drm/panthor: Don't add write fences to the shared BOs

[drm/drm-misc.git] / arch / x86 / kernel / cpu / microcode / core.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 * CPU Microcode Update Driver for Linux
 *
 * Copyright (C) 2000-2006 Tigran Aivazian <aivazian.tigran@gmail.com>
 *            2006      Shaohua Li <shaohua.li@intel.com>
 *            2013-2016 Borislav Petkov <bp@alien8.de>
 *
 * X86 CPU microcode early update for Linux:
 *
 *      Copyright (C) 2012 Fenghua Yu <fenghua.yu@intel.com>
 *                         H Peter Anvin" <hpa@zytor.com>
 *                (C) 2015 Borislav Petkov <bp@alien8.de>
 *
 * This driver allows to upgrade microcode on x86 processors.
 */

#define pr_fmt(fmt) "microcode: " fmt

#include <linux/platform_device.h>
#include <linux/stop_machine.h>
#include <linux/syscore_ops.h>
#include <linux/miscdevice.h>
#include <linux/capability.h>
#include <linux/firmware.h>
#include <linux/cpumask.h>
#include <linux/kernel.h>
#include <linux/delay.h>
#include <linux/mutex.h>
#include <linux/cpu.h>
#include <linux/nmi.h>
#include <linux/fs.h>
#include <linux/mm.h>

#include <asm/apic.h>
#include <asm/cpu_device_id.h>
#include <asm/perf_event.h>
#include <asm/processor.h>
#include <asm/cmdline.h>
#include <asm/setup.h>

#include "internal.h"

static struct microcode_ops     *microcode_ops;
bool dis_ucode_ldr = true;

bool force_minrev = IS_ENABLED(CONFIG_MICROCODE_LATE_FORCE_MINREV);
module_param(force_minrev, bool, S_IRUSR | S_IWUSR);

/*
 * Synchronization.
 *
 * All non cpu-hotplug-callback call sites use:
 *
 * - cpus_read_lock/unlock() to synchronize with
 *   the cpu-hotplug-callback call sites.
 *
 * We guarantee that only a single cpu is being
 * updated at any particular moment of time.
 */
struct ucode_cpu_info           ucode_cpu_info[NR_CPUS];

/*
 * Those patch levels cannot be updated to newer ones and thus should be final.
 */
static u32 final_levels[] = {
        0x01000098,
        0x0100009f,
        0x010000af,
        0, /* T-101 terminator */
};

struct early_load_data early_data;

/*
 * Check the current patch level on this CPU.
 *
 * Returns:
 *  - true: if update should stop
 *  - false: otherwise
 */
static bool amd_check_current_patch_level(void)
{
        u32 lvl, dummy, i;
        u32 *levels;

        native_rdmsr(MSR_AMD64_PATCH_LEVEL, lvl, dummy);

        levels = final_levels;

        for (i = 0; levels[i]; i++) {
                if (lvl == levels[i])
                        return true;
        }
        return false;
}

static bool __init check_loader_disabled_bsp(void)
{
        static const char *__dis_opt_str = "dis_ucode_ldr";
        const char *cmdline = boot_command_line;
        const char *option  = __dis_opt_str;

        /*
         * CPUID(1).ECX[31]: reserved for hypervisor use. This is still not
         * completely accurate as xen pv guests don't see that CPUID bit set but
         * that's good enough as they don't land on the BSP path anyway.
         */
        if (native_cpuid_ecx(1) & BIT(31))
                return true;

        if (x86_cpuid_vendor() == X86_VENDOR_AMD) {
                if (amd_check_current_patch_level())
                        return true;
        }

        if (cmdline_find_option_bool(cmdline, option) <= 0)
                dis_ucode_ldr = false;

        return dis_ucode_ldr;
}

void __init load_ucode_bsp(void)
{
        unsigned int cpuid_1_eax;
        bool intel = true;

        if (!have_cpuid_p())
                return;

