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Did Your System Take A Dive With Linux 3.2?

Linux Kernel

Published on 05 January 2012 04:58 PM EST
Written by Michael Larabel in Linux Kernel
32 Comments

If you upgraded today to the just-released Linux 3.2 kernel and your Intel system is now having problems booting this new kernel release, you're not alone, but here's a possible workaround.

A regression struck the Linux 3.2 kernel concerning IOMMU and is still present in the final release of Linux 3.2. The issue didn't appear during the 3.2 merge window but later on in the cycle (if my memory serves me when I first struck the issue, it was around -rc2 or -rc3) and results in the kernel not successfully booting.

If you're running Ubuntu (or likely other distributions too with a splash screen) on the Linux 3.2 kernel it may just seem like your system never boots. Or that it's caught in a panic, but it's an infinite loop. If viewing the text output of the Linux 3.2 kernel, you will see a continuous stream of "DMAR:[DMA Read] Request device [17:00.0] fault addr ffffff000" (or similar) and "DMAR:[fault reason 02] Present bit in context entry is clear" messages fill your screen indefinitely.

Did Your System Take A Dive With Linux 3.2?


The system locally that I often use where I've been hitting this issue with the Linux 3.2 kernel is a ThinkPad W510 notebook with an Intel Core i7 CPU and NVIDIA Quadro graphics. This is the first time I've been hitting this particular issue in several years of using the W510 and with a wide range of kernels. Fortunately, there is a workaround by setting "intel_iommu=off" as a kernel parameter when booting the system. If disabling Intel IOMMU within GRUB, the system should then boot without the DMAR issue.

Did Your System Take A Dive With Linux 3.2?


Setting "intel_iommu=off" though disables Intel VT-d / I/O virtualization support. (On many systems you can also disable Intel VT-d from the BIOS/UEFI. Or you could also just stick to the Linux 3.1 kernel or older if you really don't care.) This feature on modern Intel hardware seems to be rather problematic with the Linux 3.2 kernel.

Disabling Intel IOMMU has been fixing some Intel GPU hangs and other problems too from this latest kernel (Intel was also using the IOMMU state as the basis for determining RC6 support until that was later reverted in 3.2). I'm not the only one experiencing this Intel IOMMU issue that's been present for several weeks. It's already been brought up today in the forums as well.

Hopefully the issue(s) will get sorted out for the Linux 3.3 kernel and back-ported to Linux 3.2 before more users are affected when upgrading to Ubuntu 12.04 LTS and other releases being based upon the 3.2 kernel.

About The Author
Michael Larabel is the principal author of Phoronix.com and founded the web-site in 2004 with a focus on enriching the Linux hardware experience and being the largest web-site devoted to Linux hardware reviews, particularly for products relevant to Linux gamers and enthusiasts but also commonly reviewing servers/workstations and embedded Linux devices. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics hardware drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated testing software. He can be followed via and or contacted via .
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