Re: [PATCH v2 4/4] virtio-net: Add support for USO features

["Daniel P. Berrangé" <berrange@redhat.com>]

On Thu, Aug 01, 2024 at 11:50:40AM -0400, Michael S. Tsirkin wrote:
> On Thu, Aug 01, 2024 at 04:45:17PM +0100, Daniel P. Berrangé wrote:
> > So to ensure a QEMU is started with migration compatible features
> > will still require teaching libvirt about every single feature
> > that has a host kernel dependancy, so libvirt (or the app using
> > libvirt) knows to turn this off. This is alot more work for both
> > libvirt & the mgmt app, than having QEMU provide the generic
> > "platforms" concept which is extensible without needing further
> > work outside QEMU.
> 
> I am just not sure it can all amount to selecting from a list.
> For example, some resource can be limited on one host or another.
> Thus we get a number. Or there could be a set of N flags, with 2^N
> combinations.

We don't have to support all possible combinations IMHO. If a user
really does require precise control over every combination of some
settings, then exposing those tunables in libvirt is inevitable.

The platform concept only has to be able to express a "good enough"
subset of combinations, such that it is unlikely users will need to
have fine tuning for most of the tunables. We might end up exposing
a handful of tunables in libvirt anyway, but as long as we get the
common case satisifed, we'll eliminate most of the ongoing burden.

With regards,
Daniel
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