/*
 * X86 specific Hyper-V initialization code.
 *
 * Copyright (C) 2016, Microsoft, Inc.
 *
 * Author : K. Y. Srinivasan <kys@microsoft.com>
 *
 * This program is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 as published
 * by the Free Software Foundation.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE, GOOD TITLE or
 * NON INFRINGEMENT.  See the GNU General Public License for more
 * details.
 *
 */

#include <linux/types.h>
#include <asm/apic.h>
#include <asm/desc.h>
#include <asm/hypervisor.h>
#include <asm/hyperv-tlfs.h>
#include <asm/mshyperv.h>
#include <linux/version.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/clockchips.h>
#include <linux/hyperv.h>
#include <linux/slab.h>
#include <linux/cpuhotplug.h>

#ifdef CONFIG_HYPERV_TSCPAGE

static struct ms_hyperv_tsc_page *tsc_pg;

struct ms_hyperv_tsc_page *hv_get_tsc_page(void)
{
        return tsc_pg;
}
EXPORT_SYMBOL_GPL(hv_get_tsc_page);

static u64 read_hv_clock_tsc(struct clocksource *arg)
{
        u64 current_tick = hv_read_tsc_page(tsc_pg);

        if (current_tick == U64_MAX)
                rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);

        return current_tick;
}

static struct clocksource hyperv_cs_tsc = {
                .name           = "hyperv_clocksource_tsc_page",
                .rating         = 400,
                .read           = read_hv_clock_tsc,
                .mask           = CLOCKSOURCE_MASK(64),
                .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
};
#endif

static u64 read_hv_clock_msr(struct clocksource *arg)
{
        u64 current_tick;
        /*
         * Read the partition counter to get the current tick count. This count
         * is set to 0 when the partition is created and is incremented in
         * 100 nanosecond units.
         */
        rdmsrl(HV_X64_MSR_TIME_REF_COUNT, current_tick);
        return current_tick;
}

static struct clocksource hyperv_cs_msr = {
        .name           = "hyperv_clocksource_msr",
        .rating         = 400,
        .read           = read_hv_clock_msr,
        .mask           = CLOCKSOURCE_MASK(64),
        .flags          = CLOCK_SOURCE_IS_CONTINUOUS,
};

void *hv_hypercall_pg;
EXPORT_SYMBOL_GPL(hv_hypercall_pg);
struct clocksource *hyperv_cs;
EXPORT_SYMBOL_GPL(hyperv_cs);

u32 *hv_vp_index;
EXPORT_SYMBOL_GPL(hv_vp_index);

struct hv_vp_assist_page **hv_vp_assist_page;
EXPORT_SYMBOL_GPL(hv_vp_assist_page);

u32 hv_max_vp_index;

static int hv_cpu_init(unsigned int cpu)
{
        u64 msr_vp_index;
        struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];

        hv_get_vp_index(msr_vp_index);

        hv_vp_index[smp_processor_id()] = msr_vp_index;

        if (msr_vp_index > hv_max_vp_index)
                hv_max_vp_index = msr_vp_index;

        if (!hv_vp_assist_page)
                return 0;

        if (!*hvp)
                *hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL);

        if (*hvp) {
                u64 val;

                val = vmalloc_to_pfn(*hvp);
                val = (val << HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT) |
                        HV_X64_MSR_VP_ASSIST_PAGE_ENABLE;

                wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, val);
        }

        return 0;
}

static void (*hv_reenlightenment_cb)(void);

static void hv_reenlightenment_notify(struct work_struct *dummy)
{
        struct hv_tsc_emulation_status emu_status;

        rdmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);

        /* Don't issue the callback if TSC accesses are not emulated */
        if (hv_reenlightenment_cb && emu_status.inprogress)
                hv_reenlightenment_cb();
}
static DECLARE_DELAYED_WORK(hv_reenlightenment_work, hv_reenlightenment_notify);

void hyperv_stop_tsc_emulation(void)
{
        u64 freq;
        struct hv_tsc_emulation_status emu_status;

        rdmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);
        emu_status.inprogress = 0;
        wrmsrl(HV_X64_MSR_TSC_EMULATION_STATUS, *(u64 *)&emu_status);

        rdmsrl(HV_X64_MSR_TSC_FREQUENCY, freq);
        tsc_khz = div64_u64(freq, 1000);
}
EXPORT_SYMBOL_GPL(hyperv_stop_tsc_emulation);

static inline bool hv_reenlightenment_available(void)
{
        /*
         * Check for required features and priviliges to make TSC frequency
         * change notifications work.
         */
        return ms_hyperv.features & HV_X64_ACCESS_FREQUENCY_MSRS &&
                ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE &&
                ms_hyperv.features & HV_X64_ACCESS_REENLIGHTENMENT;
}

