Re: [PATCH 1/3] x86: Honour passed pgprot in track_pfn_insert() and track_pfn_remap()

[Andy Lutomirski]

On Mon, Jan 25, 2016 at 9:25 AM, Matthew Wilcox
<matthew.r.wilcox@xxxxxxxxx> wrote:
> From: Matthew Wilcox <willy@xxxxxxxxxxxxxxx>
>
> track_pfn_insert() overwrites the pgprot that is passed in with a value
> based on the VMA's page_prot.  This is a problem for people trying to
> do clever things with the new vm_insert_pfn_prot() as it will simply
> overwrite the passed protection flags.  If we use the current value of
> the pgprot as the base, then it will behave as people are expecting.
>
> Also fix track_pfn_remap() in the same way.

Well that's embarrassing.  Presumably it worked for me because I only
overrode the cacheability bits and lookup_memtype did the right thing.

But shouldn't the PAT code change the memtype if vm_insert_pfn_prot
requests it?  Or are there no callers that actually need that?  (HPET
doesn't, because there's a plain old ioremapped mapping.)

--Andy