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

[Luck, Tony]

On Mon, Aug 24, 2026 at 01:29:18AM -0700, Breno Leitao wrote:
> On Fri, Aug 21, 2026 at 09:50:19AM -0700, Luck, Tony wrote:
> 
> > > Count corrected errors per bank and add mce=panic_on_ce_count=<count>
> > > and panic the host if we have more events than set.
> > 
> > FYI. I don't think this needs to be fixed, but you should be aware and
> > perhaps document the shared bank details.
> > 
> > This won't count accurately for banks that are shared by multiple logical
> > CPUs (you've inherited this from the storm detection code that introduces
> > this problem).
> > 
> > E.g. a machine check bank reporting L2 errors is shared by both logical CPUs
> > on a core on P-core systems, and by all cores on a module on E-core systems.
> 
> Good point, thanks. I had not thought about the shared bank case.
> 
> I will document it in v2, roughly like this under panic_on_ce_count=
> in kernel-parameters.txt:
> 
>         The count is kept per CPU and per bank. A bank shared by
>         several logical CPUs -- an L2 bank is shared by the SMT
> 	siblings, for instance -- has its errors split across those
> 	CPUs.
> 
> plus a line in the changelog noting that the count inherits the
> <per-CPU,per-bank> granularity of the storm tracking. Thus, there may be
> more errors logged than you expect before your panic fires. Would it be better?

Yes. Documentation like this in the commit, and under Documentation/*
gives fair notice to users.

> One question while I am here: is the approach itself something you are
> willing to take, or, just a just send patch [1/2]?

Boris is the maintainer here. So he has the final decision. My
opinion is that this is a bit niche for the kernel. Maybe this
could be handled by some user agent (mcelog? rasdaemon?) to
raise awareness to system operators about high rates of corrected
errors.
> 
> Thanks for the review,
> --breno

-Tony