[Xen-devel] PoD issue

["Jan Beulich" <JBeulich@xxxxxxxxxx>]

George,

before diving deeply into the PoD code, I hope you have some idea that
might ease the debugging that's apparently going to be needed.

Following the comment immediately before p2m_pod_set_mem_target(),
there's an apparent inconsistency with the accounting: While the guest
in question properly balloons down to its intended setting (1G, with a
maxmem setting of 2G), the combination of the equations

  d->arch.p2m->pod.entry_count == B - P
  d->tot_pages == P + d->arch.p2m->pod.count

doesn't hold (provided I interpreted the meaning of B correctly - I
took this from the guest balloon driver's "Current allocation" report,
converted to pages); there's a difference of over 13000 pages.
Obviously, as soon as the guest uses up enough of its memory, it
will get crashed by the PoD code.

In two runs I did, the difference (and hence the number of entries
reported in the eventual crash message) was identical, implying to
me that this is not a simple race, but rather a systematical problem.

Even on the initial dump taken (when the guest was sitting at the
boot manager screen), there already appears to be a difference of
800 pages (it's my understanding that at this point the difference
between entries and cache should equal the difference between
maxmem and mem).

Does this ring any bells? Any hints how to debug this? In any case
I'm attaching the full log in case you want to look at it.

Jan

Attachment: xen.log.1
Description: Binary data

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