        cpuid_1_eax = native_cpuid_eax(1);

        switch (x86_cpuid_vendor()) {
        case X86_VENDOR_INTEL:
                if (x86_family(cpuid_1_eax) < 6)
                        return;
                break;

        case X86_VENDOR_AMD:
                if (x86_family(cpuid_1_eax) < 0x10)
                        return;
                intel = false;
                break;

        default:
                return;
        }

        if (check_loader_disabled_bsp())
                return;

        if (intel)
                load_ucode_intel_bsp(&early_data);
        else
                load_ucode_amd_bsp(&early_data, cpuid_1_eax);
}

void load_ucode_ap(void)
{
        unsigned int cpuid_1_eax;

        if (dis_ucode_ldr)
                return;

        cpuid_1_eax = native_cpuid_eax(1);

        switch (x86_cpuid_vendor()) {
        case X86_VENDOR_INTEL:
                if (x86_family(cpuid_1_eax) >= 6)
                        load_ucode_intel_ap();
                break;
        case X86_VENDOR_AMD:
                if (x86_family(cpuid_1_eax) >= 0x10)
                        load_ucode_amd_ap(cpuid_1_eax);
                break;
        default:
                break;
        }
}

struct cpio_data __init find_microcode_in_initrd(const char *path)
{
#ifdef CONFIG_BLK_DEV_INITRD
        unsigned long start = 0;
        size_t size;

#ifdef CONFIG_X86_32
        size = boot_params.hdr.ramdisk_size;
        /* Early load on BSP has a temporary mapping. */
        if (size)
                start = initrd_start_early;

#else /* CONFIG_X86_64 */
        size  = (unsigned long)boot_params.ext_ramdisk_size << 32;
        size |= boot_params.hdr.ramdisk_size;

        if (size) {
                start  = (unsigned long)boot_params.ext_ramdisk_image << 32;
                start |= boot_params.hdr.ramdisk_image;
                start += PAGE_OFFSET;
        }
#endif

        /*
         * Fixup the start address: after reserve_initrd() runs, initrd_start
         * has the virtual address of the beginning of the initrd. It also
         * possibly relocates the ramdisk. In either case, initrd_start contains
         * the updated address so use that instead.
         */
        if (initrd_start)
                start = initrd_start;

        return find_cpio_data(path, (void *)start, size, NULL);
#else /* !CONFIG_BLK_DEV_INITRD */
        return (struct cpio_data){ NULL, 0, "" };
#endif
}

static void reload_early_microcode(unsigned int cpu)
{
        int vendor, family;

        vendor = x86_cpuid_vendor();
        family = x86_cpuid_family();

        switch (vendor) {
        case X86_VENDOR_INTEL:
                if (family >= 6)
                        reload_ucode_intel();
                break;
        case X86_VENDOR_AMD:
                if (family >= 0x10)
                        reload_ucode_amd(cpu);
                break;
        default:
                break;
        }
}

/* fake device for request_firmware */
static struct platform_device   *microcode_pdev;

#ifdef CONFIG_MICROCODE_LATE_LOADING
/*
 * Late loading dance. Why the heavy-handed stomp_machine effort?
 *
 * - HT siblings must be idle and not execute other code while the other sibling
 *   is loading microcode in order to avoid any negative interactions caused by
 *   the loading.
 *
 * - In addition, microcode update on the cores must be serialized until this
 *   requirement can be relaxed in the future. Right now, this is conservative
 *   and good.
 */
enum sibling_ctrl {
        /* Spinwait with timeout */
        SCTRL_WAIT,
        /* Invoke the microcode_apply() callback */
        SCTRL_APPLY,
        /* Proceed without invoking the microcode_apply() callback */
        SCTRL_DONE,
};

struct microcode_ctrl {
        enum sibling_ctrl       ctrl;
        enum ucode_state        result;
        unsigned int            ctrl_cpu;
        bool                    nmi_enabled;
};

