From cd9c57cad3fe89ea949b9266cddc947c0838f7af Mon Sep 17 00:00:00 2001 From: Borislav Petkov Date: Tue, 1 Nov 2016 12:52:27 +0100 Subject: [PATCH] x86/MCE: Dump MCE to dmesg if no consumers When there are no error record consumers registered with the kernel, the only thing that appears in dmesg is something like: [ 300.000326] mce: [Hardware Error]: Machine check events logged and the error records are gone. Which is seriously counterproductive. So let's dump them to dmesg instead, in such a case. Requested-by: Eric Morton Signed-off-by: Borislav Petkov Cc: Tony Luck Link: http://lkml.kernel.org/r/20161101120911.13163-4-bp@alien8.de Signed-off-by: Thomas Gleixner --- arch/x86/kernel/cpu/mcheck/mce.c | 52 ++++++++++++++++++++++++++++---- 1 file changed, 46 insertions(+), 6 deletions(-) diff --git a/arch/x86/kernel/cpu/mcheck/mce.c b/arch/x86/kernel/cpu/mcheck/mce.c index a7fdf453d895..4ca00474804b 100644 --- a/arch/x86/kernel/cpu/mcheck/mce.c +++ b/arch/x86/kernel/cpu/mcheck/mce.c @@ -207,8 +207,12 @@ EXPORT_SYMBOL_GPL(mce_inject_log); static struct notifier_block mce_srao_nb; +static atomic_t num_notifiers; + void mce_register_decode_chain(struct notifier_block *nb) { + atomic_inc(&num_notifiers); + /* Ensure SRAO notifier has the highest priority in the decode chain. */ if (nb != &mce_srao_nb && nb->priority == INT_MAX) nb->priority -= 1; @@ -219,6 +223,8 @@ EXPORT_SYMBOL_GPL(mce_register_decode_chain); void mce_unregister_decode_chain(struct notifier_block *nb) { + atomic_dec(&num_notifiers); + atomic_notifier_chain_unregister(&x86_mce_decoder_chain, nb); } EXPORT_SYMBOL_GPL(mce_unregister_decode_chain); @@ -270,17 +276,17 @@ struct mca_msr_regs msr_ops = { .misc = misc_reg }; -static void print_mce(struct mce *m) +static void __print_mce(struct mce *m) { - int ret = 0; - - pr_emerg(HW_ERR "CPU %d: Machine Check Exception: %Lx Bank %d: %016Lx\n", - m->extcpu, m->mcgstatus, m->bank, m->status); + pr_emerg(HW_ERR "CPU %d: Machine Check%s: %Lx Bank %d: %016Lx\n", + m->extcpu, + (m->mcgstatus & MCG_STATUS_MCIP ? " Exception" : ""), + m->mcgstatus, m->bank, m->status); if (m->ip) { pr_emerg(HW_ERR "RIP%s %02x:<%016Lx> ", !(m->mcgstatus & MCG_STATUS_EIPV) ? " !INEXACT!" : "", - m->cs, m->ip); + m->cs, m->ip); if (m->cs == __KERNEL_CS) print_symbol("{%s}", m->ip); @@ -308,6 +314,13 @@ static void print_mce(struct mce *m) pr_emerg(HW_ERR "PROCESSOR %u:%x TIME %llu SOCKET %u APIC %x microcode %x\n", m->cpuvendor, m->cpuid, m->time, m->socketid, m->apicid, cpu_data(m->extcpu).microcode); +} + +static void print_mce(struct mce *m) +{ + int ret = 0; + + __print_mce(m); /* * Print out human-readable details about the MCE error, @@ -569,6 +582,32 @@ static struct notifier_block mce_srao_nb = { .priority = INT_MAX, }; +static int mce_default_notifier(struct notifier_block *nb, unsigned long val, + void *data) +{ + struct mce *m = (struct mce *)data; + + if (!m) + return NOTIFY_DONE; + + /* + * Run the default notifier if we have only the SRAO + * notifier and us registered. + */ + if (atomic_read(&num_notifiers) > 2) + return NOTIFY_DONE; + + __print_mce(m); + + return NOTIFY_DONE; +} + +static struct notifier_block mce_default_nb = { + .notifier_call = mce_default_notifier, + /* lowest prio, we want it to run last. */ + .priority = 0, +}; + /* * Read ADDR and MISC registers. */ @@ -2138,6 +2177,7 @@ int __init mcheck_init(void) { mcheck_intel_therm_init(); mce_register_decode_chain(&mce_srao_nb); + mce_register_decode_chain(&mce_default_nb); mcheck_vendor_init_severity(); INIT_WORK(&mce_work, mce_process_work); -- 2.20.1