Re: [Xen-devel] Re: [PATCH 1 of 7] x86: add _PAGE_IOMAP pte flagfor IO mappings

From: Avi Kivity
Date: Wed Sep 10 2008 - 05:55:37 EST

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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