CentOS IOMMU related errors on system boot

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CentOS IOMMU related errors on system boot

On booting CentOS, RHEL or Fedora it is possible to receive large number of messages of

   PTE read access is not set

This is caused by some problem with IOMMU unit. This can be avoided (not solved) by disabling IOMMU altogether. This requires editing /etc/grub/grub.conf file and removing

   intel_iommu=on
   amd_iommu=on

options.

Note that ignoring these message flooding is not a good idea. This will cause /var/log/messages flie to become very big, system to be very slow due to continuous disk write of these log messages and would make debugging things that require /var/log/messages to be read very difficult.

This was learned from http://www.gossamer-threads.com/lists/linux/kernel/1647852