[ANNOUNCE] Xen 4.15 - call for notification/status of significant bugs

[Ian Jackson <iwj@xxxxxxxxxxxxxx>]

Although there are a few things outstanding, we are now firmly into
the bugfixing phase of the Xen 4.15 release.

I searched my email (and my memory) and found four open blockers which
I have listed below, and one closed blocker.

I feel there are probably more issues out there, so please let me
know, in response to this mail, of any other significant bugs you are
aware of.

Ian.


OPEN ISSUES
-----------

A. HPET/PIT issue on newer Intel systems

Information from
  Andrew Cooper <andrew.cooper3@xxxxxxxxxx>

| This has had literally tens of reports across the devel and users
| mailing lists, and prevents Xen from booting at all on the past two
| generations of Intel laptop.  I've finally got a repro and posted a
| fix to the list, but still in progress.

I think Andrew is still on the case here.


B. "scheduler broken" bugs.

Information from
  Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  Dario Faggioli <dfaggioli@xxxxxxxx>

Quoting Andrew Cooper
| We've had 4 or 5 reports of Xen not working, and very little
| investigation on whats going on.  Suspicion is that there might be
| two bugs, one with smt=0 on recent AMD hardware, and one more
| general "some workloads cause negative credit" and might or might
| not be specific to credit2 (debugging feedback differs - also might
| be 3 underlying issue).

I reviewed a thread about this and it is not clear to me where we are
with this.


C. Fallout from MSR handling behavioral change.

Information from
  Jan Beulich <jbeulich@xxxxxxxx>

I am lacking an extended desxcription of this.  What are the bug(s),
and what is the situation ?


D. Use-after-free in the IOMMU code

Information from
  Julien Grall <julien@xxxxxxx>
References
 [PATCH for-4.15 0/4] xen/iommu: Collection of bug fixes for IOMMU teadorwn
 <20201222154338.9459-1-julien@xxxxxxx>

Quoting the 0/:
| This series is a collection of bug fixes for the IOMMU teardown code.
| All of them are candidate for 4.15 as they can either leak memory or
| lead to host crash/host corruption.

AFAIT these patches are not yet in-tree.



CLOSED ISSUES
=============

E. zstd support

Information from
  Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
  Jan Beulich <jbeulich@xxxxxxxx>
  git

Needed to unbreak Fedora.  Needs support for both dom0 and domU.

AFAICT this seems to be in-tree as of 8169f82049ef
"libxenguest: support zstd compressed kernels"