Linux 5.19 Frowns On x86/x86_64 Late Microcode Loading - "It's Just Lottery & Broken"

[sinepgib]

This is mostly a thing for people refusing to use an initrd.

You can avoid using an initrd and do early loading of microcode with the right kernel command line.

[carewolf]

Why would people refuse to use an initrd? Why do you suppose someone would prefer the alternative?

Single kernel image.. I used to do that decades ago when playing around with Linux, but honestly it was just laziness.

[jbranso]

This is mostly a thing for people refusing to use an initrd.

Why would people refuse to use an initrd? Why do you suppose someone would prefer the alternative?

[s_j_newbury]

This is mostly a thing for people refusing to use an initrd.

[stormcrow]

It might be relevant for high availability applications. Where having to restart the servers for a microcode update is enough to make a (unwelcome) difference.
But Linus is right: late microcode loading should not come at the expense of a less stable system.

I doubt high availability is relevant to this particular patch set, however. Most built-for-many-nines hardware has the ability to cycle nodes in and out of service without interfering with the overall availability. This means late loading of microcode is still irrelevant. Trying to load microcode on-the-fly with consumer or lower-end server hardware is just asking for trouble as the patch notes (and you) state. The race conditions could indeed be catastrophic.

[Rabiator]

I can't imagine why you'd want to load the proper microcode after your CPU starts doing stuff...

It might be relevant for high availability applications. Where having to restart the servers for a microcode update is enough to make a (unwelcome) difference.
But Linus is right: late microcode loading should not come at the expense of a less stable system.

[bug77]

I can't imagine why you'd want to load the proper microcode after your CPU starts doing stuff...

[rene]

thankfully t2 Linux support early microcode loading out of the box: https://www.youtube.com/watch?v=ev1-k2PDGpg

[phoronix]

Phoronix: Linux 5.19 Frowns On x86/x86_64 Late Microcode Loading - "It's Just Lottery & Broken"

A last minute change sent in on Sunday and merged prior to Linux 5.19-rc1 disables late microcode loading by default for x86/x86_64 processors over its sad state of affairs...

https://www.phoronix.com/scan.php?page=news_item&px=Linux-5.19-Late-ucode-Loading