Re: [Qemu-devel] [Xen-devel] [PATCH 3/4] xen: introduce an event channel for buffered io event notifications

[Stefano Stabellini]

On Tue, 15 Nov 2011, Ian Campbell wrote:
> > +    xc_get_hvm_param(xen_xc, xen_domid, HVM_PARAM_BUFIOREQ_EVTCHN,
> > +            &bufioreq_evtchn);
> > +    rc = xc_evtchn_bind_interdomain(state->xce_handle, xen_domid,
> > +            (uint32_t)bufioreq_evtchn);
> > +    if (rc == -1) {
> > +        fprintf(stderr, "bind interdomain ioctl error %d\n", errno);
> > +        return -1;
> > +    }
> > +    state->bufioreq_local_port = rc;
> 
> Does this fallback gracefully on hypervisors which don't have this new
> hvm param? It doesn't look like it but perhaps I'm missing something.

No, it does not.
However upstream Qemu doesn't work very well with Xen 4.1 anyway, the
first Xen release that is going to support it will be Xen 4.2 that
should have this feature.