On Wed, 11 Sep 2019 19:30:46 +0200
"Laszlo Ersek" <lersek@...> wrote:

On 09/10/19 17:58, Igor Mammedov wrote:

On Mon, 9 Sep 2019 21:15:44 +0200
Laszlo Ersek <lersek@...> wrote:

[...]

It looks like fwcfg smi feature negotiation isn't reusable in this case.
I'd prefer not to add another device just for another SMI feature
negotiation/activation.

I thought it could be a register on the new CPU hotplug controller that
we're going to need anyway (if I understand correctly, at least).

If we don't have to 'park' hotplugged CPUs, then I don't see a need for
an extra controller.

But:

How about stealing reserved register from pci-host similar to your
extended TSEG commit (2f295167 q35/mch: implement extended TSEG sizes)?
(Looking into spec can (ab)use 0x58 or 0x59 register)

Yes, that should work.

In fact, I had considered 0x58 / 0x59 when looking for unused registers
for extended TSEG configuration:

http://mid.mail-archive.com/d8802612-0b11-776f-b209-53bbdaf67515@redhat.com

So I'm OK with this, thank you.

Thanks for the tip!
... patches with a stolen register are on the way to mail-list.