[ovirt-devel] rethinking fake-kvm and faqemu

[Martin Polednik]

Hello everyone,

I've been reworking the fake_kvm and faqemu VDSM hook to make them
somewhat more usable and mostly to allow testing of ppc64le on x86_64
based hosts.

TL;DR version: checkout [1], enable fake_kvm and happy ppc64le hacking :)

Current fake_kvm isn't really a hook and is contained within 'caps'
module. This is wrong for multiple reasons, the most important one
being mixing optional with mainline code. Another issue appears when
one tries to move the fake_kvm code into a hook: the whole notion of
architectures within VDSM is contained within the 'caps' module.

The patch series, which git tip is at [1], introduces new cpuinfo
module that moves information related to architecture to 'cpuinfo'
module of the VDSM library. Intermediate benefit is that current hooks
and library code can access the information related to host's cpu.

This allows for moving fake_kvm code into a hook that I've called
fakearch. Fakearch is, in my opinion, more suitable name - there is
barely any KVM faking, but the host 'fakes' selected architecture.

Faqemu is, on the other hand, a hook. Unfortunately it wasn't really
updated and doesn't allow running VMs under fake architecture. The
series therefore try to refactor it to allow cross-arch VMs to be
started (the VM actually uses host architecture, but from engine's
point of view it's running on the faked arch).

So far tested cross-arch runs are 
* x86_64->x86_64 (faqemu functionality),
* x86_64->ppc64le (the most important one),
* ppc64le->x86_64,
* ppc64le->ppc64le (faqemu for Power).

I'm interested in your reviews and comments regarding this effort!

[1] https://gerrit.ovirt.org/#/c/46962/

Best regards,
mpolednik