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[Xen-ia64-devel] PMT vs. 3 level page table (was: Xen/ia64 - global or per VP VHPT)


  • To: "Magenheimer, Dan \(HP Labs Fort Collins\)" <dan.magenheimer@xxxxxx>, "Yang, Fred" <fred.yang@xxxxxxxxx>
  • From: "Dong, Eddie" <eddie.dong@xxxxxxxxx>
  • Date: Thu, 5 May 2005 21:30:32 +0800
  • Cc: ipf-xen <ipf-xen@xxxxxxxxx>, xen-ia64-devel@xxxxxxxxxxxxxxxxxxx
  • Delivery-date: Thu, 05 May 2005 13:30:07 +0000
  • List-id: DIscussion of the ia64 port of Xen <xen-ia64-devel.lists.xensource.com>
  • Thread-index: AcVKfesR741jQGkzQvWmdNAbNvskDgAAPPdQAAnH97AAJJJm8AAGJlmgACr730AABzFgcAAYTImwABTis7AAALccgAAAPutgABLQl4AAN60BYAARFB9AABDYKGAAClWscAADqFKgAK3i7sA=
  • Thread-topic: PMT vs. 3 level page table (was: Xen/ia64 - global or per VP VHPT)

Magenheimer, Dan (HP Labs Fort Collins) wrote:
> I left the 3-level page tables in for
> guest-physical-to-machine-physical because I expected physical memory
> on ia64 to generally be much 
> larger than x86 and the existing Linux method for handling VA
> spaces seemed suitable.  Is there Xen-common code for this
> that is better?  (I think this code is archdep right now, though
> I suppose it could be moved back from archdep to common if it
> is truly architecture-independent, e.g. if ppc could use it too.)
> 
Dan, maybe I didn't understand the benefit well. What is the benifit of
3 level page table?
PMT is very strightforward for VMM although it may consume more memory
in IA64 than in IA32.
In my strightforward thinking, a PMT even consume less memory than page
table.
 What is the reason for 3 level page table? 
BTW, I am assume HV always present guest linear memory space 
from 0 -- XXX except domain 0 which is directly mapped, and I guess your
3 level page table is also per
domain instance.
Eddie

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