Re: [PATCH v3 2/2] x86/mce: Rate-limit the CMCI storm transition notices

[Sohil Mehta <sohil.mehta@intel.com>]

On 11/13/2026 4:49 AM, Breno Leitao wrote:
> mce_track_storm() prints a line every time a bank enters storm mode and
> another every time it leaves. Neither is bounded, so the log volume
> follows whatever rate the bank flaps at.
> 
> One host in our fleet logged 9970726 "CMCI storm detected" and 9970734
> "CMCI storm subsided" lines for a single bank over four days, which is
> a bit excessive for all monitoring purposes.
> 
> Put both transitions behind one ratelimit.
> 
> Acked-by: Tony Luck <tony.luck@intel.com>
> Signed-off-by: Breno Leitao <leitao@debian.org>
> ---

Reviewed-by: Sohil Mehta <sohil.mehta@intel.com>

A minor nit below.

>  arch/x86/kernel/cpu/mce/threshold.c | 16 ++++++++++++++--
>  1 file changed, 14 insertions(+), 2 deletions(-)
> 
> diff --git a/arch/x86/kernel/cpu/mce/threshold.c b/arch/x86/kernel/cpu/mce/threshold.c
> index 6c370d5af5bd23..8591715ce24306 100644
> --- a/arch/x86/kernel/cpu/mce/threshold.c
> +++ b/arch/x86/kernel/cpu/mce/threshold.c
> @@ -4,6 +4,7 @@
>   */
>  #include <linux/interrupt.h>
>  #include <linux/kernel.h>
> +#include <linux/ratelimit.h>
>  
>  #include <asm/irq_vectors.h>
>  #include <asm/traps.h>
> @@ -111,6 +112,13 @@ void cmci_storm_end(unsigned int bank)
>  		mce_timer_kick(false);
>  }
>  
> +/*
> + * Shared by both transitions so that a bank flapping between them cannot
> + * outrun the console.
> + */
> +static DEFINE_RATELIMIT_STATE(storm_rs, DEFAULT_RATELIMIT_INTERVAL,
> +			      DEFAULT_RATELIMIT_BURST);
> +

Should this be defined as a function local similar to patch 1?

>  void mce_track_storm(struct mce *mce)
>  {
>  	struct mca_storm_desc *storm = this_cpu_ptr(&storm_desc);
> @@ -150,13 +158,17 @@ void mce_track_storm(struct mce *mce)
>  	if (storm->banks[mce->bank].in_storm_mode) {
>  		if (history & GENMASK_ULL(STORM_END_POLL_THRESHOLD, 0))
>  			return;
> -		printk_deferred(KERN_NOTICE "CPU%d BANK%d CMCI storm subsided\n", smp_processor_id(), mce->bank);
> +		if (__ratelimit(&storm_rs))
> +			printk_deferred(KERN_NOTICE "CPU%d BANK%d CMCI storm subsided\n",
> +					smp_processor_id(), mce->bank);
>  		mce_handle_storm(mce->bank, false);
>  		cmci_storm_end(mce->bank);
>  	} else {
>  		if (hweight64(history) < STORM_BEGIN_THRESHOLD)
>  			return;
> -		printk_deferred(KERN_NOTICE "CPU%d BANK%d CMCI storm detected\n", smp_processor_id(), mce->bank);
> +		if (__ratelimit(&storm_rs))
> +			printk_deferred(KERN_NOTICE "CPU%d BANK%d CMCI storm detected\n",
> +					smp_processor_id(), mce->bank);
>  		mce_handle_storm(mce->bank, true);
>  		cmci_storm_begin(mce->bank);
>  	}
>