Re: [Xen-devel] Commit moratorium to staging

[Ian Jackson <ian.jackson@xxxxxxxxxxxxx>]

So, investigations (mostly by Roger, and also a bit of archaeology in
the osstest db by me) have determined:

* This bug is 100% reproducible on affected hosts.  The repro is
  to boot the Windows guest, save/restore it, then migrate it,
  then shut down.  (This is from an IRL conversation with Roger and
  may not be 100% accurate.  Roger, please correct me.)

* Affected hosts differ from unaffected hosts according to cpuid.
  Roger has repro'd the bug on an unaffected host by masking out
  certain cpuid bits.  There are 6 implicated bits and he is working
  to narrow that down.

* It seems likely that this is therefore a real bug.  Maybe in Xen and
  perhaps indeed one that should indeed be a release blocker.

* But this is not a regresson between master and staging.  It affects
  many osstest branches apparently equally.

* This test is, effectively, new: before the osstest change
  "HostDiskRoot: bump to 20G", these jobs would always fail earlier
  and the affected step would not be run.

* The passes we got on various osstest branches before were just
  because those branches hadn't tested on an affected host yet.  As
  branches test different hosts, they will stick on affected hosts.

ISTM that this situation would therefore justify a force push.  We
have established that this bug is very unlikely to be anything to do
with the commits currently blocked by the failing pushes.

Furthermore, the test is not intermittent, so a force push will be
effective in the following sense: we would only get a "spurious" pass,
resulting in the relevant osstest branch becoming stuck again, if a
future test was unlucky and got an unaffected host.  That will happen
infrequently enough.

So unless anyone objects (and for xen.git#master, with Julien's
permission), I intend to force push all affected osstest branches when
the test report shows the only blockage is ws16 and/or win10 tests
failing the "guest-stop" step.

Opinions ?

Ian.

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