Updated microcode_ctl packages that fix a bug and add various enhancements are now available for Red Hat Enterprise Linux 6.
The microcode_ctl packages provide utility code and microcode data to assist the kernel in updating the CPU microcode at system boot time. This microcode supports all current x86-based, Intel 64-based, and AMD64-based CPU models. It takes advantage of the mechanism built-in to Linux that allows microcode to be updated after system boot. When loaded, the updated microcode corrects the behavior of various processors, as described in processor specification updates issued by Intel and AMD for those processors.
Previously, a udev rule in /lib/udev/rules.d/89-microcode.rules allowed the module to load more than once. On very large systems (for example, systems with 2048 or more CPUs), this could result in the system becoming unresponsive on boot. With this update, the udev rule has been changed to ensure the module loads only once. Very large systems now boot as expected.
The Intel CPU microcode file has been updated to version 20120606.
The AMD CPU microcode file has been updated to version 20120910.
All users of microcode_ctl are advised to upgrade to these updated packages, which fix this bug and add these enhancements. Note: a system reboot is necessary for this update to take effect.