Re: [Xen-devel] [PATCH v9 11/17] vt-d: Add API to update IRTE when VT-d PI is used

["Tian, Kevin" <kevin.tian@xxxxxxxxx>]

> From: Jan Beulich [mailto:JBeulich@xxxxxxxx]
> Sent: Tuesday, November 24, 2015 4:52 PM
> 
> >>> On 24.11.15 at 08:56, <kevin.tian@xxxxxxxxx> wrote:
> >>  From: Wu, Feng
> >> Sent: Tuesday, November 24, 2015 3:54 PM
> >> > From: Tian, Kevin
> >> > Sent: Tuesday, November 24, 2015 3:45 PM
> >> > > +    /* Setup/Update interrupt remapping table entry. */
> >> > > +    setup_posted_irte(&new_ire, &old_ire, pi_desc, gvec);
> >> > > +    ret = cmpxchg16b(p, &old_ire, &new_ire);
> >> > > +
> >> > > +    /*
> >> > > +     * In the above, we use cmpxchg16 to atomically update the 128-bit
> >> > IRTE,
> >> > > +     * and the hardware cannot update the IRTE behind us, so the 
> >> > > return
> >> > value
> >> >
> >> > hardware can DEFINITELY update IRTE behind us, right? e.g. after the IRTE
> >> > entry
> >> > is fully up, when interrupt is posted, etc. Here you might mean hardware
> >> > cannot
> >> > update the IRTE at this point?
> >>
> >> Yes, you description above is more accurate. But why hardware needs to
> >> update IRTE when interrupt is posted? I think it needs to update the
> >> posted interrupt descriptor when posting an interrupt, not the IRTE,
> >> right?
> >
> > sorry mess IRTE and posted descriptor together. but using "behind"
> > is still not accurate to state your point here. :-)
> 
> Well, "behind us" and "behind our back" seem to mean mostly the
> same to me.
> 

Thanks for confirming language part. Then I'm OK with it.

Thanks
Kevin

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