Re: [patch 05/21] Xen-paravirt: paravirt_ops: allocate a fixmap slot

Jeremy Fitzhardinge
2007-02-14T01:36:26Z

Dan Hecht wrote:
> Why doesn't Xen allocate the shared_info page from the pseudo-physical
> space? Doesn't it already have to steal pages from the
> pseudo-physical space for e.g. initial page tables, console, etc? Why
> not do the same for shared_info, and then you don't need a reserve the
> fixmap slot.

Unlike the pagetable pages or the console page, the shared info page
doesn't have a pseudo-physical address, so in order to map it we need to
directly construct a pte containing the mfn for that page. Inserting
this mapping into the fixmap space seems like the easiest way to do
this. It's not like a fixmap slot costs anything.

J