Re: [Xen-devel] [PATCH RFC 0/8] libxl, xl, public/io: PV backends feature control

[Roger Pau Monné <roger.pau@xxxxxxxxxx>]

On Wed, Feb 07, 2018 at 12:20:42PM +0100, Juergen Gross wrote:
> On 07/02/18 12:16, Roger Pau Monné wrote:
> > On Thu, Nov 02, 2017 at 06:06:08PM +0000, Joao Martins wrote:
> >> * Toolstack constructs a key value store of features, and user specifies 
> >> those
> >> through special entry names prefixed also as "require". Toolstack is 
> >> stateless thus sys
> >> admin has full control over what to pass to the backend. In other words it
> >> doesn't look at particular feature names/values.
> >>
> >> * The backend will then use that for seeding its maximum feature set to the
> >> frontend.
> > 
> > Oh, I see. So the backend picks up the suggested config from this
> > directory together with it's capabilities and then produces the final
> > set of features exposed to the frontend.
> > 
> > In order to prevent adding more logic to the backends, would it make
> > sense to export the backend capabilities in /sys/ (or sysctl on BSDs)
> > and do those calculations from the toolstack itself, so that the
> > toolstack directly writes the features to the backend top level
> > xenstore directory?
> 
> So you want the toolstack to read the /sys/ entries? How would that work
> for driver domains?

Right, that won't work for driver domains... And feeding that
information from a driver domain into the control domain is even
worse, so I'm fine with this.

Roger.

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