DEFINE_STATIC_KEY_FALSE(microcode_nmi_handler_enable);
static DEFINE_PER_CPU(struct microcode_ctrl, ucode_ctrl);
static atomic_t late_cpus_in, offline_in_nmi;
static unsigned int loops_per_usec;
static cpumask_t cpu_offline_mask;

static noinstr bool wait_for_cpus(atomic_t *cnt)
{
        unsigned int timeout, loops;

        WARN_ON_ONCE(raw_atomic_dec_return(cnt) < 0);

        for (timeout = 0; timeout < USEC_PER_SEC; timeout++) {
                if (!raw_atomic_read(cnt))
                        return true;

                for (loops = 0; loops < loops_per_usec; loops++)
                        cpu_relax();

                /* If invoked directly, tickle the NMI watchdog */
                if (!microcode_ops->use_nmi && !(timeout % USEC_PER_MSEC)) {
                        instrumentation_begin();
                        touch_nmi_watchdog();
                        instrumentation_end();
                }
        }
        /* Prevent the late comers from making progress and let them time out */
        raw_atomic_inc(cnt);
        return false;
}

static noinstr bool wait_for_ctrl(void)
{
        unsigned int timeout, loops;

        for (timeout = 0; timeout < USEC_PER_SEC; timeout++) {
                if (raw_cpu_read(ucode_ctrl.ctrl) != SCTRL_WAIT)
                        return true;

                for (loops = 0; loops < loops_per_usec; loops++)
                        cpu_relax();

                /* If invoked directly, tickle the NMI watchdog */
                if (!microcode_ops->use_nmi && !(timeout % USEC_PER_MSEC)) {
                        instrumentation_begin();
                        touch_nmi_watchdog();
                        instrumentation_end();
                }
        }
        return false;
}

/*
 * Protected against instrumentation up to the point where the primary
 * thread completed the update. See microcode_nmi_handler() for details.
 */
static noinstr bool load_secondary_wait(unsigned int ctrl_cpu)
{
        /* Initial rendezvous to ensure that all CPUs have arrived */
        if (!wait_for_cpus(&late_cpus_in)) {
                raw_cpu_write(ucode_ctrl.result, UCODE_TIMEOUT);
                return false;
        }

        /*
         * Wait for primary threads to complete. If one of them hangs due
         * to the update, there is no way out. This is non-recoverable
         * because the CPU might hold locks or resources and confuse the
         * scheduler, watchdogs etc. There is no way to safely evacuate the
         * machine.
         */
        if (wait_for_ctrl())
                return true;

        instrumentation_begin();
        panic("Microcode load: Primary CPU %d timed out\n", ctrl_cpu);
        instrumentation_end();
}

/*
 * Protected against instrumentation up to the point where the primary
 * thread completed the update. See microcode_nmi_handler() for details.
 */
static noinstr void load_secondary(unsigned int cpu)
{
        unsigned int ctrl_cpu = raw_cpu_read(ucode_ctrl.ctrl_cpu);
        enum ucode_state ret;

        if (!load_secondary_wait(ctrl_cpu)) {
                instrumentation_begin();
                pr_err_once("load: %d CPUs timed out\n",
                            atomic_read(&late_cpus_in) - 1);
                instrumentation_end();
                return;
        }

        /* Primary thread completed. Allow to invoke instrumentable code */
        instrumentation_begin();
        /*
         * If the primary succeeded then invoke the apply() callback,
         * otherwise copy the state from the primary thread.
         */
        if (this_cpu_read(ucode_ctrl.ctrl) == SCTRL_APPLY)
                ret = microcode_ops->apply_microcode(cpu);
        else
                ret = per_cpu(ucode_ctrl.result, ctrl_cpu);

        this_cpu_write(ucode_ctrl.result, ret);
        this_cpu_write(ucode_ctrl.ctrl, SCTRL_DONE);
        instrumentation_end();
}

static void __load_primary(unsigned int cpu)
{
        struct cpumask *secondaries = topology_sibling_cpumask(cpu);
        enum sibling_ctrl ctrl;
        enum ucode_state ret;
        unsigned int sibling;

