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#include <linux/set_memory.h>
 18
 19static phys_addr_t clock_pair_gpa;
 20static struct kvm_clock_pairing clock_pair_glbl;
 21static struct kvm_clock_pairing *clock_pair;
 22
 23int kvm_arch_ptp_init(void)
 24{
 25	struct page *p;
 26	long ret;
 27
 28	if (!kvm_para_available())
 29		return -EOPNOTSUPP;
 30
 31	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
 32		p = alloc_page(GFP_KERNEL | __GFP_ZERO);
 33		if (!p)
 34			return -ENOMEM;
 35
 36		clock_pair = page_address(p);
 37		ret = set_memory_decrypted((unsigned long)clock_pair, 1);
 38		if (ret) {
 39			__free_page(p);
 40			clock_pair = NULL;
 41			goto nofree;
 42		}
 43	} else {
 44		clock_pair = &clock_pair_glbl;
 45	}
 46
 47	clock_pair_gpa = slow_virt_to_phys(clock_pair);
 48	if (!pvclock_get_pvti_cpu0_va()) {
 49		ret = -EOPNOTSUPP;
 50		goto err;
 51	}
 52
 53	ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, clock_pair_gpa,
 54			     KVM_CLOCK_PAIRING_WALLCLOCK);
 55	if (ret == -KVM_ENOSYS) {
 56		ret = -EOPNOTSUPP;
 57		goto err;
 58	}
 59
 60	return ret;
 61
 62err:
 63	kvm_arch_ptp_exit();
 64nofree:
 65	return ret;
 66}
 67
 68void kvm_arch_ptp_exit(void)
 69{
 70	if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
 71		WARN_ON(set_memory_encrypted((unsigned long)clock_pair, 1));
 72		free_page((unsigned long)clock_pair);
 73		clock_pair = NULL;
 74	}
 75}
 76
 77int kvm_arch_ptp_get_clock(struct timespec64 *ts)
 78{
 79	long ret;
 80
 81	ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
 82			     clock_pair_gpa,
 83			     KVM_CLOCK_PAIRING_WALLCLOCK);
 84	if (ret != 0) {
 85		pr_err_ratelimited("clock offset hypercall ret %lu\n", ret);
 86		return -EOPNOTSUPP;
 87	}
 88
 89	ts->tv_sec = clock_pair->sec;
 90	ts->tv_nsec = clock_pair->nsec;
 91
 92	return 0;
 93}
 94
 95int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *tspec,
 96			      enum clocksource_ids *cs_id)
 97{
 98	struct pvclock_vcpu_time_info *src;
 99	unsigned int version;
100	long ret;
101
102	src = this_cpu_pvti();
103
104	do {
105		/*
106		 * We are using a TSC value read in the hosts
107		 * kvm_hc_clock_pairing handling.
108		 * So any changes to tsc_to_system_mul
109		 * and tsc_shift or any other pvclock
110		 * data invalidate that measurement.
111		 */
112		version = pvclock_read_begin(src);
113
114		ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
115				     clock_pair_gpa,
116				     KVM_CLOCK_PAIRING_WALLCLOCK);
117		if (ret != 0) {
118			pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
119			return -EOPNOTSUPP;
120		}
121		tspec->tv_sec = clock_pair->sec;
122		tspec->tv_nsec = clock_pair->nsec;
123		*cycle = __pvclock_read_cycles(src, clock_pair->tsc);
124	} while (pvclock_read_retry(src, version));
125
126	*cs_id = CSID_X86_KVM_CLK;
127
128	return 0;
129}