[Bug 1915288] Re: grub 2.04 net does not like deployments with kvm maas pods

[Dimitri John Ledkov]

Sideloaded http://archive.ubuntu.com/ubuntu/dists/focal-
proposed/main/uefi/grub2-amd64/2.04-1ubuntu26.9/grubnetx64.efi.signed
onto maas deployment machine.

Composed a further 10 machines, and they all reached READY state and
powered off without a hitch.

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https://bugs.launchpad.net/bugs/1915288

Title:
  grub 2.04  net does not like deployments with kvm maas pods

Status in grub2 package in Ubuntu:
  Fix Committed
Status in grub2 source package in Focal:
  Fix Committed
Status in grub2 source package in Groovy:
  Fix Committed

Bug description:
  [Impact]

   * MAAS KVM LXD pods fail to deploy, in very beefy servers.

   1) cherrypick upstream fix that caused crash upon completion of http
  networking

   2) revert patches that add support for TCP window scaling and non-
  ethernet cards

  With above changes one can deploy 100 out of 100 MAAS KVM LXD pods
  using the patched grubnetx86.efi

  
  [Test Case]

   * Configure maas

   * Configure networking for lxd kvm pods

   * Deploy ubuntu focal on a node

   * Manually init lxd, allow netowrking, add remote password

   * Add kvm lxd host in the kvm page of maas

   * Disable image syncing in maas

   * replace /var/snap/maas/common/maas/boot-
  resources/current/bootloader/uefi/amd64/grubx64.efi with the signed
  grubnetx64.efi.signed from the grub-efi-amd64-signed package

   * compose & commision hundred nodes with cli api:

  for i in `seq 100`; do maas ps5 vmhost compose 8; done

  (where 8 is the id of the kvm host, see url for the kvm node in
  question)

  Without these patches failure rate is up to 30%. With these patches
  100 out of 100 pods deploy fine.

  Thus one should be ok testing with less number of pods too.

  [Where problems could occur]

   * These patches mean that we are using smaller (same ones we did in
  bionic) TCP window, thus for very large kernels/initrds we may hit
  http timeouts on the server. Also it means that throughput speed of
  deployments is lower again.

  * However it is better to deploy where we used to deploy before, than
  failing to deploy small things on small networks.

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