// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * Virtual PTP 1588 clock for use with KVM guests
 *
 * Copyright (C) 2017 Red Hat Inc.
 */

#include <linux/device.h>
#include <linux/kernel.h>
#include <asm/pvclock.h>
#include <asm/kvmclock.h>
#include <linux/module.h>
#include <uapi/asm/kvm_para.h>
#include <uapi/linux/kvm_para.h>
#include <linux/ptp_clock_kernel.h>
#include <linux/ptp_kvm.h>
#include <linux/set_memory.h>

static phys_addr_t clock_pair_gpa;
static struct kvm_clock_pairing clock_pair_glbl;
static struct kvm_clock_pairing *clock_pair;

int kvm_arch_ptp_init(void)
{
        struct page *p;
        long ret;

        if (!kvm_para_available())
                return -EOPNOTSUPP;

        if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
                p = alloc_page(GFP_KERNEL | __GFP_ZERO);
                if (!p)
                        return -ENOMEM;

                clock_pair = page_address(p);
                ret = set_memory_decrypted((unsigned long)clock_pair, 1);
                if (ret) {
                        __free_page(p);
                        clock_pair = NULL;
                        goto nofree;
                }
        } else {
                clock_pair = &clock_pair_glbl;
        }

        clock_pair_gpa = slow_virt_to_phys(clock_pair);
        if (!pvclock_get_pvti_cpu0_va()) {
                ret = -EOPNOTSUPP;
                goto err;
        }

        ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING, clock_pair_gpa,
                             KVM_CLOCK_PAIRING_WALLCLOCK);
        if (ret == -KVM_ENOSYS) {
                ret = -EOPNOTSUPP;
                goto err;
        }

        return ret;

err:
        kvm_arch_ptp_exit();
nofree:
        return ret;
}

void kvm_arch_ptp_exit(void)
{
        if (cc_platform_has(CC_ATTR_GUEST_MEM_ENCRYPT)) {
                WARN_ON(set_memory_encrypted((unsigned long)clock_pair, 1));
                free_page((unsigned long)clock_pair);
                clock_pair = NULL;
        }
}

int kvm_arch_ptp_get_clock(struct timespec64 *ts)
{
        long ret;

        ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
                             clock_pair_gpa,
                             KVM_CLOCK_PAIRING_WALLCLOCK);
        if (ret != 0) {
                pr_err_ratelimited("clock offset hypercall ret %lu\n", ret);
                return -EOPNOTSUPP;
        }

        ts->tv_sec = clock_pair->sec;
        ts->tv_nsec = clock_pair->nsec;

        return 0;
}

int kvm_arch_ptp_get_crosststamp(u64 *cycle, struct timespec64 *tspec,
                              enum clocksource_ids *cs_id)
{
        struct pvclock_vcpu_time_info *src;
        unsigned int version;
        long ret;

        src = this_cpu_pvti();

        do {
                /*
                 * We are using a TSC value read in the hosts
                 * kvm_hc_clock_pairing handling.
                 * So any changes to tsc_to_system_mul
                 * and tsc_shift or any other pvclock
                 * data invalidate that measurement.
                 */
                version = pvclock_read_begin(src);

                ret = kvm_hypercall2(KVM_HC_CLOCK_PAIRING,
                                     clock_pair_gpa,
                                     KVM_CLOCK_PAIRING_WALLCLOCK);
                if (ret != 0) {
                        pr_err_ratelimited("clock pairing hypercall ret %lu\n", ret);
                        return -EOPNOTSUPP;
                }
                tspec->tv_sec = clock_pair->sec;
                tspec->tv_nsec = clock_pair->nsec;
                *cycle = __pvclock_read_cycles(src, clock_pair->tsc);
        } while (pvclock_read_retry(src, version));

        *cs_id = CSID_X86_KVM_CLK;

        return 0;
}