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

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Date:	Thu, 21 Feb 2008 15:46:56 -0800
From:	Jeremy Fitzhardinge <jeremy@...p.org>
To:	"H. Peter Anvin" <hpa@...or.com>
CC:	"Eric W. Biederman" <ebiederm@...ssion.com>,
	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>,
	Andi Kleen <andi@...stfloor.org>,
	Mika Penttila <mika.penttila@...umbus.fi>
Subject: Re: 2.6.25-rc1 xen pvops regression

H. Peter Anvin wrote:
> Jeremy Fitzhardinge wrote:
>>
>> It seems to me that those pages are being handed out as heap pages by 
>> the early allocator.  In the Xen case this is OK because there's 
>> nothing magic about them.  But if real hardware doesn't reserve these 
>> pages in the E820 map, then they could end up being used as regular 
>> memory by mistake, which is an issue.
>>
>
> No, they couldn't.
>
> On real hardware they'll be memory types 0 or 2, depending on whether 
> or not they're marked reserved.
>
> Available RAM is type 1. 

OK.  Well, perhaps Ian's patch could be amended to test to see if the 
e820 map marks the ISA ROM region as normal RAM, and skip it if so?

    J
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