__visible void __irq_entry hyperv_reenlightenment_intr(struct pt_regs *regs)
{
        entering_ack_irq();

        inc_irq_stat(irq_hv_reenlightenment_count);

        schedule_delayed_work(&hv_reenlightenment_work, HZ/10);

        exiting_irq();
}

void set_hv_tscchange_cb(void (*cb)(void))
{
        struct hv_reenlightenment_control re_ctrl = {
                .vector = HYPERV_REENLIGHTENMENT_VECTOR,
                .enabled = 1,
                .target_vp = hv_vp_index[smp_processor_id()]
        };
        struct hv_tsc_emulation_control emu_ctrl = {.enabled = 1};

        if (!hv_reenlightenment_available()) {
                pr_warn("Hyper-V: reenlightenment support is unavailable\n");
                return;
        }

        hv_reenlightenment_cb = cb;

        /* Make sure callback is registered before we write to MSRs */
        wmb();

        wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));
        wrmsrl(HV_X64_MSR_TSC_EMULATION_CONTROL, *((u64 *)&emu_ctrl));
}
EXPORT_SYMBOL_GPL(set_hv_tscchange_cb);

void clear_hv_tscchange_cb(void)
{
        struct hv_reenlightenment_control re_ctrl;

        if (!hv_reenlightenment_available())
                return;

        rdmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *(u64 *)&re_ctrl);
        re_ctrl.enabled = 0;
        wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *(u64 *)&re_ctrl);

        hv_reenlightenment_cb = NULL;
}
EXPORT_SYMBOL_GPL(clear_hv_tscchange_cb);

static int hv_cpu_die(unsigned int cpu)
{
        struct hv_reenlightenment_control re_ctrl;
        unsigned int new_cpu;

        if (hv_vp_assist_page && hv_vp_assist_page[cpu])
                wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, 0);

        if (hv_reenlightenment_cb == NULL)
                return 0;

        rdmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));
        if (re_ctrl.target_vp == hv_vp_index[cpu]) {
                /* Reassign to some other online CPU */
                new_cpu = cpumask_any_but(cpu_online_mask, cpu);

                re_ctrl.target_vp = hv_vp_index[new_cpu];
                wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));
        }

        return 0;
}

/*
 * This function is to be invoked early in the boot sequence after the
 * hypervisor has been detected.
 *
 * 1. Setup the hypercall page.
 * 2. Register Hyper-V specific clocksource.
 */
void hyperv_init(void)
{
        u64 guest_id, required_msrs;
        union hv_x64_msr_hypercall_contents hypercall_msr;
        int cpuhp;

        if (x86_hyper_type != X86_HYPER_MS_HYPERV)
                return;

        /* Absolutely required MSRs */
        required_msrs = HV_X64_MSR_HYPERCALL_AVAILABLE |
                HV_X64_MSR_VP_INDEX_AVAILABLE;

        if ((ms_hyperv.features & required_msrs) != required_msrs)
                return;

        /* Allocate percpu VP index */
        hv_vp_index = kmalloc_array(num_possible_cpus(), sizeof(*hv_vp_index),
                                    GFP_KERNEL);
        if (!hv_vp_index)
                return;

        hv_vp_assist_page = kcalloc(num_possible_cpus(),
                                    sizeof(*hv_vp_assist_page), GFP_KERNEL);
        if (!hv_vp_assist_page) {
                ms_hyperv.hints &= ~HV_X64_ENLIGHTENED_VMCS_RECOMMENDED;
                goto free_vp_index;
        }

        cpuhp = cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/hyperv_init:online",
                                  hv_cpu_init, hv_cpu_die);
        if (cpuhp < 0)
                goto free_vp_assist_page;