        /* Initial rendezvous to ensure that all CPUs have arrived */
        if (!wait_for_cpus(&late_cpus_in)) {
                this_cpu_write(ucode_ctrl.result, UCODE_TIMEOUT);
                pr_err_once("load: %d CPUs timed out\n", atomic_read(&late_cpus_in) - 1);
                return;
        }

        ret = microcode_ops->apply_microcode(cpu);
        this_cpu_write(ucode_ctrl.result, ret);
        this_cpu_write(ucode_ctrl.ctrl, SCTRL_DONE);

        /*
         * If the update was successful, let the siblings run the apply()
         * callback. If not, tell them it's done. This also covers the
         * case where the CPU has uniform loading at package or system
         * scope implemented but does not advertise it.
         */
        if (ret == UCODE_UPDATED || ret == UCODE_OK)
                ctrl = SCTRL_APPLY;
        else
                ctrl = SCTRL_DONE;

        for_each_cpu(sibling, secondaries) {
                if (sibling != cpu)
                        per_cpu(ucode_ctrl.ctrl, sibling) = ctrl;
        }
}

static bool kick_offline_cpus(unsigned int nr_offl)
{
        unsigned int cpu, timeout;

        for_each_cpu(cpu, &cpu_offline_mask) {
                /* Enable the rendezvous handler and send NMI */
                per_cpu(ucode_ctrl.nmi_enabled, cpu) = true;
                apic_send_nmi_to_offline_cpu(cpu);
        }

        /* Wait for them to arrive */
        for (timeout = 0; timeout < (USEC_PER_SEC / 2); timeout++) {
                if (atomic_read(&offline_in_nmi) == nr_offl)
                        return true;
                udelay(1);
        }
        /* Let the others time out */
        return false;
}

static void release_offline_cpus(void)
{
        unsigned int cpu;

        for_each_cpu(cpu, &cpu_offline_mask)
                per_cpu(ucode_ctrl.ctrl, cpu) = SCTRL_DONE;
}

static void load_primary(unsigned int cpu)
{
        unsigned int nr_offl = cpumask_weight(&cpu_offline_mask);
        bool proceed = true;

        /* Kick soft-offlined SMT siblings if required */
        if (!cpu && nr_offl)
                proceed = kick_offline_cpus(nr_offl);

        /* If the soft-offlined CPUs did not respond, abort */
        if (proceed)
                __load_primary(cpu);

        /* Unconditionally release soft-offlined SMT siblings if required */
        if (!cpu && nr_offl)
                release_offline_cpus();
}

/*
 * Minimal stub rendezvous handler for soft-offlined CPUs which participate
 * in the NMI rendezvous to protect against a concurrent NMI on affected
 * CPUs.
 */
void noinstr microcode_offline_nmi_handler(void)
{
        if (!raw_cpu_read(ucode_ctrl.nmi_enabled))
                return;
        raw_cpu_write(ucode_ctrl.nmi_enabled, false);
        raw_cpu_write(ucode_ctrl.result, UCODE_OFFLINE);
        raw_atomic_inc(&offline_in_nmi);
        wait_for_ctrl();
}

static noinstr bool microcode_update_handler(void)
{
        unsigned int cpu = raw_smp_processor_id();

        if (raw_cpu_read(ucode_ctrl.ctrl_cpu) == cpu) {
                instrumentation_begin();
                load_primary(cpu);
                instrumentation_end();
        } else {
                load_secondary(cpu);
        }

        instrumentation_begin();
        touch_nmi_watchdog();
        instrumentation_end();

