RE: [git pull] x86 PAT changes

[Linus Torvalds]

On Sat, 26 Apr 2008, Pallipadi, Venkatesh wrote:
> 
> Agreed that NONPROMISC_DEVMEM is not really needed for read/write. But,
> we will still need it for /dev/mem.

If so, just disable it unconditionally for mmap.

As mentioned, that's really just a return to original Linux /dev/mmap 
semantics: long ago (well, not _that_ long ago) we never used to be able 
to mmap() normal kernel memory, because the page counts would get screwed 
up on pages that weren't marked PG_Reserved.

So the traditional Linux behavior for mmap() on /dev/mem was always to 
only allow it on memory that either had no "struct page *" backing at all, 
or that was marked PG_Reserved (ie the ISA hole ay 640k-1M and things like 
the BIOS tables etc).

Going back to that doesn't sound horrible.

		Linus
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