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

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Message-ID: <47BEF7D9.50300@zytor.com>
Date:	Fri, 22 Feb 2008 08:27:05 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Alan Cox <alan@...rguk.ukuu.org.uk>,
	Ian Campbell <ijc@...lion.org.uk>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	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>,
	Mika Penttila <mika.penttila@...umbus.fi>
Subject: Re: 2.6.25-rc1 xen pvops regression

Andi Kleen wrote:
> Alan Cox wrote:
>>> Actually I switched 64bit over to trust e820 completely and not
>>> reserve 640k-1MB explicitly some time ago
>>> and AFAIK there hasn't been any reports that it causes problems.
>>>
>>> So presumably trusting e802 is ok on modern systems (2003+)
>> Apparently so - at least 64bit capable ones. 
> 
> They should all use the same BIOS code bases, except perhaps
> some embedded weirdnesses.

Well, that, plus you still have to deal with a lot older stuff.

> We do still sort the entries
>> to remove zero length records and other suprises.
> 
> That code could be actually dropped. And the sorting too.
> It's all not needed I think.

When I dealt with this for another project, I found that the e820 data 
format is suboptimal.  It's better to treat it as a sorted list of 
(address, type) tuples (where type can be zero); the data from e820 can 
be fed into such a data structure and it cleans it up nicely.

	-hpa
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