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

[Breno Leitao <leitao@debian.org>]

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?

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

Thanks for the review,
--breno