[Bug 1519836] Re: MaaS fails to boot Hyper-V Generation 2 virtual machines

Mathieu Trudel-Lapierre mathieu.tl at gmail.com
Thu May 12 20:38:39 UTC 2016

I've uploaded the suggested patch from Rigoberto Corujo and it indeed
seems to improve the timer situation to some degree even outside of the
PXE case (for example, it seems like EFI grub better handles checking
the modifier key here to get to the grub menu).

Still, I'm concerned about the impact on this if EFI SetTimer timers are
known to sometimes hang. Have you built grub2 from sources, were you
building grub2 beta3 altogether from the git tree or just taking the
patches and applying them?

I agree that commit a03c1034 is most likely insufficient to fix the
issue if PIT isn't available on gen2 hyper-V; but I think we should do
due diligence and check against all of master (if it hasn't been done
already), especially for the following patch already in grub2 git; which
seem promising:


This specifically calls out fixes for Hyper-V; and while it doesn't
attempt to make use of SetTimer; it does use Stall in TimeServices to
achieve a similar effect.

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  MaaS fails to boot Hyper-V Generation 2 virtual machines

Status in MAAS:
Status in grub2 package in Ubuntu:
  In Progress

Bug description:
  When trying to deploy a "Generation 2" virtual machine on Hyper-V,
  grub fails to fetch the linux kernel and initrd from MaaS. The
  operation times out immediately, because the Generation 2 VMs are
  missing the Programmable Interval Timer (PIT). The current version of
  grub still requires this interface to exist, in order to calculate

  There is a patch that uses the EFI SetTimer() available here:


  and an alternative in the discussion here:


  that uses pmtimer instead. I am aware that grub is a critical package.
  What is the official/proper way to fix this issue? Can a patched
  grubnetx64.efi be packaged with MaaS? Do we have to wait for this fix
  to merge?


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