/* * (c) 2005-2016 Advanced Micro Devices, Inc. * Your use of this code is subject to the terms and conditions of the * GNU general public license version 2. See "COPYING" or * http://www.gnu.org/licenses/gpl.html * * Written by Jacob Shin - AMD, Inc. * Maintained by: Borislav Petkov * * All MC4_MISCi registers are shared between cores on a node. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #define NR_BLOCKS 5 #define THRESHOLD_MAX 0xFFF #define INT_TYPE_APIC 0x00020000 #define MASK_VALID_HI 0x80000000 #define MASK_CNTP_HI 0x40000000 #define MASK_LOCKED_HI 0x20000000 #define MASK_LVTOFF_HI 0x00F00000 #define MASK_COUNT_EN_HI 0x00080000 #define MASK_INT_TYPE_HI 0x00060000 #define MASK_OVERFLOW_HI 0x00010000 #define MASK_ERR_COUNT_HI 0x00000FFF #define MASK_BLKPTR_LO 0xFF000000 #define MCG_XBLK_ADDR 0xC0000400 /* Deferred error settings */ #define MSR_CU_DEF_ERR 0xC0000410 #define MASK_DEF_LVTOFF 0x000000F0 #define MASK_DEF_INT_TYPE 0x00000006 #define DEF_LVT_OFF 0x2 #define DEF_INT_TYPE_APIC 0x2 /* Scalable MCA: */ /* Threshold LVT offset is at MSR0xC0000410[15:12] */ #define SMCA_THR_LVT_OFF 0xF000 /* * OS is required to set the MCAX bit to acknowledge that it is now using the * new MSR ranges and new registers under each bank. It also means that the OS * will configure deferred errors in the new MCx_CONFIG register. If the bit is * not set, uncorrectable errors will cause a system panic. */ #define SMCA_MCAX_EN_OFF 0x1 static const char * const th_names[] = { "load_store", "insn_fetch", "combined_unit", "", "northbridge", "execution_unit", }; /* Define HWID to IP type mappings for Scalable MCA */ struct amd_hwid amd_hwids[] = { [SMCA_F17H_CORE] = { "f17h_core", 0xB0 }, [SMCA_DF] = { "data_fabric", 0x2E }, [SMCA_UMC] = { "umc", 0x96 }, [SMCA_PB] = { "param_block", 0x5 }, [SMCA_PSP] = { "psp", 0xFF }, [SMCA_SMU] = { "smu", 0x1 }, }; EXPORT_SYMBOL_GPL(amd_hwids); const char * const amd_core_mcablock_names[] = { [SMCA_LS] = "load_store", [SMCA_IF] = "insn_fetch", [SMCA_L2_CACHE] = "l2_cache", [SMCA_DE] = "decode_unit", [RES] = "", [SMCA_EX] = "execution_unit", [SMCA_FP] = "floating_point", [SMCA_L3_CACHE] = "l3_cache", }; EXPORT_SYMBOL_GPL(amd_core_mcablock_names); const char * const amd_df_mcablock_names[] = { [SMCA_CS] = "coherent_slave", [SMCA_PIE] = "pie", }; EXPORT_SYMBOL_GPL(amd_df_mcablock_names); static DEFINE_PER_CPU(struct threshold_bank **, threshold_banks); static DEFINE_PER_CPU(unsigned char, bank_map); /* see which banks are on */ static void amd_threshold_interrupt(void); static void amd_deferred_error_interrupt(void); static void default_deferred_error_interrupt(void) { pr_err("Unexpected deferred interrupt at vector %x\n", DEFERRED_ERROR_VECTOR); } void (*deferred_error_int_vector)(void) = default_deferred_error_interrupt; /* * CPU Initialization */ struct thresh_restart { struct threshold_block *b; int reset; int set_lvt_off; int lvt_off; u16 old_limit; }; static inline bool is_shared_bank(int bank) { /* * Scalable MCA provides for only one core to have access to the MSRs of * a shared bank. */ if (mce_flags.smca) return false; /* Bank 4 is for northbridge reporting and is thus shared */ return (bank == 4); } static const char *bank4_names(const struct threshold_block *b) { switch (b->address) { /* MSR4_MISC0 */ case 0x00000413: return "dram"; case 0xc0000408: return "ht_links"; case 0xc0000409: return "l3_cache"; default: WARN(1, "Funny MSR: 0x%08x\n", b->address); return ""; } }; static bool lvt_interrupt_supported(unsigned int bank, u32 