/*
 * 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/hypervisor.h>
#include <asm/hyperv.h>
#include <asm/mshyperv.h>
#include <linux/version.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/clockchips.h>


#ifdef CONFIG_X86_64

static struct ms_hyperv_tsc_page *tsc_pg;

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

        if (tsc_pg->tsc_sequence != 0) {
                /*
                 * Use the tsc page to compute the value.
                 */

                while (1) {
                        u64 tmp;
                        u32 sequence = tsc_pg->tsc_sequence;
                        u64 cur_tsc;
                        u64 scale = tsc_pg->tsc_scale;
                        s64 offset = tsc_pg->tsc_offset;

                        rdtscll(cur_tsc);
                        /* current_tick = ((cur_tsc *scale) >> 64) + offset */
                        asm("mulq %3"
                                : "=d" (current_tick), "=a" (tmp)
                                : "a" (cur_tsc), "r" (scale));

                        current_tick += offset;
                        if (tsc_pg->tsc_sequence == sequence)
                                return current_tick;

                        if (tsc_pg->tsc_sequence != 0)
                                continue;
                        /*
                         * Fallback using MSR method.
                         */
                        break;
                }
        }
        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,
};

static void *hypercall_pg;
struct clocksource *hyperv_cs;
EXPORT_SYMBOL_GPL(hyperv_cs);

/*
 * 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;
        union hv_x64_msr_hypercall_contents hypercall_msr;

        if (x86_hyper != &x86_hyper_ms_hyperv)
                return;

        /*
         * 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);

        hypercall_pg  = __vmalloc(PAGE_SIZE, GFP_KERNEL, PAGE_KERNEL_RX);
        if (hypercall_pg == NULL) {
                wrmsrl(HV_X64_MSR_GUEST_OS_ID, 0);
                return;
        }

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

        /*
         * Register Hyper-V specific clocksource.
         */
#ifdef CONFIG_X86_64
        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);
                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);
}

/*
 * 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);

/*
 * hv_do_hypercall- Invoke the specified hypercall
 */
u64 hv_do_hypercall(u64 control, void *input, void *output)
{
        u64 input_address = (input) ? virt_to_phys(input) : 0;
        u64 output_address = (output) ? virt_to_phys(output) : 0;
#ifdef CONFIG_X86_64
        u64 hv_status = 0;

        if (!hypercall_pg)
                return (u64)ULLONG_MAX;

        __asm__ __volatile__("mov %0, %%r8" : : "r" (output_address) : "r8");
        __asm__ __volatile__("call *%3" : "=a" (hv_status) :
                             "c" (control), "d" (input_address),
                             "m" (hypercall_pg));

        return hv_status;

#else

        u32 control_hi = control >> 32;
        u32 control_lo = control & 0xFFFFFFFF;
        u32 hv_status_hi = 1;
        u32 hv_status_lo = 1;
        u32 input_address_hi = input_address >> 32;
        u32 input_address_lo = input_address & 0xFFFFFFFF;
        u32 output_address_hi = output_address >> 32;
        u32 output_address_lo = output_address & 0xFFFFFFFF;

        if (!hypercall_pg)
                return (u64)ULLONG_MAX;

        __asm__ __volatile__ ("call *%8" : "=d"(hv_status_hi),
                              "=a"(hv_status_lo) : "d" (control_hi),
                              "a" (control_lo), "b" (input_address_hi),
                              "c" (input_address_lo), "D"(output_address_hi),
                              "S"(output_address_lo), "m" (hypercall_pg));

        return hv_status_lo | ((u64)hv_status_hi << 32);
#endif /* !x86_64 */
}
EXPORT_SYMBOL_GPL(hv_do_hypercall);

void hyperv_report_panic(struct pt_regs *regs)
{
        static bool panic_reported;

        /*
         * 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;

        wrmsrl(HV_X64_MSR_CRASH_P0, regs->ip);
        wrmsrl(HV_X64_MSR_CRASH_P1, regs->ax);
        wrmsrl(HV_X64_MSR_CRASH_P2, regs->bx);
        wrmsrl(HV_X64_MSR_CRASH_P3, regs->cx);
        wrmsrl(HV_X64_MSR_CRASH_P4, regs->dx);

        /*
         * 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_hypercall_page_setup(void)
{
        union hv_x64_msr_hypercall_contents hypercall_msr;

        /* Check if the hypercall page is setup */
        hypercall_msr.as_uint64 = 0;
        rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

        if (!hypercall_msr.enable)
                return false;

        return true;
}
EXPORT_SYMBOL_GPL(hv_is_hypercall_page_setup);