Re: [Xen-users] How to patch cpu with xen

[Andy Smith <andy@xxxxxxxxxxxxxx>]

Hello,

On Mon, May 28, 2018 at 09:18:44AM +0200, Christoph wrote:
> is there any step by step howto for patching cpu with xen/dom0?

On Debian I was able to do it by:

- Install intel-microcode or amd-microcode package from non-free
  repository. This rebuilds initramfs to have microcode concatenated
  on the end of it.

- Add "ucode=scan" to the hypervisor command line by editing
  /etc/default/grub to add that to the GRUB_CMDLINE_XEN variable.

- Run update-grub to rebuild /boot/grub/grub/cfg with the new
  command line argument.

- Reboot and if your loglvl is at info ("loglvl=info" in the
  hypervisor command line) you will see it patching the first CPU
  before dom0 loads:

  (XEN) microcode: CPU0 updated from revision 0xb00001d to 0xb00002c, date = 
2018-03-21

  and then after that every other CPU:

  (XEN) microcode: CPU2 updated from revision 0xb00001d to 0xb00002c, date = 
2018-03-21  
  (XEN) microcode: CPU4 updated from revision 0xb00001d to 0xb00002c, date = 
2018-03-21  
  (XEN) microcode: CPU6 updated from revision 0xb00001d to 0xb00002c, date = 
2018-03-21  
  (XEN) microcode: CPU8 updated from revision 0xb00001d to 0xb00002c, date = 
2018-03-21  
  (XEN) microcode: CPU10 updated from revision 0xb00001d to 0xb00002c, date = 
2018-03-21 
  (XEN) microcode: CPU12 updated from revision 0xb00001d to 0xb00002c, date = 
2018-03-21 
  (XEN) microcode: CPU14 updated from revision 0xb00001d to 0xb00002c, date = 
2018-03-21 
  (XEN) Brought up 16 CPUs

  If your loglvl isn't high enough (and "info" is not recommended
  for production) then you won't see any of that and will have to
  verify later by looking at /proc/cpuinfo.

Cheers,
Andy

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