msr_high_bits) { /* * bank 4 supports APIC LVT interrupts implicitly since forever. */ if (bank == 4) return true; /* * IntP: interrupt present; if this bit is set, the thresholding * bank can generate APIC LVT interrupts */ return msr_high_bits & BIT(28); } static int lvt_off_valid(struct threshold_block *b, int apic, u32 lo, u32 hi) { int msr = (hi & MASK_LVTOFF_HI) >> 20; if (apic < 0) { pr_err(FW_BUG "cpu %d, failed to setup threshold interrupt " "for bank %d, block %d (MSR%08X=0x%x%08x)\n", b->cpu, b->bank, b->block, b->address, hi, lo); return 0; } if (apic != msr) { /* * On SMCA CPUs, LVT offset is programmed at a different MSR, and * the BIOS provides the value. The original field where LVT offset * was set is reserved. Return early here: */ if (mce_flags.smca) return 0; pr_err(FW_BUG "cpu %d, invalid threshold interrupt offset %d " "for bank %d, block %d (MSR%08X=0x%x%08x)\n", b->cpu, apic, b->bank, b->block, b->address, hi, lo); return 0; } return 1; }; /* Reprogram MCx_MISC MSR behind this threshold bank. */ static void threshold_restart_bank(void *_tr) { struct thresh_restart *tr = _tr; u32 hi, lo; rdmsr(tr->b->address, lo, hi); if (tr->b->threshold_limit < (hi & THRESHOLD_MAX)) tr->reset = 1; /* limit cannot be lower than err count */ if (tr->reset) { /* reset err count and overflow bit */ hi = (hi & ~(MASK_ERR_COUNT_HI | MASK_OVERFLOW_HI)) | (THRESHOLD_MAX - tr->b->threshold_limit); } else if (tr->old_limit) { /* change limit w/o reset */ int new_count = (hi & THRESHOLD_MAX) + (tr->old_limit - tr->b->threshold_limit); hi = (hi & ~MASK_ERR_COUNT_HI) | (new_count & THRESHOLD_MAX); } /* clear IntType */ hi &= ~MASK_INT_TYPE_HI; if (!tr->b->interrupt_capable) goto done; if (tr->set_lvt_off) { if (lvt_off_valid(tr->b, tr->lvt_off, lo, hi)) { /* set new lvt offset */ hi &= ~MASK_LVTOFF_HI; hi |= tr->lvt_off << 20; } } if (tr->b->interrupt_enable) hi |= INT_TYPE_APIC; done: hi |= MASK_COUNT_EN_HI; wrmsr(tr->b->address, lo, hi); } static void mce_threshold_block_init(struct threshold_block *b, int offset) { struct thresh_restart tr = { .b = b, .set_lvt_off = 1, .lvt_off = offset, }; b->threshold_limit = THRESHOLD_MAX; threshold_restart_bank(&tr); }; static int setup_APIC_mce_threshold(int reserved, int new) { if (reserved < 0 && !setup_APIC_eilvt(new, THRESHOLD_APIC_VECTOR, APIC_EILVT_MSG_FIX, 0)) return new; return reserved; } static int setup_APIC_deferred_error(int reserved, int new) { if (reserved < 0 && !setup_APIC_eilvt(new, DEFERRED_ERROR_VECTOR, APIC_EILVT_MSG_FIX, 0)) return new; return reserved; } static void deferred_error_interrupt_enable(struct cpuinfo_x86 *c) { u32 low = 0, high = 0; int def_offset = -1, def_new; if (rdmsr_safe(MSR_CU_DEF_ERR, &low, &high)) return; def_new = (low & MASK_DEF_LVTOFF) >> 4; if (!(low & MASK_DEF_LVTOFF)) { pr_err(FW_BUG "Your BIOS is not setting up LVT offset 0x2 for deferred error IRQs correctly.\n"); def_new = DEF_LVT_OFF; low = (low & ~MASK_DEF_LVTOFF) | (DEF_LVT_OFF << 4); } def_offset = setup_APIC_deferred_error(def_offset, def_new); if ((def_offset == def_new) && (deferred_error_int_vector != amd_deferred_error_interrupt)) deferred_error_int_vector = amd_deferred_error_interrupt; low = (low & ~MASK_DEF_INT_TYPE) | DEF_INT_TYPE_APIC; wrmsr(MSR_CU_DEF_ERR, low, high); } static u32 get_block_address(u32 current_addr, u32 low, u32 high, unsigned int bank, unsigned int block) { u32 addr = 0, offset = 0; if (mce_flags.smca) { if (!block) { addr = MSR_AMD64_SMCA_MCx_MISC(bank); } else { /* * For SMCA enabled processors, BLKPTR field of the * first MISC register (MCx_MISC0) indicates presence of * additional MISC register set (MISC1-4). */ u32 low, high; if (rdmsr_safe(MSR_AMD64_SMCA_MCx_CONFIG(bank), &low, &high)) return addr; if (!