linux-kernel - Re: [PATCH] x86/fpu: Fix nofxsr regression

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Date:   Wed, 3 Jul 2019 09:24:00 +0200
From:   Sebastian Andrzej Siewior <bigeasy@...utronix.de>
To:     Thomas Gleixner <tglx@...utronix.de>
Cc:     Andi Kleen <andi@...stfloor.org>, x86@...nel.org,
        linux-kernel@...r.kernel.org, Andi Kleen <ak@...ux.intel.com>,
        Vegard Nossum <vegard.nossum@...cle.com>
Subject: Re: [PATCH] x86/fpu: Fix nofxsr regression

On 2019-07-03 00:17:17 [+0200], Thomas Gleixner wrote:
> On Tue, 2 Jul 2019, Andi Kleen wrote:
> >  
> > -	if (cmdline_find_option_bool(boot_command_line, "nofxsr")) {
> > +	if (!IS_ENABLED(CONFIG_64BIT) &&
> > +		cmdline_find_option_bool(boot_command_line, "nofxsr")) {
> > +		fpu__xstate_clear_all_cpu_caps();
> >  		setup_clear_cpu_cap(X86_FEATURE_FXSR);
> >  		setup_clear_cpu_cap(X86_FEATURE_FXSR_OPT);
> >  		setup_clear_cpu_cap(X86_FEATURE_XMM);
> 
> This is a mixture of disabling features explicitely and having the
> dependencies in cpuid-deps. Even 2 of the existing ones are pointless
> because clear(FXSR) already clears the other two.
> 
> Why not make XSAVE depend on XMM or whatever is the right dependency?

I have something half way done.

> Thanks,
> 
> 	tglx

Sebastian