HVM troubleshooting

HVM pauses on boot, followed by kernel error

The HVM may pause on boot, showing a fixed cursor. After a while a series of warnings may be shown similar to this:

BUG: soft lockup - CPU#0 stuck for 23s! [systemd-udevd:244]

To fix this:

  1. Kill the HVM.
  2. Start the HVM
  3. Press “e” at the grub screen to edit the boot parameters
  4. Find the /vmlinuz line, and edit it to replace “rhgb” with “modprobe.blacklist=bochs_drm”
  5. Press “Ctrl-x” to start the HVM

If this solves the problem then you will want to make the change permanent:

  1. Edit the file /etc/default/grub.

  2. Find the line which starts:

     GRUB_CMDLINE_LINUX=

  3. Remove this text from that line:

     rhgb

  4. Add this text to that line:

     modprobe.blacklist=bochs_drm

  5. Run this command:

     grub2-mkconfig --output=/boot/grub2/grub.cfg

The HVM should now start normally.

Can’t start an OS in an HVM / “Probing EDD (edd=off to disable!… ok” message

If you see a screen popup with SeaBios and 4 lines, last one being Probing EDD (edd=off to disable!... ok, then enter the following command from a dom0 prompt:

qvm-prefs <HVMname> kernel ""

HVM crashes when booting from ISO

If your HVM crashes when trying to boot an ISO, first ensure that ` qvm-prefs kernel` is empty, as shown above. If this doesn't help, then disable memory balancing and set the minimum memory to 2GB.

You can disable memory-balancing in the settings, under the “Advanced” tab.

To give the VM a RAM of 2GB, open a terminal in dom0 and enter:

qvm-prefs <HVMname> memory 2000

Attached devices in Windows HVM stop working on suspend/resume

After the whole system gets suspended into S3 sleep and subsequently resumed, some attached devices may stop working. To know how to make the devices work, see Suspend/resume Troubleshooting.