Linux 3.3-rc4 Kernel Fixes A Peculiar 32-bit Bug
Written by Michael Larabel in Linux Kernel on 18 February 2012 at 08:22 PM EST. 3 Comments
The Linux 3.3-rc4 kernel was released this Saturday evening after a peculiar 32-bit kernel bug had led to the release being delayed by a few days.

Linus Torvalds and others spent the past few days tracking down a complicated issue with the Linux 3.3 kernel whereby there would be floating-point state corruption resulting in a range of nasty problems. This FP corruption would result in crashes, Flash problems within the browser, the X input cursor moving sporadically, or other random issues.

This issue was tracked down to using a 32-bit x86 kernel on modern CPUs that support the AES-NI instruction set. Besides needing to be on a 32-bit AES-NI-capable kernel for CPUs that support the Advanced Encryption Standard instruction set, you also need to be using a wireless kernel driver that can utilize this hardware-acceleration for Advanced Encryption Standard encryption/decryption. When all these factors are met, you might have encountered this bug, which is fortunately now expected to be addressed in 3.3-rc4 and should in time be back-ported to stable kernels.

Intel supports AES-NI on their modern Sandy Bridge and most Clarkdale/Arrandale/Gulftown CPUs and AMD provides support for AES-NI with Bulldozer. All of these CPUs support x86_64, so you really should be using a 64-bit Linux kernel anyways and not a 32-bit kernel. If you still are using a 32-bit kernel on recent Intel/AMD hardware you should really consider moving to a 64-bit x86 kernel.

Besides fixing this 32-bit-kernel-with-AES-NI-and-WiFi-driver-causing-havoc bug, the 3.3-rc4 carries a variety of other bug-fixes too. There isn't anything else that stands out too much, although the old GMA500 driver was removed from staging now that there's the better Poulsbo driver. The old POHMELFS code was also dropped since now there's the new POHMELFS file-system.

One graphics-related note is that the Intel DRM driver with the Linux 3.3-rc4 kernel has decided to disable frame-buffer compression (FBC) for Sandy Bridge hardware as it's causing BLT ring problems with it running many times slower (up to 100x slower) or frequent lock-ups. The Intel developers aren't sure why having FBC causes the problem for Sandy Bridge, but this is their interim fix.

The Linux 3.3-rc4 kernel release announcement can be read at LKML.org. Some of the new features of the forthcoming Linux 3.3 kernel are talked about in this Phoronix article.
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Michael Larabel is the principal author of Phoronix.com and founded the site in 2004 with a focus on enriching the Linux hardware experience. Michael has written more than 10,000 articles covering the state of Linux hardware support, Linux performance, graphics drivers, and other topics. Michael is also the lead developer of the Phoronix Test Suite, Phoromatic, and OpenBenchmarking.org automated benchmarking software. He can be followed via Twitter or contacted via MichaelLarabel.com.

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