Re: [Qemu-ppc] [PATCH] spapr/xive: H_INT_ESB is used for LSIs only

[David Gibson]

On Fri, Jun 21, 2019 at 05:05:45PM +0200, Cédric Le Goater wrote:
> On 21/06/2019 16:52, Greg Kurz wrote:
> > As indicated in the function header, this "hcall is only supported for
> > LISNs that have the ESB hcall flag set to 1 when returned from hcall()
> > H_INT_GET_SOURCE_INFO". We only set that flag for LSIs actually.
> > 
> > Check that in h_int_esb().
> 
> Indeed. H_INT_ESB should work on any IRQ, but I think it's better 
> to check that the HCALL is only used with the IRQ requiring it.

I'm not so convinced.  It seems to me that specifically limiting this
to certain things limits our options if we ever need future
workarounds for problems with ESB mapping.

In addition using H_INT_ESB for non-LSIs could be useful for minimal
guests (e.g. kvm-unit-tests) where mapping memory might be awkward.

So, I'm not really seeing a compelling reason to apply this.

> 
> > Signed-off-by: Greg Kurz <address@hidden>
> 
> Reviewed-by: Cédric Le Goater <address@hidden>
> 
> Thanks,
> 
> C.
> 
> > ---
> >  hw/intc/spapr_xive.c |    6 ++++++
> >  1 file changed, 6 insertions(+)
> > 
> > diff --git a/hw/intc/spapr_xive.c b/hw/intc/spapr_xive.c
> > index 58c2e5d890bd..01dd47ad5b02 100644
> > --- a/hw/intc/spapr_xive.c
> > +++ b/hw/intc/spapr_xive.c
> > @@ -1408,6 +1408,12 @@ static target_ulong h_int_esb(PowerPCCPU *cpu,
> >          return H_P2;
> >      }
> >  
> > +    if (!xive_source_irq_is_lsi(xsrc, lisn)) {
> > +        qemu_log_mask(LOG_GUEST_ERROR, "XIVE: LISN " TARGET_FMT_lx "isn't 
> > LSI\n",
> > +                      lisn);
> > +        return H_P2;
> > +    }
> > +
> >      if (offset > (1ull << xsrc->esb_shift)) {
> >          return H_P3;
> >      }
> > 
> 

-- 
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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