Re: [PATCH v2 for-5.2 3/5] ppc/xive: Introduce dedicated kvm_irqchip_in_kernel() wrappers

[Greg Kurz <groug@kaod.org>]

On Fri, 7 Aug 2020 09:15:54 +0200
Greg Kurz <groug@kaod.org> wrote:

> On Thu, 6 Aug 2020 19:55:29 +0200
> Cédric Le Goater <clg@kaod.org> wrote:
> 

[...]

> > > diff --git a/include/hw/ppc/xive.h b/include/hw/ppc/xive.h
> > > index 705cf48176fc..aa46e3fcf512 100644
> > > --- a/include/hw/ppc/xive.h
> > > +++ b/include/hw/ppc/xive.h
> > > @@ -161,6 +161,7 @@ typedef struct XiveNotifier XiveNotifier;
> > >  typedef struct XiveNotifierClass {
> > >      InterfaceClass parent;
> > >      void (*notify)(XiveNotifier *xn, uint32_t lisn);
> > > +    bool (*in_kernel)(const XiveNotifier *xn);
> > >  } XiveNotifierClass;
> > >  
> > >  /*
> > > @@ -396,6 +397,7 @@ typedef struct XivePresenterClass {
> > >                       uint8_t nvt_blk, uint32_t nvt_idx,
> > >                       bool cam_ignore, uint8_t priority,
> > >                       uint32_t logic_serv, XiveTCTXMatch *match);
> > > +    bool (*in_kernel)(const XivePresenter *xptr);
> > >  } XivePresenterClass;
> > >  
> > >  int xive_presenter_tctx_match(XivePresenter *xptr, XiveTCTX *tctx,
> > > 
> > > 
> > 
> > It seems redundant. Can we introduce a new XiveBackend QOM interface 
> > which would implement an in_kernel() handler ? and XiveRouter would 
> > inherit from it. 
> > 
> 
> Not sure to see how it would help... the XiveRouter type isn't used
> at the locations where we call kvm_irqchip_in_kernel(). Only
> XivePresenter and XiveNotifier...
> 

Looking again at xive_source_realize(), I now realize (forgive the pun ;) that
the negative check on kvm_irqchip_in_kernel() is a bit awkward. We usually
do more stuff when we have a KVM backend, not less. The intent seems to be
that the ESB MMIO should point to either I/O sub-region when XIVE is emulated
or to a mmapped subregion when XIVE is backed by a KVM device. This can be
achieved with a container and overlapping sub-regions (prio 0 for emulated,
prio 1 for KVM). And we no longer need to hijack XiveNotifier.

So in the end, we only need the method for XivePresenter.

I'll cook a v3.

> > C.
> > 
> > 
> > 
> > 
> > 
>