Re: [RFC PATCH 02/12] PAT 64b: Basic PAT implementation

[Siddha, Suresh B]

On Thu, Dec 13, 2007 at 09:23:26PM -0700, Eric W. Biederman wrote:
> ebiederm@xxxxxxxxxxxx (Eric W. Biederman) writes:
> Ok.  My analysis here was wrong.  Currently pgprot_noncached and
> ioremap_nocache are out of sync.  With ioremap_nocache only specifying
> _PAGE_PCD and pgprot_noncached specifying _PAGE_PCD | _PAGE_PWT.
> 
> So I don't have a clue how someone could reprogram the mtrrs currently
> and expect things to work.
> 
> ...
> 
> If we bother to ask ioremap for memory that is not cached, the last
> thing in the world we want is the MTRRs upgrading that to write combining.
> So ioremap_nocache has been slightly buggy for ages.  ioremap_nocache
> and PAGE_KERNEL_NOCACHE should get _PAGE_PWT added to their
> definitions.
> 
> Could we please get a cleanup patch at the beginning of this patchset
> or that comes before it that fixes ioremap_nocache on x86?
> 
> That will make us a lot more git-bisect safe.

Ok. I will send a separate patch  fixing ioremap_nocache on x86.

thanks,
suresh
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