RE: Transparent paravirtualization vs. xen paravirtualization(was:RE: [Xen-ia64-devel] IRQ management)

["Yang, Fred" <fred.yang@xxxxxxxxx>]

Magenheimer, Dan (HP Labs Fort Collins) wrote:
>> Key issue on
>> gnttab is Domain0 should also have PMT table support, which shouldn't
>> access machine physical with gpn=mpn directly.  This issue is also
>> the key reason causing major effort in porting VBD/DomainU for
>> each upstream
>> merge.  This also blocks the forward VNIF effort due to page
>> flipping issue. PMT is a must for gnttab to support VBD, VNIF and
>> forward 
>> development of
>> Xen/ia64.   PMT would need to be shared between Domain and Xen for
>> performance
> 
> I guess I disagree.  I've seen all the patches for each upstream
> merge and it doesn't look to me as if a major design change
> is required, just a clarification of the arch-specific boundaries.
> 
> Could you explain what you mean by "blocks the forward VNIF effort
> due to page flipping issue"?  Page flipping should work just fine
> in the current design; Matt had it almost working (out of tree)
> before he went back to school.
The last couple effort  in getting DomainU up were mainly VBD is
directly using mpn which is customized for Xen/IPF without PMT on
Domain.
VNIF is to swap machine pages between DomainU and Domain0 during
runtime, where Domain0 is assuming machine pages doesn't change below
it.  Can you share how to address this issue?  We have been puzzeled by
this for a while.

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