Re: [Xen-devel] [PATCH 00/11] Alternate p2m: support multiple copies of host p2m

["Jan Beulich" <JBeulich@xxxxxxxx>]

>>> On 15.01.15 at 19:23, <edmund.h.white@xxxxxxxxx> wrote:
> On 01/15/2015 08:15 AM, Tim Deegan wrote:
>> - Feature compatibilty/completeness.  You pointed out yourself that
>>   it doesn't work with nested HVM or migration.  I think I'd have to
>>   add mem_event/access/paging and PCI passthrough to the list of
>>   features that ought to still work.  I'm resigned to the idea that
>>   many new features don't work with shadow pagetables. :)
>> 
> 
> The intention is that mem_event/access should still work. I haven't
> specifically looked at paging, but I don't see any fundamental reason
> why it shouldn't. PCI passthrough I suspect won't. Does nested HVM
> work with migration? Is it simply not acceptable to submit a feature
> as experimental, with known compatibility issues? I had assumed that
> it was, based on the nested HVM status as documented in the release
> notes.

It is generally acceptable, sure. But the sad thing here is that
particularly with such code coming from Intel (with the nested
VMX code being a good example, and certain IOMMU/pass-
through things being another) my experience is that once that
initial code drop happened, interest from the original authors is
lost (possibly not maliciously, but because of being assigned other
tasks) and the code therefore has to remain experimental for
extended periods of time (often until someone else gets
frustrated enough about its half baked state to spend non-
negligible amounts of time to deal with the loose ends).

Jan


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