Re: proposed cpuctl modification

[Robert Elz <kre%munnari.OZ.AU@localhost>]

    Date:        Thu, 9 Mar 2023 16:21:53 +0900
    From:        Masanobu SAITOH <msaitoh%execsw.org@localhost>
    Message-ID:  <38ae66bd-1b37-c0ef-5a43-52e0c0a2a13a%execsw.org@localhost>

  | Alder Lake-N? 4 E-cores share one microcode image. I have i7-12700 and it
  | has 4 E-cores. Those 4 cores share one microcode image.

Mine is an i9-12900KS which has 8 of them (2 groups of 4).

Thanks for the confirmation, that is what looked to be happening, but
I was just guessing from what I observed.  I just use intel processors
(and others on occasion) I don't even pretend to understand them.

  | I think your idea is the best. Thank you for your commit.

No problem.  It was not a difficult change to make!

  | Another solutions is that the kernel returns 0 instead of EEXIST if the
  | version number is the same as the running microcode's version.

Yes, I considered that one as well, but as you indicate, doing that just
loses information, and gains nothing - the same number of sys calls (ioctl's)
would be performed, all that would be saved is the check to see if the
error is EEXIST when that happens (ie: peanuts).

kre

ps: do your E-cores ever just turn themselves off?   On mine, occasionally,
and for no reason I can fathom, the BIOS reports there are none of them.
(and NetBSD doesn't see them either). They come back after a power cycle.
This is probably a BIOS issue, but ?