        /*
         * Setup the hypercall page and enable hypercalls.
         * 1. Register the guest ID
         * 2. Enable the hypercall and register the hypercall page
         */
        guest_id = generate_guest_id(0, LINUX_VERSION_CODE, 0);
        wrmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id);

        hv_hypercall_pg  = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL_RX);
        if (hv_hypercall_pg == NULL) {
                wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
                goto remove_cpuhp_state;
        }

        rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
        hypercall_msr.enable = 1;
        hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
        wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

        hyper_alloc_mmu();

        /*
         * Register Hyper-V specific clocksource.
         */
#ifdef CONFIG_HYPERV_TSCPAGE
        if (ms_hyperv.features & HV_X64_MSR_REFERENCE_TSC_AVAILABLE) {
                union hv_x64_msr_hypercall_contents tsc_msr;

                tsc_pg = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL);
                if (!tsc_pg)
                        goto register_msr_cs;

                hyperv_cs = &hyperv_cs_tsc;

                rdmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);

                tsc_msr.enable = 1;
                tsc_msr.guest_physical_address = vmalloc_to_pfn(tsc_pg);

                wrmsrl(HV_X64_MSR_REFERENCE_TSC, tsc_msr.as_uint64);

                hyperv_cs_tsc.archdata.vclock_mode = VCLOCK_HVCLOCK;

                clocksource_register_hz(&hyperv_cs_tsc, NSEC_PER_SEC/100);
                return;
        }
register_msr_cs:
#endif
        /*
         * For 32 bit guests just use the MSR based mechanism for reading
         * the partition counter.
         */

        hyperv_cs = &hyperv_cs_msr;
        if (ms_hyperv.features & HV_X64_MSR_TIME_REF_COUNT_AVAILABLE)
                clocksource_register_hz(&hyperv_cs_msr, NSEC_PER_SEC/100);

        return;

remove_cpuhp_state:
        cpuhp_remove_state(cpuhp);
free_vp_assist_page:
        kfree(hv_vp_assist_page);
        hv_vp_assist_page = NULL;
free_vp_index:
        kfree(hv_vp_index);
        hv_vp_index = NULL;
}

/*
 * This routine is called before kexec/kdump, it does the required cleanup.
 */
void hyperv_cleanup(void)
{
        union hv_x64_msr_hypercall_contents hypercall_msr;

        /* Reset our OS id */
        wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);

        /* Reset the hypercall page */
        hypercall_msr.as_uint64 = 0;
        wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

        /* Reset the TSC page */
        hypercall_msr.as_uint64 = 0;
        wrmsrl(HV_X64_MSR_REFERENCE_TSC, hypercall_msr.as_uint64);
}
EXPORT_SYMBOL_GPL(hyperv_cleanup);

void hyperv_report_panic(struct pt_regs *regs, long err)
{
        static bool panic_reported;
        u64 guest_id;

        /*
         * We prefer to report panic on 'die' chain as we have proper
         * registers to report, but if we miss it (e.g. on BUG()) we need
         * to report it on 'panic'.
         */
        if (panic_reported)
                return;
        panic_reported = true;

        rdmsrl(HV_X64_MSR_GUEST_OS_ID, guest_id);

        wrmsrl(HV_X64_MSR_CRASH_P0, err);
        wrmsrl(HV_X64_MSR_CRASH_P1, guest_id);
        wrmsrl(HV_X64_MSR_CRASH_P2, regs->ip);
        wrmsrl(HV_X64_MSR_CRASH_P3, regs->ax);
        wrmsrl(HV_X64_MSR_CRASH_P4, regs->sp);

        /*
         * Let Hyper-V know there is crash data available
         */
        wrmsrl(HV_X64_MSR_CRASH_CTL, HV_CRASH_CTL_CRASH_NOTIFY);
}
EXPORT_SYMBOL_GPL(hyperv_report_panic);

bool hv_is_hyperv_initialized(void)
{
        union hv_x64_msr_hypercall_contents hypercall_msr;

        /*
         * Ensure that we're really on Hyper-V, and not a KVM or Xen
         * emulation of Hyper-V
         */
        if (x86_hyper_type != X86_HYPER_MS_HYPERV)
                return false;

        /*
         * Verify that earlier initialization succeeded by checking
         * that the hypercall page is setup
         */
        hypercall_msr.as_uint64 = 0;
        rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

        return hypercall_msr.enable;
}
EXPORT_SYMBOL_GPL(hv_is_hyperv_initialized);