Re: [Xen-devel] [PATCH] x86/mm: remove the linear mapping of the p2m tables

[Keir Fraser <keir.xen@xxxxxxxxx>]

On 13/09/2012 15:42, "Tim Deegan" <tim@xxxxxxx> wrote:

>> Is that also going to remain true when we won't be able to 1:1-
>> map all of the memory anymore once we break the current 5Tb
>> barrier? If not, it would probably be worthwhile keeping that
>> code.
> 
> Ah, 5TB is a smaller limit than I thought we had.  Yes, better leave it
> alone, so.  Though TBH finding some way to use a bit more virtual
> address space for Xen seems like a good idea anyway, since this won't be
> the only place we'll want to avoid TLB flushes.

For HVM or PVH guests, where this HAP code would be used, clearly Xen can
use all the virtual address space it wants. It will almost certainly make
sense for Xen to have a 1:1 physical mapping of all memory when running such
a guest, and only do mapcache type tricks when running legacy PV guests.

 -- Keir



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