Re: [Qemu-devel] [PATCH 07/11] spapr: add hotplug interrupt machine options

[Bharata B Rao]

On Fri, Oct 14, 2016 at 01:04:37PM -0500, Michael Roth wrote:
> Quoting Bharata B Rao (2016-10-14 03:37:32)
> > On Wed, Oct 12, 2016 at 06:13:55PM -0500, Michael Roth wrote:
> > > This adds machine options of the form:
> > > 
> > >   -machine pseries,legacy-hotplug-events=true
> > >   -machine pseries,legacy-hotplug-events=false
> > > 
> > > to denote whether or not we wish to force the use of "legacy" style
> > > hotplug events, which are surfaced through EPOW interrupts instead of
> > > a dedicated interrupt source, and lack certain features necessary,
> > > mainly, for memory unplug support.
> > > 
> > > If false, QEMU will default to "legacy" style unless the guest
> > > advertises support for the newer events via
> > > ibm,client-architecture-support hcall during early boot.
> > > 
> > > For pseries-2.7 and earlier we default to true, for newer machine
> > > types we default to false.
> > > 
> > > Signed-off-by: Michael Roth <address@hidden>
> > > ---
> > >  hw/ppc/spapr.c              | 31 +++++++++++++++++++++++++++++++
> > >  include/hw/ppc/spapr.h      |  1 +
> > >  include/hw/ppc/spapr_ovec.h |  1 +
> > >  3 files changed, 33 insertions(+)
> > > 
> > > diff --git a/hw/ppc/spapr.c b/hw/ppc/spapr.c
> > > index f8cde92..d80a6fa 100644
> > > --- a/hw/ppc/spapr.c
> > > +++ b/hw/ppc/spapr.c
> > > @@ -1816,6 +1816,11 @@ static void ppc_spapr_init(MachineState *machine)
> > > 
> > >      spapr_ovec_set(spapr->ov5, OV5_FORM1_AFFINITY);
> > > 
> > > +    /* use dedicated HP event source if guest supports it */
> > > +    if (spapr->use_hotplug_event_source) {
> > > +        spapr_ovec_set(spapr->ov5, OV5_HP_EVT);
> > 
> > The above comment can be confusing. Here you really mean that
> > the machine type version supports OV5_HP_EVT right ? Because
> > guest support for the same is determined during cas call later.
> 
> What trying to get it across that support would only be enabled if the
> guest indicates support for it later. What about something like:
> 
> /* advertise support for dedicated HP event source to guests */

Sounds good. Thanks.

> > 
> > Regards,
> > Bharata.