        return true;
}

/*
 * Protection against instrumentation is required for CPUs which are not
 * safe against an NMI which is delivered to the secondary SMT sibling
 * while the primary thread updates the microcode. Instrumentation can end
 * up in #INT3, #DB and #PF. The IRET from those exceptions reenables NMI
 * which is the opposite of what the NMI rendezvous is trying to achieve.
 *
 * The primary thread is safe versus instrumentation as the actual
 * microcode update handles this correctly. It's only the sibling code
 * path which must be NMI safe until the primary thread completed the
 * update.
 */
bool noinstr microcode_nmi_handler(void)
{
        if (!raw_cpu_read(ucode_ctrl.nmi_enabled))
                return false;

        raw_cpu_write(ucode_ctrl.nmi_enabled, false);
        return microcode_update_handler();
}

static int load_cpus_stopped(void *unused)
{
        if (microcode_ops->use_nmi) {
                /* Enable the NMI handler and raise NMI */
                this_cpu_write(ucode_ctrl.nmi_enabled, true);
                apic->send_IPI(smp_processor_id(), NMI_VECTOR);
        } else {
                /* Just invoke the handler directly */
                microcode_update_handler();
        }
        return 0;
}

static int load_late_stop_cpus(bool is_safe)
{
        unsigned int cpu, updated = 0, failed = 0, timedout = 0, siblings = 0;
        unsigned int nr_offl, offline = 0;
        int old_rev = boot_cpu_data.microcode;
        struct cpuinfo_x86 prev_info;

        if (!is_safe) {
                pr_err("Late microcode loading without minimal revision check.\n");
                pr_err("You should switch to early loading, if possible.\n");
        }

        atomic_set(&late_cpus_in, num_online_cpus());
        atomic_set(&offline_in_nmi, 0);
        loops_per_usec = loops_per_jiffy / (TICK_NSEC / 1000);

        /*
         * Take a snapshot before the microcode update in order to compare and
         * check whether any bits changed after an update.
         */
        store_cpu_caps(&prev_info);

        if (microcode_ops->use_nmi)
                static_branch_enable_cpuslocked(&microcode_nmi_handler_enable);

        stop_machine_cpuslocked(load_cpus_stopped, NULL, cpu_online_mask);

        if (microcode_ops->use_nmi)
                static_branch_disable_cpuslocked(&microcode_nmi_handler_enable);

        /* Analyze the results */
        for_each_cpu_and(cpu, cpu_present_mask, &cpus_booted_once_mask) {
                switch (per_cpu(ucode_ctrl.result, cpu)) {
                case UCODE_UPDATED:     updated++; break;
                case UCODE_TIMEOUT:     timedout++; break;
                case UCODE_OK:          siblings++; break;
                case UCODE_OFFLINE:     offline++; break;
                default:                failed++; break;
                }
        }

        if (microcode_ops->finalize_late_load)
                microcode_ops->finalize_late_load(!updated);

        if (!updated) {
                /* Nothing changed. */
                if (!failed && !timedout)
                        return 0;

                nr_offl = cpumask_weight(&cpu_offline_mask);
                if (offline < nr_offl) {
                        pr_warn("%u offline siblings did not respond.\n",
                                nr_offl - atomic_read(&offline_in_nmi));
                        return -EIO;
                }
                pr_err("update failed: %u CPUs failed %u CPUs timed out\n",
                       failed, timedout);
                return -EIO;
        }

        if (!is_safe || failed || timedout)
                add_taint(TAINT_CPU_OUT_OF_SPEC, LOCKDEP_STILL_OK);

        pr_info("load: updated on %u primary CPUs with %u siblings\n", updated, siblings);
        if (failed || timedout) {
                pr_err("load incomplete. %u CPUs timed out or failed\n",
                       num_online_cpus() - (updated + siblings));
        }
        pr_info("revision: 0x%x -> 0x%x\n", old_rev, boot_cpu_data.microcode);
        microcode_check(&prev_info);

