock_vcpu_time_info *src;
0062     unsigned int version;
0063     long ret;
0064
0065     src = this_cpu_pvti();
0066
0067     do {
0068         /*
0069          * We are using a TSC value read in the hosts
0070          * kvm_hc_clock_pairing handling.
0071          * So any changes to tsc_to_system_mul
0072          * and tsc_shift or any other pvclock
0073          * data invalidate that measurement.
0074          */
0075         version = pvclock_read_begin(src);
0076
0077         ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
0078                      clock_pair_gpa,
0079                      KVM_CLOCK_PAIRING_WALLCLOCK);
0080         if (ret != 0) {
0081             pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
0082             return -EOPNOTSUPP;
0083         }
0084         tspec->tv_sec = clock_pair.sec;
0085         tspec->tv_nsec = clock_pair.nsec;
0086         *cycle = __pvclock_read_cycles(src, clock_pair.tsc);
0087     } while (pvclock_read_retry(src, version));
0088
0089     *cs = &kvm_clock;
0090
0091     return 0;
0092 }