Re: [Xen-devel] Feature control on PV devices

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Fri, Sep 15, 2017 at 01:34:49PM +0200, Juergen Gross wrote:
> >>>>
> >>>> Backends reads and seeds with (and assuming it passes backend validation 
> >>>> ofc):
> >>>>
> >>>> /local/domain/0/backend/vif/8/0/multi-queue-max-queues = 2
> >>>> /local/domain/0/backend/vbd/8/51713/multi-queue-max-queues = 2
> >>>> /local/domain/0/backend/vbd/8/51713/max-ring-page-order = 0
> >>>>
> >>>> The XL configuration entry for controlling these tunable are just 
> >>>> examples it's
> >>>> not clear the general preference for this. An alternative could be:
> >>>>
> >>>> vif = ["bridge=br0,features=queues:2\\;max-ring-page-order:0"]
> >>>>
> >>>> Which lets us have more generic feature control, without sticking to 
> >>>> particular
> >>>> features names.
> >>>>
> >>
> >> In case the above was about config format, this one suggested above sounds 
> >> more
> >> general, and easy to reuse across backends. Maybe instead of "features", 
> >> could
> >> be "backend_features" since, most PV backends declare a "backend" and a
> >> "backend_id" as per libxl IDL.
> >>
> > 
> > The proposed syntax looks a bit difficult to parse.
> > 
> > What's wrong with request-XXX=YYY syntax? We can have many of those as
> > we like. Xl just picks those and concatenate them into backend_features.
> 
> Is it possible to parse those without having to know about individual
> XXX values? Otherwise we'd be able to support only features known by xl
> instead of those known by the various backends.
> 

Xl sees a list of key-value pairs. If the key of a pair starts with the
predefined prefix, xl (eventually) passes the pair on to backend. I
don't think knowing individual XXX value is needed or desired.

_______________________________________________
Xen-devel mailing list
Xen-devel@xxxxxxxxxxxxx
https://lists.xen.org/xen-devel