linux-kernel - Re: Oops with tip/x86/fpu

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Date:	Wed, 4 Mar 2015 21:06:12 +0100
From:	Borislav Petkov <bp@...e.de>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Dave Hansen <dave.hansen@...el.com>,
	Quentin Casasnovas <quentin.casasnovas@...cle.com>,
	Andy Lutomirski <luto@...capital.net>,
	Ingo Molnar <mingo@...nel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	Pekka Riikonen <priikone@....fi>,
	Rik van Riel <riel@...hat.com>,
	Suresh Siddha <sbsiddha@...il.com>,
	LKML <linux-kernel@...r.kernel.org>,
	"Yu, Fenghua" <fenghua.yu@...el.com>
Subject: Re: Oops with tip/x86/fpu

On Wed, Mar 04, 2015 at 08:06:51PM +0100, Oleg Nesterov wrote:
> Thanks. I'll try to investigate tomorrow.
> 
> Well, the kernel crashes because xrstor_state() is buggy, Quentin already
> has a fix.
> 
> But #GP should be explained...

Could it be one of those conditions for which XRSTORS #GPs, like

"If XRSTORS attempts to load MXCSR with an illegal value, a
general-protection exception (#GP) occurs."

for example? I'm looking at the SDM section for XRSTORS.

I mean, math_state_restore() does init_fpu() and down that road we're
allocating an FPU state ... but we did init_fpu() before too, in
eager_fpu_init(). So what changed?

Maybe I'm looking in a totally wrong direction, it is too late here to
stare at FPU code anyway...

Thanks.

-- 
Regards/Gruss,
    Boris.

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