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    |   xen-users
Re: [Xen-users] Re: [Xen-devel] VMX Hardware 
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On 14 Aug 2005, at 19:09, Anthony Liguori wrote:
 The Pacifica spec does mention optional hardware support for "Nested 
Page Tables" which is essentially hardware shadow page tables.
Should be interesting to see the performance difference between 
software/hardware shadow page tables. 
I have doubts about the performance of hardware page tables, unless 
there's a clever TLB design. A pagetable walk which is four memory 
accesses on normal x86/64 becomes twenty accesses in nested mode! 
It may be that shadow pagetables, by providing a bigger 'cache' for 
guest->host mappings, can actually perform better on many workloads. 
I guess we'll see -- if silicon is produced that supports that mode, 
someone is bound to add support to Xen. 
 -- Keir
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