linux-kernel - Re: [PATCH v3 17/17] x86/mce: Restore poll settings after storm subsides

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Message-ID: <20250512154315.GC2355@yaz-khff2.amd.com>
Date: Mon, 12 May 2025 11:43:15 -0400
From: Yazen Ghannam <yazen.ghannam@....com>
To: Borislav Petkov <bp@...en8.de>
Cc: x86@...nel.org, Tony Luck <tony.luck@...el.com>,
	linux-kernel@...r.kernel.org, linux-edac@...r.kernel.org,
	Smita.KoralahalliChannabasappa@....com,
	Qiuxu Zhuo <qiuxu.zhuo@...el.com>
Subject: Re: [PATCH v3 17/17] x86/mce: Restore poll settings after storm
 subsides

On Mon, May 12, 2025 at 09:46:16AM +0200, Borislav Petkov wrote:
> On Tue, Apr 15, 2025 at 02:55:12PM +0000, Yazen Ghannam wrote:
> > Users can disable MCA polling by setting the "ignore_ce" parameter or by
> > setting "check_interval=0". This tells the kernel to *not* start the MCE
> > timer on a CPU.
> > 
> > During a CMCI storm, the MCE timer will be started with a fixed
> > interval.
> 
> Why?
> 
> If a user doesn't want CEs, why are we even bothering with CMCI storms?
> 
> Might as well disable the storm handling code altogether...
> 

The use case is "disable MCA polling". I just gave two examples of how
this can be done.

We can focus on "check_interval=0". The user wants to disable MCA
polling and rely only on interrupts. They still want to see the CEs.

If an interrupt storm happens, the kernel will switch to polling with
our MCE timer.

When the storm ends, the kernel should go back to how things were before
the storm. If there was a timer before, then go back to the old
interval. If there was *not* a timer before, then delete/remove the
timer.

Thanks,
Yazen