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

From: Borislav Petkov
Date: Thu Oct 14 2021 - 10:27:13 EST


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?

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?

--
Regards/Gruss,
Boris.

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