Re: [Xen-devel] [Draft F] Xen on ARM vITS Handling

[Julien Grall <julien.grall.oss@xxxxxxxxx>]

On 12/06/2015 09:32, Julien Grall wrote:
> On 12/06/2015 09:16, Ian Campbell wrote:
> > On Fri, 2015-06-12 at 09:09 -0400, Julien Grall wrote:
> > > Hi Ian,
> > >
> > > On 12/06/2015 04:52, Ian Campbell wrote:
> > > > On Fri, 2015-06-12 at 14:07 +0530, Vijay Kilari wrote:
> > > > So pLPIs must be routed at device assignment time because in the vLPI
> > > > configuration table trap there is no mapping back to a single pLPI.
> > > I just remembered the exact reason that made use to differ SPI enabling.
> > I can't parse this sentence, differ how?
> deferring sorry.
>
> > > When the device is assigned, the domain VCPUs are still down (even
> > > VCPU0).
> > >
> > > If we receive an interrupt before the VCPU0 is unpaused, the interrupt
> > > will be lost. Same if the interrupt is not yet configured (i.e before
> > > the vITS setup correctly the table) with your proposal.
> > Is this any different to booting with the ITT not setup?
> I don't understand your question.
>
> > (SPIs are a slightly different case because they don't need h/w routing)
> I think you mixed PPIs with SPIs. SPIs (shared private interrupt)
s/private/processor/

> requires h/w routing.
>
> > > This could happen when the device is not quiescent. We had this issue on
> > > the vexpress at boot time when the network card was trying to send an
> > > interrupt before DOM0 is setup.
> > I don't fully understand the issue you are trying to describe, but do
> > you want to propose a change to the spec?
> I actually don't know how to modify it. So it's an open question.
>
> vgic_vcpu_inject_irq doesn't queue the interrupt if a VCPU is down. I
> think this is because the state of the VCPU wouldn't be correct.
>
> The process would be something like:
>
>      - Creation of the domain
>      => All vCPUs are down
>
>      - Device is assigned to the guest
>          => Enable physical LPIs
>
>      * physical LPI is received *
>      => Will be ignored and not EOIed (VCPU0 is down)
>          => The LPI will never fired again during the guest life
>
>      -  Domain is started by the toolstack
>           => VCPU0 is online
>
> Regards,
--
Julien Grall

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