Re: [qemu-s390x] [Qemu-devel] [PATCH v3 6/7] s390x/kvm: handle AP instruction interception

[Halil Pasic]

On 04/06/2018 02:09 PM, Halil Pasic wrote:
> Yes it is conceptually ugly. I'm 100% with you. That's why it should go
> away soon. From the practicality perspective however I would even argue that 
> it's
> helpful to the user: tells 'oops you have forgotten something'. IMHO
> it's a shortcut of type make the problem smaller. Regarding what is
> harder and what is easier: the author is probably the most fit to decide
> that. If it is harder, it makes no sense, as this is all about cutting
> corners.

I've just realized, I have overlooked something. And that is using
what libvirt calls host-model and host-passthrough mode. There the
user does not explicitly ask for ap=on. So the user would get slapped
in the face by this 'needs vfio-ap device' message (AFAIU) after
upgrading stuff (without even knowing that AP was added) which is
extremely ugly! I need to think about this some more.