// SPDX-License-Identifier: GPL-2.0-only
/*
 * X86 specific Hyper-V initialization code.
 *
 * Copyright (C) 2016, Microsoft, Inc.
 *
 * Author : K. Y. Srinivasan <kys@microsoft.com>
 */

#include <linux/efi.h>
#include <linux/types.h>
#include <linux/bitfield.h>
#include <linux/io.h>
#include <asm/apic.h>
#include <asm/desc.h>
#include <asm/hypervisor.h>
#include <asm/hyperv-tlfs.h>
#include <asm/mshyperv.h>
#include <asm/idtentry.h>
#include <linux/kexec.h>
#include <linux/version.h>
#include <linux/vmalloc.h>
#include <linux/mm.h>
#include <linux/hyperv.h>
#include <linux/slab.h>
#include <linux/kernel.h>
#include <linux/cpuhotplug.h>
#include <linux/syscore_ops.h>
#include <clocksource/hyperv_timer.h>
#include <linux/highmem.h>

int hyperv_init_cpuhp;
u64 hv_current_partition_id = ~0ull;
EXPORT_SYMBOL_GPL(hv_current_partition_id);

void *hv_hypercall_pg;
EXPORT_SYMBOL_GPL(hv_hypercall_pg);

/* Storage to save the hypercall page temporarily for hibernation */
static void *hv_hypercall_pg_saved;

struct hv_vp_assist_page **hv_vp_assist_page;
EXPORT_SYMBOL_GPL(hv_vp_assist_page);

static int hv_cpu_init(unsigned int cpu)
{
        union hv_vp_assist_msr_contents msr = { 0 };
        struct hv_vp_assist_page **hvp = &hv_vp_assist_page[smp_processor_id()];
        int ret;

        ret = hv_common_cpu_init(cpu);
        if (ret)
                return ret;

        if (!hv_vp_assist_page)
                return 0;

        if (!*hvp) {
                if (hv_root_partition) {
                        /*
                         * For root partition we get the hypervisor provided VP assist
                         * page, instead of allocating a new page.
                         */
                        rdmsrl(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
                        *hvp = memremap(msr.pfn <<
                                        HV_X64_MSR_VP_ASSIST_PAGE_ADDRESS_SHIFT,
                                        PAGE_SIZE, MEMREMAP_WB);
                } else {
                        /*
                         * The VP assist page is an "overlay" page (see Hyper-V TLFS's
                         * Section 5.2.1 "GPA Overlay Pages"). Here it must be zeroed
                         * out to make sure we always write the EOI MSR in
                         * hv_apic_eoi_write() *after* the EOI optimization is disabled
                         * in hv_cpu_die(), otherwise a CPU may not be stopped in the
                         * case of CPU offlining and the VM will hang.
                         */
                        *hvp = __vmalloc(PAGE_SIZE, GFP_KERNEL | __GFP_ZERO);
                        if (*hvp)
                                msr.pfn = vmalloc_to_pfn(*hvp);
                }
                WARN_ON(!(*hvp));
                if (*hvp) {
                        msr.enable = 1;
                        wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
                }
        }

        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 privileges to make TSC frequency
         * change notifications work.
         */
        return ms_hyperv.features & HV_ACCESS_FREQUENCY_MSRS &&
                ms_hyperv.misc_features & HV_FEATURE_FREQUENCY_MSRS_AVAILABLE &&
                ms_hyperv.features & HV_ACCESS_REENLIGHTENMENT;
}

DEFINE_IDTENTRY_SYSVEC(sysvec_hyperv_reenlightenment)
{
        ack_APIC_irq();
        inc_irq_stat(irq_hv_reenlightenment_count);
        schedule_delayed_work(&hv_reenlightenment_work, HZ/10);
}

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;

        hv_common_cpu_die(cpu);

        if (hv_vp_assist_page && hv_vp_assist_page[cpu]) {
                union hv_vp_assist_msr_contents msr = { 0 };
                if (hv_root_partition) {
                        /*
                         * For root partition the VP assist page is mapped to
                         * hypervisor provided page, and thus we unmap the
                         * page here and nullify it, so that in future we have
                         * correct page address mapped in hv_cpu_init.
                         */
                        memunmap(hv_vp_assist_page[cpu]);
                        hv_vp_assist_page[cpu] = NULL;
                        rdmsrl(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
                        msr.enable = 0;
                }
                wrmsrl(HV_X64_MSR_VP_ASSIST_PAGE, msr.as_uint64);
        }

