[CentOS-virt] how to update ucode with xen

Wed Sep 19 18:08:46 UTC 2018
Kevin Stange <kevin at steadfast.net>

On 9/19/18 1:55 AM, Christoph wrote:
> Hi
> can someone say me how to update the µcode of the cpu with xen?
> I have added the ucode=scan parameter to xen but it does not seem to
> work...
> the µcode version of my xeon is really old :/
> model name    : Intel(R) Xeon(R) CPU E3-1271 v3 @ 3.60GHz
> microcode    : 0x10

There is a "caveat" in the current version of microcode_ctl which means
it doesn't automatically install the microcode into the initramfs if the
kernel isn't "known good" because of various issues with Linux kernel
patches being needed for certain microcode features.  There is a quick
way to get it to force the microcode into the initramfs of any kernel:

mkdir -p /etc/microcode_ctl/ucode_with_caveats/
touch /etc/microcode_ctl/ucode_with_caveats/force

This only works with the most recent version of microcode_ctl
(2.1-29.16.el7_5.x86_64).  If you do this, you can then run 'yum
reinstall microcode_ctl' and you should get the microcode in the
initramfs after it finishes.  Note that this will cause it to trust ALL
kernels and all microcode versions which might not always be a good
thing.  See this file for info:


You can test that the initramfs has the microcode by running cpio:

cpio -t < /boot/initramfs-4.9.112-32.el7.x86_64.img

If there is a GenuineIntel.bin you should be good.  If you get spammed
with errors, then it isn't included.

Kevin Stange
Chief Technology Officer
Steadfast | Managed Infrastructure, Datacenter and Cloud Services
800 S Wells, Suite 190 | Chicago, IL 60607
312.602.2689 X203 | Fax: 312.602.2688
kevin at steadfast.net | www.steadfast.net