// SPDX-License-Identifier: GPL-2.0-or-later
#include <linux/acpi.h>
#include <linux/cpu.h>
#include <linux/delay.h>
#include <linux/io.h>
#include <linux/kexec.h>
#include <linux/memblock.h>
#include <linux/pgtable.h>
#include <linux/sched/hotplug.h>
#include <asm/apic.h>
#include <asm/barrier.h>
#include <asm/init.h>
#include <asm/intel_pt.h>
#include <asm/nmi.h>
#include <asm/processor.h>
#include <asm/reboot.h>

/* Physical address of the Multiprocessor Wakeup Structure mailbox */
static u64 acpi_mp_wake_mailbox_paddr __ro_after_init;

/* Virtual address of the Multiprocessor Wakeup Structure mailbox */
static struct acpi_madt_multiproc_wakeup_mailbox *acpi_mp_wake_mailbox;

static u64 acpi_mp_pgd __ro_after_init;
static u64 acpi_mp_reset_vector_paddr __ro_after_init;

static void acpi_mp_stop_this_cpu(void)
{
        asm_acpi_mp_play_dead(acpi_mp_reset_vector_paddr, acpi_mp_pgd);
}

static void acpi_mp_play_dead(void)
{
        play_dead_common();
        asm_acpi_mp_play_dead(acpi_mp_reset_vector_paddr, acpi_mp_pgd);
}

static void acpi_mp_cpu_die(unsigned int cpu)
{
        u32 apicid = per_cpu(x86_cpu_to_apicid, cpu);
        unsigned long timeout;

        /*
         * Use TEST mailbox command to prove that BIOS got control over
         * the CPU before declaring it dead.
         *
         * BIOS has to clear 'command' field of the mailbox.
         */
        acpi_mp_wake_mailbox->apic_id = apicid;
        smp_store_release(&acpi_mp_wake_mailbox->command,
                          ACPI_MP_WAKE_COMMAND_TEST);

        /* Don't wait longer than a second. */
        timeout = USEC_PER_SEC;
        while (READ_ONCE(acpi_mp_wake_mailbox->command) && --timeout)
                udelay(1);

        if (!timeout)
                pr_err("Failed to hand over CPU %d to BIOS\n", cpu);
}

/* The argument is required to match type of x86_mapping_info::alloc_pgt_page */
static void __init *alloc_pgt_page(void *dummy)
{
        return memblock_alloc(PAGE_SIZE, PAGE_SIZE);
}

static void __init free_pgt_page(void *pgt, void *dummy)
{
        return memblock_free(pgt, PAGE_SIZE);
}

static int __init acpi_mp_setup_reset(u64 reset_vector)
{
        struct x86_mapping_info info = {
                .alloc_pgt_page = alloc_pgt_page,
                .free_pgt_page  = free_pgt_page,
                .page_flag      = __PAGE_KERNEL_LARGE_EXEC,
                .kernpg_flag    = _KERNPG_TABLE_NOENC,
        };
        unsigned long mstart, mend;
        pgd_t *pgd;

        pgd = alloc_pgt_page(NULL);
        if (!pgd)
                return -ENOMEM;

        for (int i = 0; i < nr_pfn_mapped; i++) {
                mstart = pfn_mapped[i].start << PAGE_SHIFT;
                mend   = pfn_mapped[i].end << PAGE_SHIFT;
                if (kernel_ident_mapping_init(&info, pgd, mstart, mend)) {
                        kernel_ident_mapping_free(&info, pgd);
                        return -ENOMEM;
                }
        }

        mstart = PAGE_ALIGN_DOWN(reset_vector);
        mend = mstart + PAGE_SIZE;
        if (kernel_ident_mapping_init(&info, pgd, mstart, mend)) {
                kernel_ident_mapping_free(&info, pgd);
                return -ENOMEM;
        }

        /*
         * Make sure asm_acpi_mp_play_dead() is present in the identity mapping
         * at the same place as in the kernel page tables.
         * asm_acpi_mp_play_dead() switches to the identity mapping and the
         * function must be present at the same spot in the virtual address space
         * before and after switching page tables.
         */
        info.offset = __START_KERNEL_map - phys_base;
        mstart = PAGE_ALIGN_DOWN(__pa(asm_acpi_mp_play_dead));
        mend = mstart + PAGE_SIZE;
        if (kernel_ident_mapping_init(&info, pgd, mstart, mend)) {
                kernel_ident_mapping_free(&info, pgd);
                return -ENOMEM;
        }

        smp_ops.play_dead = acpi_mp_play_dead;
        smp_ops.stop_this_cpu = acpi_mp_stop_this_cpu;
        smp_ops.cpu_die = acpi_mp_cpu_die;

        acpi_mp_reset_vector_paddr = reset_vector;
        acpi_mp_pgd = __pa(pgd);

        return 0;
}

static int acpi_wakeup_cpu(u32 apicid, unsigned long start_ip, unsigned int cpu)
{
        if (!acpi_mp_wake_mailbox_paddr) {
                pr_warn_once("No MADT mailbox: cannot bringup secondary CPUs. Booting with kexec?\n");
                return -EOPNOTSUPP;
        }

