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

[Jeremy Fitzhardinge <jeremy@xxxxxxxx>]

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

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