(low & MCI_CONFIG_MCAX)) return addr; if (!rdmsr_safe(MSR_AMD64_SMCA_MCx_MISC(bank), &low, &high) && (low & MASK_BLKPTR_LO)) addr = MSR_AMD64_SMCA_MCx_MISCy(bank, block - 1); } return addr; } /* Fall back to method we used for older processors: */ switch (block) { case 0: addr = MSR_IA32_MCx_MISC(bank); break; case 1: offset = ((low & MASK_BLKPTR_LO) >> 21); if (offset) addr = MCG_XBLK_ADDR + offset; break; default: addr = ++current_addr; } return addr; } static int prepare_threshold_block(unsigned int bank, unsigned int block, u32 addr, int offset, u32 misc_high) { unsigned int cpu = smp_processor_id(); struct threshold_block b; int new; if (!block) per_cpu(bank_map, cpu) |= (1 << bank); memset(&b, 0, sizeof(b)); b.cpu = cpu; b.bank = bank; b.block = block; b.address = addr; b.interrupt_capable = lvt_interrupt_supported(bank, misc_high); if (!b.interrupt_capable) goto done; b.interrupt_enable = 1; if (mce_flags.smca) { u32 smca_low, smca_high; u32 smca_addr = MSR_AMD64_SMCA_MCx_CONFIG(bank); if (!rdmsr_safe(smca_addr, &smca_low, &smca_high)) { smca_high |= SMCA_MCAX_EN_OFF; wrmsr(smca_addr, smca_low, smca_high); } /* Gather LVT offset for thresholding: */ if (rdmsr_safe(MSR_CU_DEF_ERR, &smca_low, &smca_high)) goto out; new = (smca_low & SMCA_THR_LVT_OFF) >> 12; } else { new = (misc_high & MASK_LVTOFF_HI) >> 20; } offset = setup_APIC_mce_threshold(offset, new); if ((offset == new) && (mce_threshold_vector != amd_threshold_interrupt)) mce_threshold_vector = amd_threshold_interrupt; done: mce_threshold_block_init(&b, offset); out: return offset; } /* cpu init entry point, called from mce.c with preempt off */ void mce_amd_feature_init(struct cpuinfo_x86 *c) { u32 low = 0, high = 0, address = 0; unsigned int bank, block; int offset = -1; for (bank = 0; bank < mca_cfg.banks; ++bank) { for (block = 0; block < NR_BLOCKS; ++block) { address = get_block_address(address, low, high, bank, block); if (!address) break; if (rdmsr_safe(address, &low, &high)) break; if (!(high & MASK_VALID_HI)) continue; if (!(high & MASK_CNTP_HI) || (high & MASK_LOCKED_HI)) continue; offset = prepare_threshold_block(bank, block, address, offset, high); } } if (mce_flags.succor) deferred_error_interrupt_enable(c); } static void __log_error(unsigned int bank, bool threshold_err, u64 misc) { struct mce m; u64 status; rdmsrl(MSR_IA32_MCx_STATUS(bank), status); if (!(status & MCI_STATUS_VAL)) return; mce_setup(&m); m.status = status; m.bank = bank; if (threshold_err) m.misc = misc; if (m.status & MCI_STATUS_ADDRV) rdmsrl(MSR_IA32_MCx_ADDR(bank), m.addr); mce_log(&m); wrmsrl(MSR_IA32_MCx_STATUS(bank), 0); } static inline void __smp_deferred_error_interrupt(void) { inc_irq_stat(irq_deferred_error_count); deferred_error_int_vector(); } asmlinkage __visible void smp_deferred_error_interrupt(void) { entering_irq(); __smp_deferred_error_interrupt(); exiting_ack_irq(); } asmlinkage __visible void smp_trace_deferred_error_interrupt(void) { entering_irq(); trace_deferred_error_apic_entry(DEFERRED_ERROR_VECTOR); __smp_deferred_error_interrupt(); trace_deferred_error_apic_exit(DEFERRED_ERROR_VECTOR); exiting_ack_irq(); } /* APIC interrupt handler for deferred errors */ static void amd_deferred_error_interrupt(void) { u64 status; unsigned int bank; for (bank = 0; bank < mca_cfg.banks; ++bank) { rdmsrl(MSR_IA32_MCx_STATUS(bank), status); if (!