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[Launchpad Bug Tracker <1826453@xxxxxxxxxxxxxxxxxx>]

This bug was fixed in the package grub2-signed - 1.66.22

---------------
grub2-signed (1.66.22) xenial; urgency=medium

  * Rebuild against grub2 2.02~beta2-36ubuntu3.22. (LP: #1826453)

 -- Mathieu Trudel-Lapierre <cyphermox@xxxxxxxxxx>  Tue, 30 Apr 2019
11:16:33 -0400

** Changed in: grub2-signed (Ubuntu Xenial)
       Status: Fix Committed => Fix Released

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https://bugs.launchpad.net/bugs/1826453

Title:
  Grub2 Booting in blind mode due to "invalid video mode specification
  `text'"

Status in grub2 package in Ubuntu:
  Fix Released
Status in grub2-signed package in Ubuntu:
  Fix Released
Status in grub2 source package in Trusty:
  New
Status in grub2-signed source package in Trusty:
  New
Status in grub2 source package in Xenial:
  Fix Released
Status in grub2-signed source package in Xenial:
  Fix Released

Bug description:
  [Impact]
  UEFI users booting VMs on Hyper-V

  [Test case]
  1) Install Ubuntu 16.04 in a Gen2 VM on Hyper-V (Windows)
  2) After install; edit /etc/default/grub to add:
  GRUB_GFXPAYLOAD_LINUX="text"
  3) Run 'sudo update-grub'
  4) Reboot

  Verify whether the system writes an error/warning on console during
  boot (this shows up and disappears quickly, one must watch the console
  attentively):

  error: invalid video mode specification `text'.
  Booting in blind mode

  
  [Regression potential]
  There is minimal risk of regression; this is a patch that has been succesfully used in other releases to address the same issue (see bug 1711452). It only affects graphical payload selection in grub to avoid a value that is clearly invalid, thus skipping the error value and falling back to the default text-mode. Care should be taking while testing to identify any possible issues with displaying the grub menu or outputting information from the kernel at console as the system boots (if applicable).

  ---

  In a Ubuntu 16.04.6 VM, which runs as a Gen2 VM on Hyper-V, I add
  GRUB_GFXPAYLOAD_LINUX="text" into /etc/default/grub and run update-
  grub; next, grub2 prints the below error:

  error: invalid video mode specification `text'.
  Booting in blind mode

  This means grub2 passes a zero value for the "lfb_base" to Linux
  kernel, which then fails to reserve the framebuffer MMIO range in
  drivers/hv/vmbus_drv.c: vmbus_reserve_fb(); as a result, when we pass
  through a PCIe device to the VM, the PCIe device may get a PCI MMIO
  BAR in the FB MMIO range, causing a conflict, and the PCIe device can
  not work in the VM.

  The issue can not reproduce with Ubuntu 18.04. It turns out the grub2 in Ubuntu 18.04 has the below fix:
  video: skip 'text' gfxpayload if not supported, to fallback to default (https://git.launchpad.net/~ubuntu-core-dev/grub/+git/ubuntu/commit/?id=38d9e2f862a96a039ae8ca8b87b8615d154ceda4).

  I'm asking the patch author (Mathieu Trudel-Lapierre) to submit the
  patch to the upstream grub and this is the upstream bug link:
  https://savannah.gnu.org/bugs/?56217 .

  Here this launchpad bug is for Ubuntu 16.04 and 14.04.

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