[elrepo] kernel-lt and microcode updates

[Akemi Yagi]

On Thu, Jun 18, 2020 at 9:33 AM Orion Poplawski <orion at nwra.com> wrote:

> Hello -
>
> I was poking around and noticed some differences in microcode output in
> dmesg
> between the stock EL7 kernel and kernel-lt:
>
> dmesg-3.10.0-1127.10.1.el7.x86_64:
> [    0.000000] microcode: microcode updated early to revision 0xd6, date =
> 2019-10-03
> [    5.997673] microcode: sig=0x406e3, pf=0x80, revision=0xd6
> [    5.998518] microcode: Microcode Update Driver: v2.01
> <tigran at aivazian.fsnet.co.uk>, Peter Oruba
> [    0.000000] microcode: microcode updated early to revision 0xd6, date =
> 2019-10-03
> [    6.035419] microcode: sig=0x406e3, pf=0x80, revision=0xd6
> [    6.035503] microcode: Microcode Update Driver: v2.01
> <tigran at aivazian.fsnet.co.uk>, Peter Oruba
> [   25.411983] microcode: updated to revision 0xdc, date = 2020-04-27
>
> dmesg-4.4.227-1.el7.elrepo.x86_64:
> [    0.052043] SRBDS: Vulnerable: No microcode
> [    0.052066] MDS: Vulnerable: Clear CPU buffers attempted, no microcode
> [    1.807176] microcode: CPU0 sig=0x406e3, pf=0x80, revision=0xc6
> [    1.807189] microcode: CPU1 sig=0x406e3, pf=0x80, revision=0xc6
> [    1.807210] microcode: CPU2 sig=0x406e3, pf=0x80, revision=0xc6
> [    1.807230] microcode: CPU3 sig=0x406e3, pf=0x80, revision=0xc6
> [    1.807312] microcode: Microcode Update Driver: v2.01
> <tigran at aivazian.fsnet.co.uk>, Peter Oruba
>
> This leads me to believe that the microcode is not getting updated when
> using
> the elrepo lt kernel.  Is that expected?
>
> Thanks,
>
>    Orion
>

Looks like the explanation is in the posttrans scriptlet of microcode_ctl.

rpm -q --scripts microcode_ctl

[quote]
...
# For RPM selection, kernel flavours (like "debug" or "kdump" or "zfcp",
# with only the former being relevant to x86 architecture) are a part or RPM
# name; it's also a part of uname, with different separator used in RHEL 6/7
# and RHEL 8.  RT kernel, however, is special, as "rt" is another part
# of RPM name and it has its own versioning scheme both in NVR and uname.
# And there's the kernel package split in RHEL 8, so one should look for
*-core
# and not the main package.
pkgs="kernel kernel-debug kernel-rt kernel-rt-debug"
...
[/quote]

Therefore, initramfs will not be regenerated for kernel-ml or kernel-lt.

By the way, the microcode file name as shown by the lsinitrd command is:

kernel/x86/microcode/GenuineIntel.bin (Intel)

or

kernel/x86/microcode/AuthenticAMD.bin (AMD)

Akemi
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