        return updated + siblings == num_online_cpus() ? 0 : -EIO;
}

/*
 * This function does two things:
 *
 * 1) Ensure that all required CPUs which are present and have been booted
 *    once are online.
 *
 *    To pass this check, all primary threads must be online.
 *
 *    If the microcode load is not safe against NMI then all SMT threads
 *    must be online as well because they still react to NMIs when they are
 *    soft-offlined and parked in one of the play_dead() variants. So if a
 *    NMI hits while the primary thread updates the microcode the resulting
 *    behaviour is undefined. The default play_dead() implementation on
 *    modern CPUs uses MWAIT, which is also not guaranteed to be safe
 *    against a microcode update which affects MWAIT.
 *
 *    As soft-offlined CPUs still react on NMIs, the SMT sibling
 *    restriction can be lifted when the vendor driver signals to use NMI
 *    for rendezvous and the APIC provides a mechanism to send an NMI to a
 *    soft-offlined CPU. The soft-offlined CPUs are then able to
 *    participate in the rendezvous in a trivial stub handler.
 *
 * 2) Initialize the per CPU control structure and create a cpumask
 *    which contains "offline"; secondary threads, so they can be handled
 *    correctly by a control CPU.
 */
static bool setup_cpus(void)
{
        struct microcode_ctrl ctrl = { .ctrl = SCTRL_WAIT, .result = -1, };
        bool allow_smt_offline;
        unsigned int cpu;

        allow_smt_offline = microcode_ops->nmi_safe ||
                (microcode_ops->use_nmi && apic->nmi_to_offline_cpu);

        cpumask_clear(&cpu_offline_mask);

        for_each_cpu_and(cpu, cpu_present_mask, &cpus_booted_once_mask) {
                /*
                 * Offline CPUs sit in one of the play_dead() functions
                 * with interrupts disabled, but they still react on NMIs
                 * and execute arbitrary code. Also MWAIT being updated
                 * while the offline CPU sits there is not necessarily safe
                 * on all CPU variants.
                 *
                 * Mark them in the offline_cpus mask which will be handled
                 * by CPU0 later in the update process.
                 *
                 * Ensure that the primary thread is online so that it is
                 * guaranteed that all cores are updated.
                 */
                if (!cpu_online(cpu)) {
                        if (topology_is_primary_thread(cpu) || !allow_smt_offline) {
                                pr_err("CPU %u not online, loading aborted\n", cpu);
                                return false;
                        }
                        cpumask_set_cpu(cpu, &cpu_offline_mask);
                        per_cpu(ucode_ctrl, cpu) = ctrl;
                        continue;
                }

                /*
                 * Initialize the per CPU state. This is core scope for now,
                 * but prepared to take package or system scope into account.
                 */
                ctrl.ctrl_cpu = cpumask_first(topology_sibling_cpumask(cpu));
                per_cpu(ucode_ctrl, cpu) = ctrl;
        }
        return true;
}

static int load_late_locked(void)
{
        if (!setup_cpus())
                return -EBUSY;

        switch (microcode_ops->request_microcode_fw(0, &microcode_pdev->dev)) {
        case UCODE_NEW:
                return load_late_stop_cpus(false);
        case UCODE_NEW_SAFE:
                return load_late_stop_cpus(true);
        case UCODE_NFOUND:
                return -ENOENT;
        default:
                return -EBADFD;
        }
}

static ssize_t reload_store(struct device *dev,
                            struct device_attribute *attr,
                            const char *buf, size_t size)
{
        unsigned long val;
        ssize_t ret;

        ret = kstrtoul(buf, 0, &val);
        if (ret || val != 1)
                return -EINVAL;

        cpus_read_lock();
        ret = load_late_locked();
        cpus_read_unlock();

        return ret ? : size;
}

static DEVICE_ATTR_WO(reload);
#endif

static ssize_t version_show(struct device *dev,
                        struct device_attribute *attr, char *buf)
{
        struct ucode_cpu_info *uci = ucode_cpu_info + dev->id;

        return sprintf(buf, "0x%x\n", uci->cpu_sig.rev);
}

static ssize_t processor_flags_show(struct device *dev,
                        struct device_attribute *attr, char *buf)
{
        struct ucode_cpu_info *uci = ucode_cpu_info + dev->id;

