[Xen-users] ucode=-1: did anybody have success?

[Sven Köhler <sven.koehler@xxxxxxxxx>]

Hi,

did anybody use Xen's ucode option successfully?
I'm trying to update the microcode before dom0 starts, since my dom0
doesn't have the xen microcode driver. I'm using a vanilla 3.12.x kernel
from kernel.org and to the best of my knowledge, the xen microcode
kernel driver didn't make it upstream yet, i.e., it's only in konrad's tree.

So I probably want ucode=-1. The documentation is speaking of a CPU
microcode update BLOB. So all I need is to make the microcode BLOB the
last module in grub, right? But: BLOB in which format?

Well, on my system the microcode exists in two formats:
- /lib/firmware/microcode.dat (not sure what the format is, it's
definitely not cpio based, as would be needed for ucode=scan)
- many single files in /lib/firmware/intel-ucode/


Which line in grub would be correct? I guess it isn't
  module /lib/firmware/microcode.dat
or
  module /lib/firmware/intel-ucode/<somefile>
by any chance?

Now the documentation of ucode goes one to talk to about some file
called kernel/x86/microcode/GenuineIntel.bin. But it only talks about it
in combination with ucode=scan. A wild guess could be, that this file is
identical to microcode.dat. Another wild guess could be, that this file
is something I have to download from intel, and this is also the file I
have to use as a module in case I'm using ucode=-1 instead of ucode=-1.

So could somebody who did all the research and experimenting show his
working configuration to me?

I think I tried microcode.dat once, and it didn't seem to work.
I haven't tried a file from /lib/firmware/intel-ucode/ as I only have
one production system and my test system is a VM where microcode updates
are not possible.


Regards,
  Sven


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