A user has reported extensive performance issues with a Lenovo Thinkpad
X1 Extreme Gen 2 laptop computer, in bug 1973434. The user reports video
playback hangs, browser hangs and virtual machines hanging.

Their dmesg indicates the system has 2x IOMMUs and there are 25 groups
being configured. They tested "intel_iommu=off", and the performance
issues are no longer seen.

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https://bugs.launchpad.net/bugs/1971699

Title:
  disable Intel DMA remapping by default

Status in linux package in Ubuntu:
  Invalid
Status in linux source package in Jammy:
  In Progress

Bug description:
  [Impact]

  It seems that enabling Intel IOMMU can cause some weird gfx problems, see for 
example:
      
   https://bugs.launchpad.net/bugs/1971146
   https://bugs.launchpad.net/bugs/1965882

  [Test case]

  We don't have any specific test case, only other bug reports that
  tracked down the origin of the issue as being introduced when
  CONFIG_INTEL_IOMMU_DEFAULT_ON has been enabled by default.

  [Fix]

  Revert "UBUNTU: [Config] enable Intel DMA remapping options by
  default"

  [Regression potential]

  DMA remapping device not present at boot by default, users that
  require this feature will need to specifically add intel_iommu=on to
  the kernel boot parameters to enable it.

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