linux-kernel - Re: [Xen-devel] Re: [PATCH 1 of 7] x86: add _PAGE

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Message-ID: <48C7998D.1030408@qumranet.com>
Date:	Wed, 10 Sep 2008 12:55:25 +0300
From:	Avi Kivity <avi@...ranet.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Ingo Molnar <mingo@...e.hu>,
	Xen Devel <xen-devel@...ts.xensource.com>,
	Andi Kleen <andi@...stfloor.org>, linux-kernel@...r.kernel.org,
	"H. Peter Anvin" <hpa@...or.com>
Subject: Re: [Xen-devel] Re: [PATCH 1 of 7] x86: add _PAGE_IOMAP pte flag
 for IO	mappings

Avi Kivity wrote:
>>
>> I'm not sure; I still don't really understand how _PAGE_SPECIAL gets
>> used, other than being user-mode mapping only.  But in principle,
>> _PAGE_IOMAP could be set on both kernel and user mappings (if you direct
>> map a device into a process address space), so I think they would
>> conflict then?
>>
>>   
>
> It's a "don't refcount me" flag, which is not sematically the same as 
> I/O, but may be close enough.

Actually it's more of a "no struct page" flag, which implies no 
refcounting.  And not having a struct page should correspond well to a 
pte not requiring pfn->mfn conversion and being an I/O page.

-- 
error compiling committee.c: too many arguments to function

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