        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 reenlightenment notifications to some other online
                 * CPU or just disable the feature if there are no online CPUs
                 * left (happens on hibernation).
                 */
                new_cpu = cpumask_any_but(cpu_online_mask, cpu);

                if (new_cpu < nr_cpu_ids)
                        re_ctrl.target_vp = hv_vp_index[new_cpu];
                else
                        re_ctrl.enabled = 0;

                wrmsrl(HV_X64_MSR_REENLIGHTENMENT_CONTROL, *((u64 *)&re_ctrl));
        }

        return 0;
}

static int __init hv_pci_init(void)
{
        int gen2vm = efi_enabled(EFI_BOOT);

        /*
         * For Generation-2 VM, we exit from pci_arch_init() by returning 0.
         * The purpose is to suppress the harmless warning:
         * "PCI: Fatal: No config space access function found"
         */
        if (gen2vm)
                return 0;

        /* For Generation-1 VM, we'll proceed in pci_arch_init().  */
        return 1;
}

static int hv_suspend(void)
{
        union hv_x64_msr_hypercall_contents hypercall_msr;
        int ret;

        if (hv_root_partition)
                return -EPERM;

        /*
         * Reset the hypercall page as it is going to be invalidated
         * across hibernation. Setting hv_hypercall_pg to NULL ensures
         * that any subsequent hypercall operation fails safely instead of
         * crashing due to an access of an invalid page. The hypercall page
         * pointer is restored on resume.
         */
        hv_hypercall_pg_saved = hv_hypercall_pg;
        hv_hypercall_pg = NULL;

        /* Disable the hypercall page in the hypervisor */
        rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
        hypercall_msr.enable = 0;
        wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

        ret = hv_cpu_die(0);
        return ret;
}

static void hv_resume(void)
{
        union hv_x64_msr_hypercall_contents hypercall_msr;
        int ret;

        ret = hv_cpu_init(0);
        WARN_ON(ret);

        /* Re-enable the hypercall page */
        rdmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
        hypercall_msr.enable = 1;
        hypercall_msr.guest_physical_address =
                vmalloc_to_pfn(hv_hypercall_pg_saved);
        wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

        hv_hypercall_pg = hv_hypercall_pg_saved;
        hv_hypercall_pg_saved = NULL;

        /*
         * Reenlightenment notifications are disabled by hv_cpu_die(0),
         * reenable them here if hv_reenlightenment_cb was previously set.
         */
        if (hv_reenlightenment_cb)
                set_hv_tscchange_cb(hv_reenlightenment_cb);
}

/* Note: when the ops are called, only CPU0 is online and IRQs are disabled. */
static struct syscore_ops hv_syscore_ops = {
        .suspend        = hv_suspend,
        .resume         = hv_resume,
};

static void (* __initdata old_setup_percpu_clockev)(void);

static void __init hv_stimer_setup_percpu_clockev(void)
{
        /*
         * Ignore any errors in setting up stimer clockevents
         * as we can run with the LAPIC timer as a fallback.
         */
        (void)hv_stimer_alloc(false);

        /*
         * Still register the LAPIC timer, because the direct-mode STIMER is
         * not supported by old versions of Hyper-V. This also allows users
         * to switch to LAPIC timer via /sys, if they want to.
         */
        if (old_setup_percpu_clockev)
                old_setup_percpu_clockev();
}

static void __init hv_get_partition_id(void)
{
        struct hv_get_partition_id *output_page;
        u64 status;
        unsigned long flags;

        local_irq_save(flags);
        output_page = *this_cpu_ptr(hyperv_pcpu_output_arg);
        status = hv_do_hypercall(HVCALL_GET_PARTITION_ID, NULL, output_page);
        if (!hv_result_success(status)) {
                /* No point in proceeding if this failed */
                pr_err("Failed to get partition ID: %lld\n", status);
                BUG();
        }
        hv_current_partition_id = output_page->partition_id;
        local_irq_restore(flags);
}

