qubes-doc/external/troubleshooting/intel-igfx-troubleshooting.md

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doc	Intel Integrated Graphics Troubleshooting	/doc/intel-igfx-troubleshooting/

Intel Integrated Graphics Troubleshooting

Software Rendering or Video Lags

If you are experiencing this issue, you will see extremely slow graphics updates. You will be able to watch the screen and elements paint slowly from top to bottom. You can confirm this is the issue by looking for a line similar to the following in your /var/log/Xorg.0.log file:

[   131.769] (EE) AIGLX: reverting to software rendering

Newer versions of the Linux kernel have renamed the i915.preliminary_hw_support=1 option to i915.alpha_support=1, so if you needed this kernel option in the past you will have to rename it or add it to your configuration files (follow either GRUB2 or EFI, not both):

• GRUB2: /etc/default/grub, GRUB_CMDLINE_LINUX line and
  Rebuild grub config (grub2-mkconfig -o /boot/grub2/grub.cfg)
• EFI: /boot/efi/EFI/qubes/xen.cfg, kernel= line(s)

IOMMU

Dom0 Kernels currently included in Qubes have issues related to VT-d (IOMMU) and some versions of the integrated Intel Graphics Chip. Depending on the specific hardware / software combination the issues are quite wide ranging, from apparently harmless log errors, to VM window refresh issues, to complete screen corruption and crashes rendering the machine unusable with Qubes.

Such issues have been reported on at least the following machines:

• HP Elitebook 2540p
• Lenovo x201
• Lenovo x220
• Thinkpad T410
• Thinkpad T450s

Log errors only on :

• Librem 13v1
• Librem 15v2

The installer for Qubes 4.0 final has been updated to disable IOMMU for the integrated intel graphics by default. However, users of 3.2 may experience issues on install or on kernel upgrades to versions higher than 3.18.x.

Disabling IOMMU for the integrated graphics chip is not a security issue, as the device currently lives in dom0 and is not passed to a VM. This behaviour is planned to be changed as of Qubes 4.1, when passthrough capabilities will be required for the GUI domain ¹.

Workaround for existing systems with VT-d enabled (grub / legacy mode)

Edit the startup parameters for Xen:

1. Open a terminal in dom0
2. Edit /etc/default/grub (e.g. sudo nano /etc/default/grub)
3. Add to the line GRUB_CMDLINE_XEN_DEFAULT the setting iommu=no-igfx, save and quit
4. Commit the change withsudo grub2-mkconfig --output /boot/grub2/grub.cfg

Workaround for existing systems with VT-d enabled (UEFI)

Edit the startup parameters for Xen:

1. Open a terminal in dom0
2. Edit /boot/efi/EFI/qubes/xen.cfg (e.g. sudo nano /boot/efi/EFI/qubes/xen.cfg)
3. Add to the line options the setting iommu=no-igfx, save and quit

1 https://github.com/QubesOS/qubes-issues/issues/2841 ↩