        /*
         * Remap mailbox memory only for the first call to acpi_wakeup_cpu().
         *
         * Wakeup of secondary CPUs is fully serialized in the core code.
         * No need to protect acpi_mp_wake_mailbox from concurrent accesses.
         */
        if (!acpi_mp_wake_mailbox) {
                acpi_mp_wake_mailbox = memremap(acpi_mp_wake_mailbox_paddr,
                                                sizeof(*acpi_mp_wake_mailbox),
                                                MEMREMAP_WB);
        }

        /*
         * Mailbox memory is shared between the firmware and OS. Firmware will
         * listen on mailbox command address, and once it receives the wakeup
         * command, the CPU associated with the given apicid will be booted.
         *
         * The value of 'apic_id' and 'wakeup_vector' must be visible to the
         * firmware before the wakeup command is visible.  smp_store_release()
         * ensures ordering and visibility.
         */
        acpi_mp_wake_mailbox->apic_id       = apicid;
        acpi_mp_wake_mailbox->wakeup_vector = start_ip;
        smp_store_release(&acpi_mp_wake_mailbox->command,
                          ACPI_MP_WAKE_COMMAND_WAKEUP);

        /*
         * Wait for the CPU to wake up.
         *
         * The CPU being woken up is essentially in a spin loop waiting to be
         * woken up. It should not take long for it wake up and acknowledge by
         * zeroing out ->command.
         *
         * ACPI specification doesn't provide any guidance on how long kernel
         * has to wait for a wake up acknowledgment. It also doesn't provide
         * a way to cancel a wake up request if it takes too long.
         *
         * In TDX environment, the VMM has control over how long it takes to
         * wake up secondary. It can postpone scheduling secondary vCPU
         * indefinitely. Giving up on wake up request and reporting error opens
         * possible attack vector for VMM: it can wake up a secondary CPU when
         * kernel doesn't expect it. Wait until positive result of the wake up
         * request.
         */
        while (READ_ONCE(acpi_mp_wake_mailbox->command))
                cpu_relax();

        return 0;
}

static void acpi_mp_disable_offlining(struct acpi_madt_multiproc_wakeup *mp_wake)
{
        cpu_hotplug_disable_offlining();

        /*
         * ACPI MADT doesn't allow to offline a CPU after it was onlined. This
         * limits kexec: the second kernel won't be able to use more than one CPU.
         *
         * To prevent a kexec kernel from onlining secondary CPUs invalidate the
         * mailbox address in the ACPI MADT wakeup structure which prevents a
         * kexec kernel to use it.
         *
         * This is safe as the booting kernel has the mailbox address cached
         * already and acpi_wakeup_cpu() uses the cached value to bring up the
         * secondary CPUs.
         *
         * Note: This is a Linux specific convention and not covered by the
         *       ACPI specification.
         */
        mp_wake->mailbox_address = 0;
}

int __init acpi_parse_mp_wake(union acpi_subtable_headers *header,
                              const unsigned long end)
{
        struct acpi_madt_multiproc_wakeup *mp_wake;

        mp_wake = (struct acpi_madt_multiproc_wakeup *)header;

        /*
         * Cannot use the standard BAD_MADT_ENTRY() to sanity check the @mp_wake
         * entry.  'sizeof (struct acpi_madt_multiproc_wakeup)' can be larger
         * than the actual size of the MP wakeup entry in ACPI table because the
         * 'reset_vector' is only available in the V1 MP wakeup structure.
         */
        if (!mp_wake)
                return -EINVAL;
        if (end - (unsigned long)mp_wake < ACPI_MADT_MP_WAKEUP_SIZE_V0)
                return -EINVAL;
        if (mp_wake->header.length < ACPI_MADT_MP_WAKEUP_SIZE_V0)
                return -EINVAL;

        acpi_table_print_madt_entry(&header->common);

        acpi_mp_wake_mailbox_paddr = mp_wake->mailbox_address;

        if (mp_wake->version >= ACPI_MADT_MP_WAKEUP_VERSION_V1 &&
            mp_wake->header.length >= ACPI_MADT_MP_WAKEUP_SIZE_V1) {
                if (acpi_mp_setup_reset(mp_wake->reset_vector)) {
                        pr_warn("Failed to setup MADT reset vector\n");
                        acpi_mp_disable_offlining(mp_wake);
                }
        } else {
                /*
                 * CPU offlining requires version 1 of the ACPI MADT wakeup
                 * structure.
                 */
                acpi_mp_disable_offlining(mp_wake);
        }

        apic_update_callback(wakeup_secondary_cpu_64, acpi_wakeup_cpu);

        return 0;
}