Ubuntu
grub2 package

  1. Bug #1826453
  2. Comment #0

Comment 0 for bug 1826453

Revision history for this message
Dexuan Cui (decui) wrote :

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.