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Date: Wed, 4 Mar 2015 21:06:12 +0100
From: Borislav Petkov <bp@suse.de>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
        Quentin Casasnovas <quentin.casasnovas@oracle.com>,
        Andy Lutomirski <luto@amacapital.net>, Ingo Molnar <mingo@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        Pekka Riikonen <priikone@iki.fi>, Rik van Riel <riel@redhat.com>,
        Suresh Siddha <sbsiddha@gmail.com>,
        LKML <linux-kernel@vger.kernel.org>,
        "Yu, Fenghua" <fenghua.yu@intel.com>
Subject: Re: Oops with tip/x86/fpu
Message-ID: <20150304200612.GO3663@pd.tnic>
References: <54F74F59.5070107@intel.com>
 <20150304190651.GA5589@redhat.com>
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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.
--