(status & MCI_STATUS_VAL) || !(status & MCI_STATUS_DEFERRED)) continue; __log_error(bank, false, 0); break; } } /* * APIC Interrupt Handler */ /* * threshold interrupt handler will service THRESHOLD_APIC_VECTOR. * the interrupt goes off when error_count reaches threshold_limit. * the handler will simply log mcelog w/ software defined bank number. */ static void amd_threshold_interrupt(void) { u32 low = 0, high = 0, address = 0; int cpu = smp_processor_id(); unsigned int bank, block; /* assume first bank caused it */ for (bank = 0; bank < mca_cfg.banks; ++bank) { if (!(per_cpu(bank_map, cpu) & (1 << bank))) continue; for (block = 0; block < NR_BLOCKS; ++block) { address = get_block_address(address, low, high, bank, block); if (!address) break; if (rdmsr_safe(address, &low, &high)) break; if (!(high & MASK_VALID_HI)) { if (block) continue; else break; } if (!(high & MASK_CNTP_HI) || (high & MASK_LOCKED_HI)) continue; /* * Log the machine check that caused the threshold * event. */ if (high & MASK_OVERFLOW_HI) goto log; } } return; log: __log_error(bank, true, ((u64)high << 32) | low); } /* * Sysfs Interface */ struct threshold_attr { struct attribute attr; ssize_t (*show) (struct threshold_block *, char *); ssize_t (*store) (struct threshold_block *, const char *, size_t count); }; #define SHOW_FIELDS(name) \ static ssize_t show_ ## name(struct threshold_block *b, char *buf) \ { \ return sprintf(buf, "%lu\n", (unsigned long) b->name); \ } SHOW_FIELDS(interrupt_enable) SHOW_FIELDS(threshold_limit) static ssize_t store_interrupt_enable(struct threshold_block *b, const char *buf, size_t size) { struct thresh_restart tr; unsigned long new; if (!b->interrupt_capable) return -EINVAL; if (kstrtoul(buf, 0, &new) < 0) return -EINVAL; b->interrupt_enable = !!new; memset(&tr, 0, sizeof(tr)); tr.b = b; smp_call_function_single(b->cpu, threshold_restart_bank, &tr, 1); return size; } static ssize_t store_threshold_limit(struct threshold_block *b, const char *buf, size_t size) { struct thresh_restart tr; unsigned long new; if (kstrtoul(buf, 0, &new) < 0) return -EINVAL; if (new > THRESHOLD_MAX) new = THRESHOLD_MAX; if (new < 1) new = 1; memset(&tr, 0, sizeof(tr)); tr.old_limit = b->threshold_limit; b->threshold_limit = new; tr.b = b; smp_call_function_single(b->cpu, threshold_restart_bank, &tr, 1); return size; } static ssize_t show_error_count(struct threshold_block *b, char *buf) { u32 lo, hi; rdmsr_on_cpu(b->cpu, b->address, &lo, &hi); return sprintf(buf, "%u\n", ((hi & THRESHOLD_MAX) - (THRESHOLD_MAX - b->threshold_limit))); } static struct threshold_attr error_count = { .attr = {.name = __stringify(error_count), .mode = 0444 }, .show = show_error_count, }; #define RW_ATTR(val) \ static struct threshold_attr val = { \ .attr = {.name = __stringify(val), .mode = 0644 }, \ .show = show_## val, \ .store = store_## val, \ }; RW_ATTR(interrupt_enable); RW_ATTR(threshold_limit); static struct attribute *default_attrs[] = { &threshold_limit.attr, &error_count.attr, NULL, /* possibly interrupt_enable if supported, see below */ NULL, }; #define to_block(k) container_of(k, struct threshold_block, kobj) #define to_attr(a) container_of(a, struct threshold_attr, attr) static ssize_t show(struct kobject *kobj, struct attribute *attr, char *buf) { struct threshold_block *b = to_block(kobj); struct threshold_attr *a = to_attr(attr); ssize_t ret; ret = a->show ? a->show(b, buf) : -EIO; return ret; } static ssize_t store(struct kobject *kobj, struct