[Bug 1882774] Re: issues with secondary VMX execution controls

[Łukasz Zemczak]

Hello Christian, or anyone else affected,

Accepted qemu into focal-proposed. The package will build now and be
available at https://launchpad.net/ubuntu/+source/qemu/1:4.2-3ubuntu6.3
in a few hours, and then in the -proposed repository.

Please help us by testing this new package.  See
https://wiki.ubuntu.com/Testing/EnableProposed for documentation on how
to enable and use -proposed.  Your feedback will aid us getting this
update out to other Ubuntu users.

If this package fixes the bug for you, please add a comment to this bug,
mentioning the version of the package you tested, what testing has been
performed on the package and change the tag from verification-needed-
focal to verification-done-focal. If it does not fix the bug for you,
please add a comment stating that, and change the tag to verification-
failed-focal. In either case, without details of your testing we will
not be able to proceed.

Further information regarding the verification process can be found at
https://wiki.ubuntu.com/QATeam/PerformingSRUVerification .  Thank you in
advance for helping!

N.B. The updated package will be released to -updates after the bug(s)
fixed by this package have been verified and the package has been in
-proposed for a minimum of 7 days.

** Changed in: qemu (Ubuntu Focal)
       Status: Triaged => Fix Committed

** Tags added: verification-needed verification-needed-focal

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https://bugs.launchpad.net/bugs/1882774

Title:
  issues with secondary VMX execution controls

Status in Ubuntu Cloud Archive:
  New
Status in qemu package in Ubuntu:
  Fix Released
Status in qemu source package in Focal:
  Fix Committed

Bug description:
  [Impact]

  In qemu 4.2 was a change [1] meant to improve the handling of MSRs vs CPUID.
  It was later identified [2] as an issue and fixed.
  This has to be backported to Focal to resolve that issue on several platforms.

  An example where this occurs is:
  - Azure instances with nested virt
  - GCP instances with nested virt

  We have seen a bunch of qemu named CPU types that can expose similar behavior when used on chips that pretend to be of some type e.g. Skylake but miss some of their features to be settable.
  It isn't entirely sure thou that this will be fixed by the same - yet worth to mention.

  The impact is that qemu 4.2 as in Ubuntu 20.04 doesn't work on those
  platforms bailing out.

  [1]: https://github.com/qemu/qemu/commit/048c95163b472ed737a2f0dca4f4e23a82ac2f8a
  [2]: https://github.com/qemu/qemu/commit/4a910e1f6ab4155ec8b24c49b2585cc486916985

  [Test Case]

   * Get a GCP or Azure instance with nested virtualization enabled
   * Spawn a KVM guest on it e.g. by using uvtool-libvirt using a named type 
     matching the cpu
     e.g. if the host reports as skylake use such a type.
     You can use `virsh domcapabilities` to check what the host is
     detected as.

  [Regression Potential]

   * It is a bit hard to guess, but it should not make things worse. But if I'd expect one then the
     VMX subfeatures could change on cases not intended to. Yet we should have one of two cases:
     a) the common one is that the host can set this and has done so, it will continue as before
     b) host was unable to set these and failed, this should now work with the fix in place
     Both seem ok to me.

  [Other Info]

   * there might be a local (non cloud) way to reproduce but I don't
  know it yet

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