Re: [Xen-devel] [PATCH v9 08/17] vmx: Suppress posting interrupts when 'SN' is set

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

> -----Original Message-----
> From: Tian, Kevin
> Sent: Tuesday, November 24, 2015 3:53 PM
> To: Wu, Feng <feng.wu@xxxxxxxxx>; xen-devel@xxxxxxxxxxxxx
> Cc: Keir Fraser <keir@xxxxxxx>; Jan Beulich <jbeulich@xxxxxxxx>; Andrew
> Cooper <andrew.cooper3@xxxxxxxxxx>
> Subject: RE: [PATCH v9 08/17] vmx: Suppress posting interrupts when 'SN' is
> set
> 
> > From: Wu, Feng
> > Sent: Tuesday, November 24, 2015 3:47 PM
> >
> >
> > > -----Original Message-----
> > > From: Tian, Kevin
> > > Sent: Tuesday, November 24, 2015 3:30 PM
> > > To: Wu, Feng <feng.wu@xxxxxxxxx>; xen-devel@xxxxxxxxxxxxx
> > > Cc: Keir Fraser <keir@xxxxxxx>; Jan Beulich <jbeulich@xxxxxxxx>;
> Andrew
> > > Cooper <andrew.cooper3@xxxxxxxxxx>
> > > Subject: RE: [PATCH v9 08/17] vmx: Suppress posting interrupts when 'SN'
> is
> > > set
> > >
> > > > From: Wu, Feng
> > > > Sent: Tuesday, November 03, 2015 4:43 PM
> > > N' is set
> > > >
> > > > Currently, we don't support urgent interrupt, all interrupts
> > > > are recognized as non-urgent interrupt, so we cannot send
> > > > posted-interrupt when 'SN' is set.
> > > >
> > > > CC: Kevin Tian <kevin.tian@xxxxxxxxx>
> > > > CC: Keir Fraser <keir@xxxxxxx>
> > > > CC: Jan Beulich <jbeulich@xxxxxxxx>
> > > > CC: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
> > > > Signed-off-by: Feng Wu <feng.wu@xxxxxxxxx>
> > > > Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx>
> > > > Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
> > >
> > > Acked-by: Kevin Tian <kevin.tian@xxxxxxxxx>, with one small comment:
> > >
> > > > +        do {
> > > > +            /*
> > > > +             * Currently, we don't support urgent interrupt, all
> > > > +             * interrupts are recognized as non-urgent interrupt,
> > > > +             * so we cannot send posted-interrupt when 'SN' is set.
> > > > +             * Besides that, if 'ON' is already set, we cannot set
> > > > +             * posted-interrupts as well.
> > > > +             */
> > >
> > > Is above comment accurate. "cannot set" is too strong for 'ON'
> > > already set, right? Ideally there's no correctness issue if you
> > > still deliver another posted-interrupt even when ON is already set.
> > > To me it's more like an optimization then it's cleaner to say
> > > "we can avoid"...
> >
> > Here, we just emulate the hardware's behavior, in hardware p.o.v,
> > if 'ON' is set, the notification event will not be delivered, so here
> > I try to follow the hardware, is this reasonable for you?
> >
> 
> I understand it's hardware behavior, just thought whether the comment
> is too strong. Could we rephrase it as "Besides that, if 'ON' is already
> set, no need to set posted-interrupts as well, according to hardware
> behavior"?

Sure, that should be great! Thanks a lot:)

Thanks,
Feng

> 
> Thanks
> Kevin

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