        return sprintf(buf, "0x%x\n", uci->cpu_sig.pf);
}

static DEVICE_ATTR_RO(version);
static DEVICE_ATTR_RO(processor_flags);

static struct attribute *mc_default_attrs[] = {
        &dev_attr_version.attr,
        &dev_attr_processor_flags.attr,
        NULL
};

static const struct attribute_group mc_attr_group = {
        .attrs                  = mc_default_attrs,
        .name                   = "microcode",
};

static void microcode_fini_cpu(int cpu)
{
        if (microcode_ops->microcode_fini_cpu)
                microcode_ops->microcode_fini_cpu(cpu);
}

/**
 * microcode_bsp_resume - Update boot CPU microcode during resume.
 */
void microcode_bsp_resume(void)
{
        int cpu = smp_processor_id();
        struct ucode_cpu_info *uci = ucode_cpu_info + cpu;

        if (uci->mc)
                microcode_ops->apply_microcode(cpu);
        else
                reload_early_microcode(cpu);
}

static struct syscore_ops mc_syscore_ops = {
        .resume = microcode_bsp_resume,
};

static int mc_cpu_online(unsigned int cpu)
{
        struct ucode_cpu_info *uci = ucode_cpu_info + cpu;
        struct device *dev = get_cpu_device(cpu);

        memset(uci, 0, sizeof(*uci));

        microcode_ops->collect_cpu_info(cpu, &uci->cpu_sig);
        cpu_data(cpu).microcode = uci->cpu_sig.rev;
        if (!cpu)
                boot_cpu_data.microcode = uci->cpu_sig.rev;

        if (sysfs_create_group(&dev->kobj, &mc_attr_group))
                pr_err("Failed to create group for CPU%d\n", cpu);
        return 0;
}

static int mc_cpu_down_prep(unsigned int cpu)
{
        struct device *dev = get_cpu_device(cpu);

        microcode_fini_cpu(cpu);
        sysfs_remove_group(&dev->kobj, &mc_attr_group);
        return 0;
}

static struct attribute *cpu_root_microcode_attrs[] = {
#ifdef CONFIG_MICROCODE_LATE_LOADING
        &dev_attr_reload.attr,
#endif
        NULL
};

static const struct attribute_group cpu_root_microcode_group = {
        .name  = "microcode",
        .attrs = cpu_root_microcode_attrs,
};

static int __init microcode_init(void)
{
        struct device *dev_root;
        struct cpuinfo_x86 *c = &boot_cpu_data;
        int error;

        if (dis_ucode_ldr)
                return -EINVAL;

        if (c->x86_vendor == X86_VENDOR_INTEL)
                microcode_ops = init_intel_microcode();
        else if (c->x86_vendor == X86_VENDOR_AMD)
                microcode_ops = init_amd_microcode();
        else
                pr_err("no support for this CPU vendor\n");

        if (!microcode_ops)
                return -ENODEV;

        pr_info_once("Current revision: 0x%08x\n", (early_data.new_rev ?: early_data.old_rev));

        if (early_data.new_rev)
                pr_info_once("Updated early from: 0x%08x\n", early_data.old_rev);

        microcode_pdev = platform_device_register_simple("microcode", -1, NULL, 0);
        if (IS_ERR(microcode_pdev))
                return PTR_ERR(microcode_pdev);

        dev_root = bus_get_dev_root(&cpu_subsys);
        if (dev_root) {
                error = sysfs_create_group(&dev_root->kobj, &cpu_root_microcode_group);
                put_device(dev_root);
                if (error) {
                        pr_err("Error creating microcode group!\n");
                        goto out_pdev;
                }
        }

        register_syscore_ops(&mc_syscore_ops);
        cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/microcode:online",
                          mc_cpu_online, mc_cpu_down_prep);

        return 0;

 out_pdev:
        platform_device_unregister(microcode_pdev);
        return error;

}
late_initcall(microcode_init);