linux-kernel - Re: [PATCH] x86/mce: Increase maximum number of banks to 64

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Date:   Thu, 20 Aug 2020 13:00:54 -0500
From:   Yazen Ghannam <yazen.ghannam@....com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-edac@...r.kernel.org, linux-kernel@...r.kernel.org,
        tony.luck@...el.com, x86@...nel.org,
        Smita.KoralahalliChannabasappa@....com
Subject: Re: [PATCH] x86/mce: Increase maximum number of banks to 64

On Thu, Aug 20, 2020 at 07:15:18PM +0200, Borislav Petkov wrote:
> On Thu, Aug 20, 2020 at 05:06:24PM +0000, Yazen Ghannam wrote:
> > From: Akshay Gupta <Akshay.Gupta@....com>
> > 
> > ...because future AMD systems will support up to 64 MCA banks per CPU.
> > 
> > MAX_NR_BANKS is used to allocate a number of data structures, and it is
> > used as a ceiling for values read from MCG_CAP[Count]. Therefore, this
> > change will have no functional effect on existing systems with 32 or
> > fewer MCA banks per CPU.
> 
> Of course it will, grep for MAX_NR_BANKS and look at all those bitmaps
> and arrays which get defined with MAX_NR_BANKS size. With your change,
> they will double in size.
> 
> How much does vmlinux size grow with your change?
>

It seems to get smaller.

-rwxrwxr-x   1 yghannam yghannam 807634088 Aug 20 17:51 vmlinux-32banks
-rwxrwxr-x   1 yghannam yghannam 807634072 Aug 20 17:50 vmlinux-64banks

Any ideas? Maybe there's some alignment change? Or a build issue on my
end?

Thanks,
Yazen