linux-kernel - Re: [all better] Re: regression: massive trouble with fpu rework

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Date:	Mon, 29 Jun 2015 10:33:02 +0200
From:	Borislav Petkov <bp@...en8.de>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
Cc:	Ingo Molnar <mingo@...nel.org>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>,
	"H. Peter Anvin" <hpa@...or.com>,
	Thomas Gleixner <tglx@...utronix.de>,
	Andy Lutomirski <luto@...nel.org>,
	Denys Vlasenko <dvlasenk@...hat.com>,
	Oleg Nesterov <oleg@...hat.com>, Dave Hansen <dave@...1.net>
Subject: Re: [all better] Re: regression: massive trouble with fpu rework

On Mon, Jun 29, 2015 at 10:25:29AM +0200, Mike Galbraith wrote:
> On Mon, 2015-06-29 at 08:40 +0200, Ingo Molnar wrote:
> > *
> > Ok, so could you please move the fpu__init_system() further up and see which 
> > position is that starts breaking with the BIOS option set?
> > 
> > here's the current, broken layout of the code:
> > 
> >         get_cpu_cap(c);
> > [0]     fpu__init_system(c);
> > 
> >         if (this_cpu->c_early_init)
> >                 this_cpu->c_early_init(c);

> [0] is the only spot that breaks box.

I bet it is that

        /* Unmask CPUID levels if masked: */
        if (c->x86 > 6 || (c->x86 == 6 && c->x86_model >= 0xd)) {
                if (msr_clear_bit(MSR_IA32_MISC_ENABLE,
                                  MSR_IA32_MISC_ENABLE_LIMIT_CPUID_BIT) > 0) {
                        c->cpuid_level = cpuid_eax(0);
                        get_cpu_cap(c);
                }
        }

in early_init_intel(). If you feel like playing, you might comment it
out to see what happens.

:-)

-- 
Regards/Gruss,
    Boris.

ECO tip #101: Trim your mails when you reply.
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