qubes-doc/user/troubleshooting/hvm-troubleshooting.md

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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 <HVMname> 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