Re: [Xen-devel] [PATCH v6 13/18] Update IRTE according to guest interrupt config changes

["Wu, Feng" <feng.wu@xxxxxxxxx>]

> -----Original Message-----
> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Monday, September 07, 2015 7:03 PM
> To: Wu, Feng
> Cc: xen-devel@xxxxxxxxxxxxx
> Subject: RE: [PATCH v6 13/18] Update IRTE according to guest interrupt config
> changes
> 
> >>> On 06.09.15 at 06:54, <feng.wu@xxxxxxxxx> wrote:
> >> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> >> Sent: Friday, September 04, 2015 11:59 PM
> >> >>> On 25.08.15 at 03:57, <feng.wu@xxxxxxxxx> wrote:
> >>> 
> >> > +            if ( vcpu )
> >> > +            {
> >> > +                rc = pi_update_irte( vcpu, info,
> pirq_dpci->gmsi.gvec );
> >> > +                if ( unlikely(rc) )
> >> > +                    dprintk(XENLOG_G_INFO,
> >> > +                            "%pv: failed to update PI IRTE,
> >> gvec:%02x\n",
> >> > +                            vcpu, pirq_dpci->gmsi.gvec);
> >>
> >> Even if only a debug build printk() - aren't you afraid that if this
> >> ever triggers, it will trigger a lot? And hence be pretty useless?
> >
> > I think it reaches this debug printk rarely, but a least, when it is really
> > failed, it
> > can give people some hints about why we are using interrupt remapping
> > instead
> > of interrupt posing for the external interrupts.
> 
> I understand your motivation, but you don't really answer my
> question. (And btw., if you really mean "rarely", then there's a bug
> somewhere that you need to fix. It should _never_ trigger if
> everything is working correctly.)

I mean pi_update_irte() can return failure theoretically, because there
are some pointer check in it. You said, it would trigger a lot if this ever
triggers. Do you mean for a specific pirq, it will always fail after the first
failure? So what is your suggestion here? Adding an ASSERT()?

Thanks,
Feng

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