[libvirt] [PATCH 0/5] qemu: Detect KVM usability correctly

[Andrea Bolognani]

On Fri, 2018-09-14 at 16:35 +0200, Jiri Denemark wrote:
> On Fri, Sep 14, 2018 at 15:36:42 +0200, Andrea Bolognani wrote:
> > How ridiculous would it be to invalidate capabilities whenever
> > the daemon is restarted? That might strike a somewhat reasonable
> > balance between requiring the admin to delete a bunch of internal
> > files after configuring the system to load the KVM module and
> > re-probing QEMU all the time.
> 
> This would effectively revert the addition of on-disk cache, which was
> introduced with a very good reason. Starting libvirtd with a lot of QEMU
> binaries would take a very long time without the persistent cache. Also
> libguestfs running libvirt in session mode would get crazy about it. In
> other words, invalidating capabilities cache whenever libvirtd is
> started is not acceptable.

Fair enough!

[...]
> > > After removing this capability it looks like virQEMUCapsIsValid will
> > > always invalidate every single non-native QEMU binary since kvm could
> > > not clearly be used when probing and /dev/kvm is present. Shouldn't we
> > > add a check which makes sure we don't go this far for non-native
> > > binaries?
> > 
> > We can use virQEMUCapsGuestIsNative() and skip all KVM-related
> > checks for non-native binaries. Does that sound okay?
> 
> Yeah, I think that should work.

I just posted a 6/5 that does just that.

-- 
Andrea Bolognani / Red Hat / Virtualization