attribute *attr, const char *buf, size_t count) { struct threshold_block *b = to_block(kobj); struct threshold_attr *a = to_attr(attr); ssize_t ret; ret = a->store ? a->store(b, buf, count) : -EIO; return ret; } static const struct sysfs_ops threshold_ops = { .show = show, .store = store, }; static struct kobj_type threshold_ktype = { .sysfs_ops = &threshold_ops, .default_attrs = default_attrs, }; static int allocate_threshold_blocks(unsigned int cpu, unsigned int bank, unsigned int block, u32 address) { struct threshold_block *b = NULL; u32 low, high; int err; if ((bank >= mca_cfg.banks) || (block >= NR_BLOCKS)) return 0; if (rdmsr_safe_on_cpu(cpu, address, &low, &high)) return 0; if (!(high & MASK_VALID_HI)) { if (block) goto recurse; else return 0; } if (!(high & MASK_CNTP_HI) || (high & MASK_LOCKED_HI)) goto recurse; b = kzalloc(sizeof(struct threshold_block), GFP_KERNEL); if (!b) return -ENOMEM; b->block = block; b->bank = bank; b->cpu = cpu; b->address = address; b->interrupt_enable = 0; b->interrupt_capable = lvt_interrupt_supported(bank, high); b->threshold_limit = THRESHOLD_MAX; if (b->interrupt_capable) { threshold_ktype.default_attrs[2] = &interrupt_enable.attr; b->interrupt_enable = 1; } else { threshold_ktype.default_attrs[2] = NULL; } INIT_LIST_HEAD(&b->miscj); if (per_cpu(threshold_banks, cpu)[bank]->blocks) { list_add(&b->miscj, &per_cpu(threshold_banks, cpu)[bank]->blocks->miscj); } else { per_cpu(threshold_banks, cpu)[bank]->blocks = b; } err = kobject_init_and_add(&b->kobj, &threshold_ktype, per_cpu(threshold_banks, cpu)[bank]->kobj, (bank == 4 ? bank4_names(b) : th_names[bank])); if (err) goto out_free; recurse: address = get_block_address(address, low, high, bank, ++block); if (!address) return 0; err = allocate_threshold_blocks(cpu, bank, block, address); if (err) goto out_free; if (b) kobject_uevent(&b->kobj, KOBJ_ADD); return err; out_free: if (b) { kobject_put(&b->kobj); list_del(&b->miscj); kfree(b); } return err; } static int __threshold_add_blocks(struct threshold_bank *b) { struct list_head *head = &b->blocks->miscj; struct threshold_block *pos = NULL; struct threshold_block *tmp = NULL; int err = 0; err = kobject_add(&b->blocks->kobj, b->kobj, b->blocks->kobj.name); if (err) return err; list_for_each_entry_safe(pos, tmp, head, miscj) { err = kobject_add(&pos->kobj, b->kobj, pos->kobj.name); if (err) { list_for_each_entry_safe_reverse(pos, tmp, head, miscj) kobject_del(&pos->kobj); return err; } } return err; } static int threshold_create_bank(unsigned int cpu, unsigned int bank) { struct device *dev = per_cpu(mce_device, cpu); struct amd_northbridge *nb = NULL; struct threshold_bank *b = NULL; const char *name = th_names[bank]; int err = 0; if (is_shared_bank(bank)) { nb = node_to_amd_nb(amd_get_nb_id(cpu)); /* threshold descriptor already initialized on this node? */ if (nb && nb->bank4) { /* yes, use it */ b = nb->bank4; err = kobject_add(b->kobj, &dev->kobj, name); if (err) goto out; per_cpu(threshold_banks, cpu)[bank] = b; atomic_inc(&b->cpus); err = __threshold_add_blocks(b); goto out; } } b = kzalloc(sizeof(struct threshold_bank), GFP_KERNEL); if (!b) { err = -ENOMEM; goto out; } b->kobj = kobject_create_and_add(name, &dev->kobj); if (!b->kobj) { err = -EINVAL; goto out_free; } per_cpu(threshold_banks, cpu)[bank] = b; if (is_shared_bank(bank)) { atomic_set(&b->cpus, 1); /* nb is already initialized, see above */ if (nb) { WARN_ON(nb->bank4); nb->bank4 = b; } } err = allocate_threshold_blocks(cpu, bank, 0, MSR_IA32_MCx_MISC(bank)); if (!err) goto out; out_free: kfree(b); out: return err; } /* create dir/files for all valid threshold banks */ static int threshold_create_device(unsigned int cpu) { unsigned int bank; struct threshold_bank **bp; int err = 0; bp = kzalloc(sizeof(struct threshold_bank *) * mca_cfg.banks, GFP_KERNEL); if (!bp) return -ENOMEM; per_cpu(threshold_banks, cpu) = bp; for (bank = 0; bank < mca_cfg.banks; ++bank) { if (!