Re: [PATCH 2/2] x86/mce: Add mce=panic_on_ce_count to panic on a corrected error flood

On Fri, Aug 21, 2026 at 03:24:08AM -0700, Breno Leitao wrote:
> +/*
> + * A bank that keeps reporting corrected errors is repairing them faster than
> + * anything acts on it. Count them and let the admin put a ceiling on it.
> + */
> +void mce_track_ce_count(struct mce *mce)
> +{
> +	struct storm_bank *bank = &this_cpu_ptr(&storm_desc)->banks[mce->bank];
> +	int limit = READ_ONCE(mca_cfg.panic_on_ce_count);
> +
> +	if (limit <= 0)
> +		return;
> +
> +	if (!(mce->status & MCI_STATUS_VAL) || !mce_is_correctable(mce))
> +		return;
> +
> +	if (++bank->ce_count < (u64)limit)

If errors are happening faster than Linux can service CMCI interrupts,
then the corrected error count in bits {52:38} will be some number
bigger than "1".[*] You should add that number here, rather than simply
incrementing +bank->ce_count.

> +		return;
> +
> +	printk_deferred(KERN_EMERG "CPU%d BANK%d logged %llu corrected errors\n",
> +			smp_processor_id(), mce->bank, bank->ce_count);
> +	mce_panic("Too many corrected errors", NULL, NULL);
> +}
> +
>  void mce_track_storm(struct mce *mce)
>  {
>  	struct mca_storm_desc *storm = this_cpu_ptr(&storm_desc);
> 
> -- 
> 2.53.0-Meta

-Tony

[*] My personal record is several hundred. But that was on a debug
system that had been poked to signal an error on every cache access!