linux-kernel - Re: [regression] commit d298b03506d3 ("x86/fpu: Restore the masking out of reserved MXCSR bits")

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Date:   Thu, 14 Oct 2021 16:44:27 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     Ser Olmy <ser.olmy@...tonmail.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...hat.com>,
        "H. Peter Anvin" <hpa@...or.com>, x86@...nel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [regression] commit d298b03506d3 ("x86/fpu: Restore the masking
 out of reserved MXCSR bits")

On Thu, Oct 14, 2021 at 05:34:14PM +0300, Ville Syrjälä wrote:
> > > Tested the same disk on on both a 64bit capable Pentium D
> > > and a 32bit only Pentium 4 just to rule out the specific CPU.
> > > Busted on both.
> > 
> > So that's a purely 32-bit installation and a 32-bit kernel and you've
> > booted it on two different machines?
> 
> Yes.

This is insane, grrr!

So Ser's report was about an old 32-bit Intel CPU failing:

https://lore.kernel.org/all/YVtA67jImg3KlBTw@zn.tnic/T/#u

so if we revert, it'll break booting on his machine.

Can you give /proc/cpuinfo from your machines?

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette