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yuvadm

Member

From: Tel Aviv-Jaffa, Israel

Registered: 2012-08-08

Posts: 102

Website

Intel microcode updating and reverting back

I just installed microcode updates for my Intel Skylake CPU laptop (Thinkpad X260). Now, after some uptime, I'm seeing this:

$ dmesg | grep microcode
[    0.000000] microcode: microcode updated early to revision 0xba, date = 2017-04-09
[    0.877885] microcode: sig=0x406e3, pf=0x80, revision=0xba
[    0.878145] microcode: Microcode Update Driver: v2.2.
[ 2947.382888] microcode: sig=0x406e3, pf=0x80, revision=0x9e
[ 2947.383961] microcode: updated to revision 0xba, date = 2017-04-09
[ 2947.397481] microcode: sig=0x406e3, pf=0x80, revision=0xba
[ 9171.073636] microcode: sig=0x406e3, pf=0x80, revision=0x9e
[ 9171.083635] microcode: sig=0x406e3, pf=0x80, revision=0xba
[ 9201.280874] microcode: sig=0x406e3, pf=0x80, revision=0x9e
[ 9201.295332] microcode: sig=0x406e3, pf=0x80, revision=0xba
[15215.238214] microcode: sig=0x406e3, pf=0x80, revision=0x9e
[15215.252805] microcode: sig=0x406e3, pf=0x80, revision=0xba
[18982.405762] microcode: sig=0x406e3, pf=0x80, revision=0x9e
[18982.419404] microcode: sig=0x406e3, pf=0x80, revision=0xba

Why is microcode always changing back and forth between the old and new version?

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 21,616

Re: Intel microcode updating and reverting back

Are you suspending in between? Afaik it has to be reapplied on wakeup, which is what you are seeing.

Last edited by V1del (2017-07-03 12:40:29)

yuvadm

Member

From: Tel Aviv-Jaffa, Israel

Registered: 2012-08-08

Posts: 102

Website

Re: Intel microcode updating and reverting back

Yes those most likely are suspends. Weird behavior, I wouldn't expect that.

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 21,616

Re: Intel microcode updating and reverting back

Why not? During a suspend you shut off the CPU, it loses the volatile firmware patches, and they get reapplied when CPU wakes up again.

yuvadm

Member

From: Tel Aviv-Jaffa, Israel

Registered: 2012-08-08

Posts: 102

Website

Re: Intel microcode updating and reverting back

Right, so I wonder why the microcode patches are volatile. Or will they become permanent after the next reboot?

LaurentvdB

Member

Registered: 2017-04-24

Posts: 32

Re: Intel microcode updating and reverting back

Right, so I wonder why the microcode patches are volatile. Or will they become permanent after the next reboot?

Microcode updates are always volatile. They never become permanent and have to be reapplied every time the CPU is turned on.

The reason why they do this is because Microcode is stored in the Control unit of the CPU. As microcode is used quite heavily in a CPU (and has a large influence on the performance) they use highly efficient and very fast storage for this that loses all its data when powered off (compare it with RAM).

Lone_Wolf

Member

From: Netherlands, Europe

Registered: 2005-10-04

Posts: 11,910

Re: Intel microcode updating and reverting back

The only way i know for microcode changes to become semi-permanent[1] is if the motherboard manufacturer implementes the changes in bios/uefi firmware and releases it.

[1]
The changes still have to be applied on each boot, but it's done earlier in the boot process and transparent to the user.

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Disliking systemd intensely, but not satisfied with alternatives so focusing on taming systemd.

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R00KIE

Forum Fellow

From: Between a computer and a chair

Registered: 2008-09-14

Posts: 4,734

Re: Intel microcode updating and reverting back

If you are not on bios version 1.29 then download the update iso[1] and update your bios. It might contain the latest microcode and as a bonus you probably get some bug fixes.

[1] http://pcsupport.lenovo.com/pt/en/produ … /downloads

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R00KIE
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HiImTye

Member

From: Halifax, NS, Canada

Registered: 2012-05-09

Posts: 1,072

Re: Intel microcode updating and reverting back

a second reason why they aren't made permanent is that if there's any breakage, you can always revert. the same is not necessarily true of a bios/uefi update. the way it is is both functional, and safe.