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Date: Thu, 5 Mar 2015 09:38:49 +0100
From: Quentin Casasnovas <quentin.casasnovas@oracle.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: Dave Hansen <dave.hansen@intel.com>,
        Quentin Casasnovas <quentin.casasnovas@oracle.com>,
        Andy Lutomirski <luto@amacapital.net>, Borislav Petkov <bp@suse.de>,
        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: <20150305083849.GP4938@chrystal.uk.oracle.com>
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:
> On 03/04, Dave Hansen wrote:
> >
> > I'm running a commit from the tip/x86/fpu branch: ae486033b98.  It's on
> > a system which I normally boot with 'noxsaves'.  When I boot without
> > 'noxsaves' it is getting a GPF around the time that init is forked off.
> 
> And I assume that (before this commit) the kernel runs fine if you boot
> without 'noxsaves'?
> 
> > 
> > The full oops is below, but addr2line points to the "alternative_input("
> > line in xrstor_state().
> > 
> > The one that oopses has this in bootup:
> > 
> >    xsave: enabled xstate_bv 0x1f, cntxt size 0x3c0 using compacted form
> > 
> > The one that works says:
> > 
> >    xsave: enabled xstate_bv 0x1f, cntxt size 0x440 using standard form
> > 
> 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...
> 

Hopefully the couple of fixes to prevent the #GP should be merged soon, but
they only cure the symptoms and not the root cause of this issue, I think.

Quentin