Re: [PATCH v5] xen: introduce CONFIG_HAS_SHARED_INFO for archs without a shared page

[Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>]

On 7/8/26 12:52 PM, Jan Beulich wrote:
> > +#ifndef CONFIG_HAS_SHARED_INFO
> > +/*
> > + * Placeholder ops for domains with neither a shared_info page nor (yet)
> > + * a FIFO control block.  None of these are ever reachable in practice;
> > + * they only exist to keep d->evtchn_port_ops non-NULL.
> > + */
> > +static void cf_check evtchn_none_set_pending(
> > +    struct vcpu *v, struct evtchn *evtchn) {}
> > +static void cf_check evtchn_none_noop(
> > +    struct domain *d, struct evtchn *evtchn) {}
> > +static bool cf_check evtchn_none_false(
> > +    const struct domain *d, const struct evtchn *evtchn) { return false; }
> > +static void cf_check evtchn_none_print_state(
> > +    struct domain *d, const struct evtchn *evtchn) {}
> > +
> > +static const struct evtchn_port_ops evtchn_port_ops_none = {
> > +    .set_pending   = evtchn_none_set_pending,
> > +    .clear_pending = evtchn_none_noop,
> > +    .unmask        = evtchn_none_noop,
> > +    .is_pending    = evtchn_none_false,
> > +    .is_masked     = evtchn_none_false,
> > +    .print_state   = evtchn_none_print_state,
> > +};
> > +
> > +void evtchn_none_init(struct domain *d)
> > +{
> > +    d->evtchn_port_ops = &evtchn_port_ops_none;
> > +}
> > +#endif /* !CONFIG_HAS_SHARED_INFO */
> ... we wondering whether any of this is needed when FIFO is available. In
> v4 all that was noticed was that SHARED_INFO=n together with EVTCHN_FIFO=n
> is a problem. And having fewer cf_check functions in the build is always a
> win (I think).
I thought an opposite that it is good to have cf_check when pointer to 
function is used. So why we have to make an exception in this case?
~ Oleksii