(per_cpu(bank_map, cpu) & (1 << bank))) continue; err = threshold_create_bank(cpu, bank); if (err) return err; } return err; } static void deallocate_threshold_block(unsigned int cpu, unsigned int bank) { struct threshold_block *pos = NULL; struct threshold_block *tmp = NULL; struct threshold_bank *head = per_cpu(threshold_banks, cpu)[bank]; if (!head) return; list_for_each_entry_safe(pos, tmp, &head->blocks->miscj, miscj) { kobject_put(&pos->kobj); list_del(&pos->miscj); kfree(pos); } kfree(per_cpu(threshold_banks, cpu)[bank]->blocks); per_cpu(threshold_banks, cpu)[bank]->blocks = NULL; } static void __threshold_remove_blocks(struct threshold_bank *b) { struct threshold_block *pos = NULL; struct threshold_block *tmp = NULL; kobject_del(b->kobj); list_for_each_entry_safe(pos, tmp, &b->blocks->miscj, miscj) kobject_del(&pos->kobj); } static void threshold_remove_bank(unsigned int cpu, int bank) { struct amd_northbridge *nb; struct threshold_bank *b; b = per_cpu(threshold_banks, cpu)[bank]; if (!b) return; if (!b->blocks) goto free_out; if (is_shared_bank(bank)) { if (!atomic_dec_and_test(&b->cpus)) { __threshold_remove_blocks(b); per_cpu(threshold_banks, cpu)[bank] = NULL; return; } else { /* * the last CPU on this node using the shared bank is * going away, remove that bank now. */ nb = node_to_amd_nb(amd_get_nb_id(cpu)); nb->bank4 = NULL; } } deallocate_threshold_block(cpu, bank); free_out: kobject_del(b->kobj); kobject_put(b->kobj); kfree(b); per_cpu(threshold_banks, cpu)[bank] = NULL; } static void threshold_remove_device(unsigned int cpu) { unsigned int bank; for (bank = 0; bank < mca_cfg.banks; ++bank) { if (!(per_cpu(bank_map, cpu) & (1 << bank))) continue; threshold_remove_bank(cpu, bank); } kfree(per_cpu(threshold_banks, cpu)); } /* get notified when a cpu comes on/off */ static void amd_64_threshold_cpu_callback(unsigned long action, unsigned int cpu) { switch (action) { case CPU_ONLINE: case CPU_ONLINE_FROZEN: threshold_create_device(cpu); break; case CPU_DEAD: case CPU_DEAD_FROZEN: threshold_remove_device(cpu); break; default: break; } } static __init int threshold_init_device(void) { unsigned lcpu = 0; /* to hit CPUs online before the notifier is up */ for_each_online_cpu(lcpu) { int err = threshold_create_device(lcpu); if (err) return err; } threshold_cpu_callback = amd_64_threshold_cpu_callback; return 0; } /* * there are 3 funcs which need to be _initcalled in a logic sequence: * 1. xen_late_init_mcelog * 2. mcheck_init_device * 3. threshold_init_device * * xen_late_init_mcelog must register xen_mce_chrdev_device before * native mce_chrdev_device registration if running under xen platform; * * mcheck_init_device should be inited before threshold_init_device to * initialize mce_device, otherwise a NULL ptr dereference will cause panic. * * so we use following _initcalls * 1. device_initcall(xen_late_init_mcelog); * 2. device_initcall_sync(mcheck_init_device); * 3. late_initcall(threshold_init_device); * * when running under xen, the initcall order is 1,2,3; * on baremetal, we skip 1 and we do only 2 and 3. */ late_initcall(threshold_init_device);