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

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Message-ID: <alpine.DEB.2.21.1907030013130.1802@nanos.tec.linutronix.de>
Date:   Wed, 3 Jul 2019 00:17:17 +0200 (CEST)
From:   Thomas Gleixner <tglx@...utronix.de>
To:     Andi Kleen <andi@...stfloor.org>
cc:     x86@...nel.org, linux-kernel@...r.kernel.org,
        Andi Kleen <ak@...ux.intel.com>,
        Vegard Nossum <vegard.nossum@...cle.com>,
        Sebastian Andrzej Siewior <bigeasy@...utronix.de>
Subject: Re: [PATCH] x86/fpu: Fix nofxsr regression

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?

Thanks,

	tglx