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

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Message-ID: <YWhFOJCF1pxIBANv@zn.tnic>
Date:   Thu, 14 Oct 2021 16:56:56 +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 05:43:14PM +0300, Ville Syrjälä wrote:
> Hmm. Actually I just stared at the code a bit more it looks
> a bit funny. Was it supposed to do this instead?
> 
> - fpu->state.fxsave.mxcsr &= ~mxcsr_feature_mask;
> + fpu->state.fxsave.mxcsr &= mxcsr_feature_mask;

Whoops, I had it like that in the original patch:

https://lore.kernel.org/all/163354193576.25758.8132624386883258818.tip-bot2@tip-bot2/

I blame tglx. :-)

Does it work if you remove the mask negation "~"?

-- 
Regards/Gruss,
    Boris.

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