Re: [Xen-devel] [RFC PATCH] xen/arm: Vmap allocator fails to allocate beyond 128M

[Ian Campbell <ian.campbell@xxxxxxxxxx>]

On Mon, 2015-02-23 at 17:03 +0000, Ian Campbell wrote:
> MAP_SMALL_PAGES in no way indicates to me "create the PT structure but
> do not map any actual data pages". It is documented on x86 as "don't use
> superpages mappings", which doesn't imply anything to me about
> non-superpage mappings either.

OK I get it now, MAP_SMALL_PAGES is actually a modifier for the PAGE_*
stuff, what's special about this particular usage is that it is a bare
MAP_SMALL_PAGES, i.e. not PAGE_HYPERVISOR|MAP_SMALL_PAGES.

Being bare it then lacks the present bit from PAGE_HYPERVISOR. It's a
bit like saying PAGE_NONE|MAP_SMALL_PAGES (if PAGE_NONE existed)

> Can we along with this fix perhaps rename to something which does
> indicate this. MAP_NON_LEAF_PTS or something perhaps? (This is really a
> question for Jan).

So this then doesn't make any sense, as I'm sure Jan is about to tell
me ;-)

Ian.


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