linux-kernel - Re: 2.6.25-rc1 xen pvops regression

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Message-ID: <47BDF0C4.10407@zytor.com>
Date:	Thu, 21 Feb 2008 13:44:36 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Ian Campbell <ijc@...lion.org.uk>,
	Joel Becker <Joel.Becker@...cle.com>,
	Jody Belka <lists-lkml@...b.org>, linux-kernel@...r.kernel.org,
	Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Andi Kleen <andi@...stfloor.org>,
	Mika Penttila <mika.penttila@...umbus.fi>
Subject: Re: 2.6.25-rc1 xen pvops regression

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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