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---
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layout: doc
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title: Linux HVM Tips
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permalink: /doc/linux-hvm-tips/
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redirect_from:
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- /en/doc/linux-hvm-tips/
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- /doc/LinuxHVMTips/
- /wiki/LinuxHVMTips/
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---
Tips for Linux in HVM domain
============================
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How to fix bootup kernel error
-------------------------------
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This concerns the following:
BUG: soft lockup - CPU#0 stuck for 23s! [systemd-udevd:244]
This has been tested with Qubes `R3.2-RC3` . Note that the issue may be related
to the `bochs_drm` video driver. To fix this:
1. Edit the file `/etc/default/grub` .
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2. Find the line which starts:
~~~
GRUB_CMDLINE_LINUX=
~~~
3. Remove this text from that line:
~~~
rhgb
~~~
4. Add this text to that line:
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~~~
modprobe.blacklist=bochs_drm
~~~
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5. Run this command:
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~~~
grub2-mkconfig --output=/boot/grub2/grub.cfg
~~~
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The HVM should no longer display the error if it's related to the `bochs_drm`
kernel driver.
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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):
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1. Generate XOrg configuration (if you don't have it):
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~~~
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X -configure :1 & & mv ~/xorg.conf.new /etc/X11/xorg.conf
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~~~
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2. Add HorizSync line to Monitor section, it should look something like:
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~~~
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Section "Monitor"
Identifier "Monitor0"
VendorName "Monitor Vendor"
ModelName "Monitor Model"
HorizSync 30.0 - 60.0
EndSection
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~~~
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3. Change driver to "vesa" in Device section:
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~~~
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Section "Device"
# (...)
Identifier "Card0"
Driver "vesa"
VendorName "Technical Corp."
BoardName "Unknown Board"
BusID "PCI:0:2:0"
EndSection
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~~~
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Now you should get at least 1280x1024 and be able to choose other modes.
Qubes agents
------------
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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 ](https://groups.google.com/group/qubes-devel/browse_thread/thread/081df4a43e49e7a5 ).
