On Tue, Nov 27, 2018 at 08:30:15AM +0100, Cédric Le Goater wrote: > On 11/27/18 1:11 AM, David Gibson wrote: > > On Mon, Nov 26, 2018 at 10:39:44AM +0100, Cédric Le Goater wrote: > >> On 11/26/18 6:44 AM, David Gibson wrote: > >>> On Fri, Nov 23, 2018 at 11:28:24AM +0100, Cédric Le Goater wrote: > >>>> On 11/23/18 2:10 AM, David Gibson wrote: > >>>>> On Thu, Nov 22, 2018 at 05:50:07PM +1100, Benjamin Herrenschmidt wrote: > >>>>>> On Thu, 2018-11-22 at 15:44 +1100, David Gibson wrote: > >>>>>>> > >>>>>>> Sorry, didn't think of this in my first reply. > >>>>>>> > >>>>>>> 1) Does the hardware ever actually write back to the EAS? I know it > >>>>>>> does for the END, but it's not clear why it would need to for the > >>>>>>> EAS. If not, we don't need the setter. > >>>>>> > >>>>>> Nope, though the PAPR model will via hcalls > >>>>> > >>>>> Right, bit AIUI the set_eas hook is about abstracting PAPR vs bare > >>>>> metal details. Since the hcall knows it's PAPR it can just update the > >>>>> backing information for the EAS directly, and no need for an > >>>>> abstracted hook. > >>>> > >>>> Indeed, the first versions of the XIVE patchset did not use such hooks, > >>>> but when discussed we said we wanted abstract methods for the router > >>>> to validate the overall XIVE model, which is useful for PowerNV. > >>>> > >>>> We can change again and have the hcalls get/set directly in the EAT > >>>> and ENDT. It would certainly simplify the sPAPR model. > >>> > >>> I think that's the better approach. > >> > >> ok. let's keep that in mind for : > >> > >> [PATCH v5 11/36] spapr/xive: use the VCPU id as a NVT identifier > >> [PATCH v5 16/36] spapr: add hcalls support for the XIVE exploitation > >> > >> which are using the XiveRouter methods to access the controller EAT > >> and ENDT. I thought that was good practice to validate the model but > >> we can use direct sPAPR table accessors or none at all. > > > > Ok. Consistency is good as a general rule, but I don't think it makes > > sense to force the EAT and the ENDT into the same model. > > What do you mean by model ? the QEMU machine IC model ?
Oh, sorry, nothing that formal. By "model" I just meant the same
pattern of accessor hooks. They certainly do belong in the same qemu
object.
> > The EAT is
> > pure configuration, whereas the the ENDT has both configuration and
> > status. Or to look at it another way, the EAT is purely software
> > controlled, whereas the ENDT is at least partially hardware
> > controlled.
>
> yes but the EAT and the ENDT are XIVE internal tables of the same XIVE
> sub-engine, the IVRE, Interrupt Virtualization Routing Engine, formely
> known as VC, for Virtualization Controller. the EAS is just an entry
> point to the ENDT. I don't see why we would use different models for
> them.
>
> > (I realize that gets a bit fuzzy when considering PAPR, but I think
> > from the point of view of the XIVE model it makes sense to treat the
> > PAPR hypervisor logic as "software", even though it's "hardware" from the
> > guest point of view).
>
> That I agree but the resulting code is too ugly in the hcalls. Tell me
> when you reach patch 11, which links the machine IC model sPAPRXive to
> the generic XiveRouter and also check patch 16 introducing the hcalls,
> which update the XIVE internal tables.
>
> Thanks,
>
> C.
>
>
> >>
> >>
> >> I think these prereq patches could be merged now :
> >>
> >> [PATCH v5 12/36] spapr: initialize VSMT before initializing the IRQ
> >> [PATCH v5 13/36] spapr: introduce a spapr_irq_init() routine
> >> [PATCH v5 14/36] spapr: modify the irq backend 'init' method
> >>
> >> This one also :
> >>
> >> [PATCH v5 21/36] spapr: extend the sPAPR IRQ backend for XICS
> >>
> >> Thanks,
> >>
> >> C.
> >>
> >
>
--
David Gibson | I'll have my music baroque, and my code
david AT gibson.dropbear.id.au | minimalist, thank you. NOT _the_ _other_
| _way_ _around_!
http://www.ozlabs.org/~dgibson
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