linux-kernel - RE: [PATCH] x86/mce: Handle varying MCA bank counts

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Date:   Wed, 1 Aug 2018 15:40:59 +0000
From:   "Ghannam, Yazen" <Yazen.Ghannam@....com>
To:     "Luck, Tony" <tony.luck@...el.com>
CC:     "linux-edac@...r.kernel.org" <linux-edac@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "bp@...e.de" <bp@...e.de>, "x86@...nel.org" <x86@...nel.org>
Subject: RE: [PATCH] x86/mce: Handle varying MCA bank counts

> -----Original Message-----
> From: Luck, Tony <tony.luck@...el.com>
> Sent: Friday, July 27, 2018 5:09 PM
> To: Ghannam, Yazen <Yazen.Ghannam@....com>
> Cc: linux-edac@...r.kernel.org; linux-kernel@...r.kernel.org; bp@...e.de;
> x86@...nel.org
> Subject: Re: [PATCH] x86/mce: Handle varying MCA bank counts
> 
> On Fri, Jul 27, 2018 at 04:40:09PM -0500, Yazen Ghannam wrote:
> > -	/* Don't support asymmetric configurations today */
> > -	WARN_ON(mca_cfg.banks != 0 && b != mca_cfg.banks);
> > -	mca_cfg.banks = b;
> > +	mca_cfg.banks = max(mca_cfg.banks, b);
> 
> Should we change mca_cfg.banks to be a per-cpu variable?
> 
> 	DEFINE_PER_CPU(int, mce_num_banks);
> 
> That would make it easier to make sure the places
> that scan all banks only look at the ones that exist.
> 

I agree and I'd like to do that in future patches. But it'll require changes in
a few other places, and possibly breaking more assumptions in the code.

I'd like to address this issue in a smaller patch and submit it to the stable
branches. And we can redo things as per_cpu going forward.

Thanks,
Yazen