Re: [patch] do_no_pfn

[Andi Kleen <ak@suse.de>]

On Tuesday 20 June 2006 10:01, Jes Sorensen wrote:
> Robin Holt wrote:
> > On Mon, Jun 19, 2006 at 03:06:05PM +0200, Andi Kleen wrote:
> >> The big question is - why do you have pages without struct page? 
> >> It seems ... wrong.
> [snip]
> > Are you saying the for the mspec pages we should extend the vmem_map,
> > partially populate the regions for the mspec pages, mark those pages as
> > uncached and reserved and then turn them over to the uncached allocator?
> > Seems like we have done a lot of extra work to put a struct page behind
> > a page which requires special handling.
> 
> Note that Bjorn Helgas has a case where he needs this as well.
> 
> We could fake the pages by giving them a struct page, but it really
> makes no point as you say.

I think it would be better if you gave them struct pages instead 
of messing up core vm with such strange hooks.

Or alternatively code this in a different way. There are drivers
who map IO memory into user space without needing hacks like that.
Usually they just tweak the page tables directly on mmap.

-Andi