/*
 * 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.
 * 3. Setup Hyper-V specific APIC entry points.
 */
void __init 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_MSR_HYPERCALL_AVAILABLE |
                HV_MSR_VP_INDEX_AVAILABLE;

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

        if (hv_common_init())
                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 common_free;
        }

        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_node_range(PAGE_SIZE, 1, VMALLOC_START,
                        VMALLOC_END, GFP_KERNEL, PAGE_KERNEL_ROX,
                        VM_FLUSH_RESET_PERMS, NUMA_NO_NODE,
                        __builtin_return_address(0));
        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;

        if (hv_root_partition) {
                struct page *pg;
                void *src, *dst;

                /*
                 * For the root partition, the hypervisor will set up its
                 * hypercall page. The hypervisor guarantees it will not show
                 * up in the root's address space. The root can't change the
                 * location of the hypercall page.
                 *
                 * Order is important here. We must enable the hypercall page
                 * so it is populated with code, then copy the code to an
                 * executable page.
                 */
                wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);

                pg = vmalloc_to_page(hv_hypercall_pg);
                dst = kmap(pg);
                src = memremap(hypercall_msr.guest_physical_address << PAGE_SHIFT, PAGE_SIZE,
                                MEMREMAP_WB);
                BUG_ON(!(src && dst));
                memcpy(dst, src, HV_HYP_PAGE_SIZE);
                memunmap(src);
                kunmap(pg);
        } else {
                hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg);
                wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);
        }

        /*
         * hyperv_init() is called before LAPIC is initialized: see
         * apic_intr_mode_init() -> x86_platform.apic_post_init() and
         * apic_bsp_setup() -> setup_local_APIC(). The direct-mode STIMER
         * depends on LAPIC, so hv_stimer_alloc() should be called from
         * x86_init.timers.setup_percpu_clockev.
         */
        old_setup_percpu_clockev = x86_init.timers.setup_percpu_clockev;
        x86_init.timers.setup_percpu_clockev = hv_stimer_setup_percpu_clockev;

        hv_apic_init();

        x86_init.pci.arch_init = hv_pci_init;

        register_syscore_ops(&hv_syscore_ops);

        hyperv_init_cpuhp = cpuhp;

        if (cpuid_ebx(HYPERV_CPUID_FEATURES) & HV_ACCESS_PARTITION_ID)
                hv_get_partition_id();

        BUG_ON(hv_root_partition && hv_current_partition_id == ~0ull);

#ifdef CONFIG_PCI_MSI
        /*
         * If we're running as root, we want to create our own PCI MSI domain.
         * We can't set this in hv_pci_init because that would be too late.
         */
        if (hv_root_partition)
                x86_init.irqs.create_pci_msi_domain = hv_create_pci_msi_domain;
#endif

        /* Query the VMs extended capability once, so that it can be cached. */
        hv_query_ext_cap(0);
        return;

remove_cpuhp_state:
        cpuhp_remove_state(cpuhp);
free_vp_assist_page:
        kfree(hv_vp_assist_page);
        hv_vp_assist_page = NULL;
common_free:
        hv_common_free();
}

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

        unregister_syscore_ops(&hv_syscore_ops);

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

        /*
         * Reset hypercall page reference before reset the page,
         * let hypercall operations fail safely rather than
         * panic the kernel for using invalid hypercall page
         */
        hv_hypercall_pg = NULL;

        /* 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);
}

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

        if (in_die && !panic_on_oops)
                return;

        /*
         * 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);

enum hv_isolation_type hv_get_isolation_type(void)
{
        if (!(ms_hyperv.priv_high & HV_ISOLATION))
                return HV_ISOLATION_TYPE_NONE;
        return FIELD_GET(HV_ISOLATION_TYPE, ms_hyperv.isolation_config_b);
}
EXPORT_SYMBOL_GPL(hv_get_isolation_type);

bool hv_is_isolation_supported(void)
{
        return hv_get_isolation_type() != HV_ISOLATION_TYPE_NONE;
}