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

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Date:	Mon, 29 Jun 2015 14:27:23 +0200
From:	Mike Galbraith <umgwanakikbuti@...il.com>
To:	Borislav Petkov <bp@...en8.de>
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, 2015-06-29 at 10:33 +0200, Borislav Petkov wrote:

> 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.

With it commented out, and fpu__init_system() either back at previously
booting position [5] or at original [0], doesn't matter, box is dead,
but differently.  It stalls after setting clocksource to tsc, and just
sits there.

	-Mike


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