Re: [Xen-devel] [PATCH v5 12/22] xen/arm: ITS: Add GICR register emulation

[Julien Grall <julien.grall@xxxxxxxxxx>]

On 04/08/2015 07:55, Vijay Kilari wrote:
> > > > > > What would happen if the LPI is injected before the GICR_PROPBASER is
> > > > > > enabled? See for more details on the problem here [1]
> > > > >   Check is required before accessing LPI property table if property
> > > > > table is available
> > > > > or not?.
> > > > You didn't answer to my question... What would you do if the property is
> > > > not available? Ignoring the LPI? Would the LPI can fire back after the
> > > > property table is set and the LPI enabled?
> > >     Same as above solution.  Ignore LPI as we don't have LPI property
> > > information to inject.
> > That still not answering to my question. What happen if we ignore the
> > LPI? Would the device resend the MSI and therefore the LPI later? If
> > not, how do you plan to handle this?
>    LPIs are edge triggered, so device won't raise again.
>
> We can put in inflight and wait for guest to enabled it, But we are not sure
> when LPI property table will be set for this vLPI. On GICR_PROPBASER update
> with new property table, we parse the LPI property table and call
> vits_{enable/disable}_lpi
If we don't put it inflight, we will surely loose some interrupt at some 
point if the device is not quiet before the guest has booted and/or 
setup the device before enabling the LPI.
> > With the LPI implementation, it's valid to receive an LPI before the
> > guest effectively setup the ITS (i.e property table and the mapping to a
> > vLPI). This is because we enable to LPI as soon as we route it to the guest.
> >
> > Regards,
> >
> > --
> > Julien Grall
[1] 
http://lists.xenproject.org/archives/html/xen-devel/2015-06/msg02591.html
--
Julien Grall

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