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

[Ville Syrjälä]

On Thu, Oct 14, 2021 at 04:27:07PM +0200, Borislav Petkov wrote:
> On Thu, Oct 14, 2021 at 02:44:33PM +0300, Ville Syrjälä wrote:
> > I have a 32bit installation here that stopped working. Bisected it
> > to commit d298b03506d3 ("x86/fpu: Restore the masking out of reserved
> > MXCSR bits").
> 
> Lemme make sure I understand this correctly: this patch is bad and with
> it reverted it works?

Yes.

>
> Because before this patch, the restoring would be a more restrictive
> than before and this patch reverts the code to the old behavior for
> invalid MXCSR bits.
> 
> > 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.

-- 
Ville Syrjälä
Intel