Re: [RFC 3/3] x68: acpi: trigger SMI before scanning for hotplugged CPUs

[Igor Mammedov]

On Tue, 14 Jul 2020 14:28:29 +0200
Laszlo Ersek <lersek@redhat.com> wrote:

> (CC'ing Peter Krempa due to virsh setvcpu (singular) / setvcpus (plural)
> references)
> 
> On 07/10/20 18:17, Igor Mammedov wrote:
[...]

> (3) Just a thought: I wonder if we should reserve both ports (0xB2 and
> 0xB3 too). For now we don't have any use for the "data" port, but
> arguably it's part of the same register block.

we probably should, might be used for unplug part.

BTW any ideas how we'd like to procceed with unplug?

current flow looks like:

QEMU                       OSPM
unplug_req()
1)   =>SCI     --->
  -------------------------
2)                   handle_sci()
                         scan for events and send
                             Notify per removed CPU
                             clear rm_evt
  -------------------------
3)                   offline cpu
  -------------------------
4)                    call _EJ0 to unplug CPU
                         write into ej_evt
              <-------------
  -------------------------
5)  unplug cb
 

We probably should modify _EJ0 to send SMI instead of direct access
to cpuhp block, the question is how OSPM would tell FW which CPU it
ejects.
                      

[...]