Re: [Xen-devel] Page tables in Xen

[tgh <wwwwww4187@xxxxxxxxxxx>]

hi
 I am confused about shadow page table in the paravirtual mode in xen,
 does guestOS have all of its own processes'page tables,and  xen keeps 
the very exactly all of the guestOS's processes page tables for a copy? 
or say ,it is xen  who keeps the only copy of the guestOS's processes 
page tables ,and guestOS  accesses to its processes's page tables 
through some hypercall? or ,what about it ?
 If the guestOS has all of its processes's page talbes, while xen 
maintain the copy of all those page tables ,is it an inefficient usage 
of memory ,or what is the trick behind ?
Thanks in advance



Daniel Stodden åé:
> On Thu, 2007-11-29 at 11:00 +0530, pradeep singh rautela wrote:
>   
> > On Nov 29, 2007 1:42 AM, Haifeng He <hehaifeng2nd@xxxxxxxxx> wrote:
> >     
> > > Thanks for answering my question. I am talking about PV mode. What about shadow
> > > page table? Does it mean, Xen will keep (real) copies of page tables?
> > >       
> > Shadown page tables are employed in HVM guests not PV guests.
> >     
> regarding shadowed PV domains, there's still
> XENFEAT_auto_translated_physmap. but it's rather exotic and therefore
> rarely used.
>
> regarding the original question: yes, this means xen keeps the real page
> tables, while guests map pseudo-physical (i.e. linear) memory in what
> they (may) believe to be the real ones.
>
> regards,
> daniel
>
>   

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