Bug 193241

Summary:	Microcode device /dev/cpu/microcode doesn't exist?
Product:	[Fedora] Fedora	Reporter:	Robert Scheck <redhat-bugzilla>
Component:	kernel	Assignee:	Jon Masters <jcm>
Status:	CLOSED RAWHIDE	QA Contact:
Severity:	medium	Docs Contact:
Priority:	medium
Version:	rawhide	CC:	hgbug
Target Milestone:	---
Target Release:	---
Hardware:	i686
OS:	Linux
Whiteboard:
Fixed In Version:	2.6.23-0.157.rc4.git2	Doc Type:	Bug Fix
Doc Text:		Story Points:	---
Clone Of:		Environment:
Last Closed:	2007-09-05 22:10:29 UTC	Type:	---
Regression:	---	Mount Type:	---
Documentation:	---	CRM:
Verified Versions:		Category:	---
oVirt Team:	---	RHEL 7.3 requirements from Atomic Host:
Cloudforms Team:	---	Target Upstream Version:
Embargoed:

Description Robert Scheck 2006-05-26 14:55:47 UTC

Description of problem:
> service microcode_ctl start
Applying Intel CPU microcode update: /etc/init.d/microcode_ctl: microcode
device /dev/cpu/microcode doesn't exist?
> 

And yepp, the script is correct:

> ls -l /dev/cpu*
ls: /dev/cpu*: No such file or directory
>

WHY is this the case?! CPU is:
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 2
model name      : Intel(R) Xeon(TM) CPU 3.06GHz
stepping        : 9
cpu MHz         : 3066.228
cache size      : 512 KB
[...]

Version-Release number of selected component (if applicable):
microcode_ctl-1.13-1.30

How reproducible:
Everytime, see above.

Actual results:
Microcode device /dev/cpu/microcode doesn't exist.

Expected results:
Existing microcode device /dev/cpu/microcode or similar ;-)

Additional info:
Maybe this bug is assigned to the wrong component, reassign to kernel, udev
or whatever fits if needed - thank you.

Comment 1 Jon Masters 2006-09-01 04:55:57 UTC

I need to know the version of the kernel that you are running this against so
that I can try to track down why that device does not exist. Please let me know.

Comment 2 Robert Scheck 2006-09-01 11:31:04 UTC

2.6.17-1.2293_FC6 - which is pretty old now. But it was up2date when I wrote 
this bug report...

Comment 3 Hong-Gunn Chew 2007-04-05 05:55:23 UTC

It seems that the microcode module is not created in fc6.  Something might have
changed since fc5 to make the decision to remove the module?

config-2.6.18-1.2798.fc6:
# CONFIG_MICROCODE is not set
config-2.6.20-1.2933.fc6:
# CONFIG_MICROCODE is not set

Comment 4 Robert Scheck 2007-07-15 19:43:21 UTC

PING?

Comment 5 Jon Masters 2007-08-20 06:38:42 UTC

This is a potential bug in the kernel config. Both in xen and non-xen kernels
(in the case of Xen, the hypervisor needs a fix to do microcode updates...and
even then, it's implemented incorrectly wrt. how it should be done in Xen, but
that requires a complete re-architecting of Xen itself to fix).

Jon.

Comment 6 Robert Scheck 2007-08-20 20:57:40 UTC

Well...it isn't of belong to me. Novell has microcode_ctl working with and 
without Xen, so why aren't we able? I'm not sure, what you would like to hear 
from me but: This is no notabug, no cantfix, no wontfix...but: Assigned :)

Comment 7 Jon Masters 2007-08-20 22:11:00 UTC

Yes, but it's not a bug in the microcode package. It's a "bug" in the
kernel/hypervisor.

Note that I'm not saying it doesn't work, I'm saying that the Xen implementation
of microcode updates is known to be insufficient in the longer term - it works,
but I've been told that, once the CPU is in VT mode, that you should not be
trying to update the microcode after that...it should be done in the hypervisor
well before booting the first DomU or even Dom0. It's not a Novell-vs-RedHat
thing. It's just that Xen will need some tweaking in future to handle this IMO.

Jon.

Comment 8 Robert Scheck 2007-09-05 22:10:29 UTC

$ grep CONFIG_MICROCODE /boot/config-2.6.23-0.157.rc4.git2
CONFIG_MICROCODE=m
CONFIG_MICROCODE_OLD_INTERFACE=y
$