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

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Message-ID: <20150627082514.GA10894@gmail.com>
Date:	Sat, 27 Jun 2015 10:25:14 +0200
From:	Ingo Molnar <mingo@...nel.org>
To:	Mike Galbraith <umgwanakikbuti@...il.com>
Cc:	Ingo Molnar <mingo@...e.hu>, LKML <linux-kernel@...r.kernel.org>
Subject: Re: [all better] Re: regression: massive trouble with fpu rework


* Mike Galbraith <umgwanakikbuti@...il.com> wrote:

> On Sat, 2015-06-27 at 08:25 +0200, Mike Galbraith wrote:
> > Hi Ingo,
> > 
> > My i7-4790 box is having one hell of a time with this merge window, is
> > dead in the water.
> 
> BIOS setting "Limit CPUID Maximum" upsets new fpu code mightily.

Ok, that's interesting. Mind explaining it a bit more verbosely - which setting is 
causing what?

This would suggest sensitivity on CPUID details, i.e. that doing 
fpu__init_system() before other CPU init sequences is causing the bug.

Does the patch below perhaps make a difference? (I'd suggest to apply it _without_ 
the other patch I sent.)

Thanks,

	Ingo

 arch/x86/kernel/cpu/common.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/common.c b/arch/x86/kernel/cpu/common.c
index 9fc5e3d9d9c8..922c5e0cea4c 100644
--- a/arch/x86/kernel/cpu/common.c
+++ b/arch/x86/kernel/cpu/common.c
@@ -742,7 +742,6 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 	cpu_detect(c);
 	get_cpu_vendor(c);
 	get_cpu_cap(c);
-	fpu__init_system(c);
 
 	if (this_cpu->c_early_init)
 		this_cpu->c_early_init(c);
@@ -754,6 +753,7 @@ static void __init early_identify_cpu(struct cpuinfo_x86 *c)
 		this_cpu->c_bsp_init(c);
 
 	setup_force_cpu_cap(X86_FEATURE_ALWAYS);
+	fpu__init_system(c);
 }
 
 void __init early_cpu_init(void)
--
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