Message-ID: <47BDF0C4.10407@zytor.com>
Date: Thu, 21 Feb 2008 13:44:36 -0800
From: "H. Peter Anvin" <hpa@zytor.com>
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To: Jeremy Fitzhardinge <jeremy@goop.org>
CC: Ian Campbell <ijc@hellion.org.uk>, Joel Becker <Joel.Becker@oracle.com>,
       Jody Belka <lists-lkml@pimb.org>, linux-kernel@vger.kernel.org,
       Ingo Molnar <mingo@elte.hu>, Thomas Gleixner <tglx@linutronix.de>,
       "Eric W. Biederman" <ebiederm@xmission.com>,
       Andi Kleen <andi@firstfloor.org>,
       Mika Penttila <mika.penttila@kolumbus.fi>
Subject: Re: 2.6.25-rc1 xen pvops regression
References: <20080212235404.GY7980@pimb.org> <47B2DBA5.6030001@goop.org>	 <20080214022744.GA4160@mail.oracle.com> <47B3F2DC.8080707@goop.org>	 <20080215202336.GE26034@mail.oracle.com>	 <1203274161.27987.6.camel@localhost.localdomain>	 <20080218104025.GA15899@ca-server1.us.oracle.com>	 <1203458366.26910.15.camel@cthulhu.hellion.org.uk>	 <47BBDA20.8030105@zytor.com>	 <1203497511.26910.39.camel@cthulhu.hellion.org.uk>	 <47BCA275.7000504@goop.org> <1203546597.26910.74.camel@cthulhu.hellion.org.uk> <47BDEA11.6010302@goop.org> <47BDEB57.5040203@zytor.com> <47BDEF36.8000903@goop.org>
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Jeremy Fitzhardinge wrote:
> H. Peter Anvin wrote:
>>> Still curious about why a pagetable page is ending up in that range 
>>> though.  Seems like it shouldn't be possible, since we shouldn't be 
>>> allowed to allocate from those pages, at least until the DMI probe 
>>> has happened...  Unless the early allocator is only excluded from 
>>> e820 reserved pages, which would cause a problem on systems which 
>>> don't reserve the DMI space...  HPA?
>>>
>>
>> I thought the problem was a Xen-provided pagetable from before Linux 
>> started? 
> 
> Hm, I don't think so.  The domain-builder pagetable is put after the 
> kernel, so it shouldn't be under 1M.
> 

That's weird, then.  If we put a page table at 0xf0000, it would crash 
hard on real hardware (there is ROM there); as I mentioned, I do have 
hardware which both reserves and doesn't reserve this region.

	-hpa
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