Re: [Xen-devel] [PATCH v4 05/17] xen/arm: ITS: implement hw_irq_controller for LPIs

[Vijay Kilari <vijay.kilari@xxxxxxxxx>]

On Wed, Jul 15, 2015 at 3:02 PM, Ian Campbell <ian.campbell@xxxxxxxxxx> wrote:
> On Wed, 2015-07-15 at 10:26 +0200, Julien Grall wrote:
>
>> >>> @@ -149,7 +173,7 @@ int gic_route_irq_to_guest(struct domain *d, unsigned
>> >>> int virq,
>> >>>             test_bit(GIC_IRQ_GUEST_ENABLED, &p->status) )
>> >>>            goto out;
>> >>>
>> >>> -    desc->handler = gic_hw_ops->gic_guest_irq_type;
>> >>> +    desc->handler = get_guest_hw_irq_controller(desc->irq);
>> >>>        set_bit(_IRQ_GUEST, &desc->status);
>> >>>
>> >>>        gic_set_irq_properties(desc, cpumask_of(v_target->processor),
>> >>> priority);
>> >>> diff --git a/xen/arch/arm/irq.c b/xen/arch/arm/irq.c
>> >>> index 2dd43ee..ba8528a 100644
>> >>> --- a/xen/arch/arm/irq.c
>> >>> +++ b/xen/arch/arm/irq.c
>> >>> @@ -35,7 +35,13 @@ static DEFINE_SPINLOCK(local_irqs_type_lock);
>> >>>    struct irq_guest
>> >>>    {
>> >>>        struct domain *d;
>> >>> -    unsigned int virq;
>> >>> +    union
>> >>> +    {
>> >>> +        /* virq refer to virtual irq in case of spi */
>> >>> +        unsigned int virq;
>> >>> +        /* virq refer to event ID in case of lpi */
>> >>> +        unsigned int vid;
>> >>
>> >>
>> >> Why can't we store the event ID in the irq_guest? As said on v3, this is 
>> >> not
>> >
>> > Are you referring to irq_desc in above statement?
>>
>> Yes sorry.
>
> I'm afraid I don't follow your suggestion here, are you suggesting that
> the vid field added above should be moved to irq_desc?
>
> But the vid _is_ domain specific, it is the virtual event ID which is
> per-domain (it's the thing looked up in the ITT to get a vLPI to be
> injected). I think it is a pretty direct analogue of the virq field used
> for non-LPI irq_guest structs.
>
> If we had need for the physical event id then that would like belong in
> the irq_desc.
>
> Your proposal on v3 looks to be around moving the its_device pointer to
> the irq_desc, which appears to have been done here, along with turning
> the virq+vid into a union as requested there too.
>
>> >> It has been suggested by Ian to move col_id in the its_device in the
>> >> previous version [4]. Any reason to not doing it?
>> >
>> > In round robin fashion each plpi is attached to col_id. So storing
>> > in its_device is not possible. In linux latest col_id is stored in 
>> > its_device
>> > structure for which set_affinity is called.
>
> Are you saying that in Linux all Events/LPIs associated with a given ITS
> device are routed to the same collection?

 Not associated with same collection. Events are associated with cpu
for which cpu_mask is set and the collection id of that cpu is stored
in the its_device, which is later used for SYNC. So effectively it_device
does not store collection id associated for all Events of that device.

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