qubes-doc/managing-os/linux-hvm-tips.md

layout	title	permalink	redirect_from
doc	Linux HVM Tips	/doc/linux-hvm-tips/	/en/doc/linux-hvm-tips/ /doc/LinuxHVMTips/ /wiki/LinuxHVMTips/

Tips for Linux in HVM domain

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

Tested with Qubes R3.2-RC3 Issue may be related to "bochs_drm" video driver.

To fix:

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 no longer display the error if it's related to the "bochs_drm" kernel driver.

Screen resolution

Some kernel/Xorg combination use only 640x480 in HVM, which is quite small. To enable maximum resolution, some changes in Xorg configuration are needed:

1. Force "vesa" video driver
2. Provide wide horizontal synchronization range

To achieve it (all commands run as root):

1. Generate XOrg configuration (if you don't have it):

   X -configure :1 && mv ~/xorg.conf.new /etc/X11/xorg.conf
   

2. Add HorizSync line to Monitor section, it should look something like:

   Section "Monitor"
           Identifier   "Monitor0"
           VendorName   "Monitor Vendor"
           ModelName    "Monitor Model"
           HorizSync    30.0 - 60.0
   EndSection
   

3. Change driver to "vesa" in Device section:

   Section "Device"
           # (...)
           Identifier  "Card0"
           Driver      "vesa"
           VendorName  "Technical Corp."
           BoardName   "Unknown Board"
           BusID       "PCI:0:2:0"
   EndSection
   

Now you should get at least 1280x1024 and be able to choose other modes.

Qubes agents

Linux Qubes agents are written with PV domain in mind, but it looks to be possible to run them also in HVM domain. However some work is required to achieve it. Check this thread.