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 3:30 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?

Thanks,
Feng

> 
> Thanks
> Kevin

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