Re: [Xen-devel] [RFC PATCH v3 07/18] xen/arm: ITS: implement hw_irq_controller for LPIs

[Vijay Kilari <vijay.kilari@xxxxxxxxx>]

On Tue, Jun 23, 2015 at 8:02 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> Hi Vijay,
>
> On 22/06/15 13:01, vijay.kilari@xxxxxxxxx wrote:
>> From: Vijaya Kumar K <Vijaya.Kumar@xxxxxxxxxxxxxxxxxx>
>>
>> Implements hw_irq_controller api's required
>> to handle LPI's
>
> This patch doesn't hw_irq_controller for LPI but just hack around the
> current GICv3 host hw_irq_controller.
>
> As said on the previous version, the goal of hw_irq_controller is too
> keep things simple (i.e few conditional code). Please introduce a
> separate hw_irq_controller for LPIs.

If new hw_irq_controller is introduced for LPIs, then this has to
be exported using some lpi structure which holds pointer to hw_irq_controller
for guest & host type similar to gic_hw_ops

>> +{
>> +    struct its_collection *col;
>> +    struct its_device *its_dev = get_irq_device(desc);
>> +    u8 *cfg;
>> +    u32 virq = irq_to_virq(desc);
>> +
>> +    ASSERT(virq < its_dev->nr_lpis);
>> +
>> +    cfg = gic_rdists->prop_page + desc->irq - NR_GIC_LPI;
>> +    if ( enable )
>> +        *cfg |= LPI_PROP_ENABLED;
>> +    else
>> +        *cfg &= ~LPI_PROP_ENABLED;
>> +
>> +    /*
>> +     * Make the above write visible to the redistributors.
>> +     * And yes, we're flushing exactly: One. Single. Byte.
>> +     * Humpf...
>> +     */
>> +    if ( gic_rdists->flags & RDIST_FLAGS_PROPBASE_NEEDS_FLUSHING )
>> +        clean_and_invalidate_dcache_va_range(cfg, sizeof(*cfg));
>> +    else
>> +        dsb(ishst);
>> +
>> +    /* Get collection id for this event id */
>> +    col = &its_dev->its->collections[virq % num_online_cpus()];
>
> This is fragile, you are assuming that num_online_cpus() will never
> change. Why don't you store the collection in every irq_desc?

  This will add additional 8 bytes overhead for each irq_desc.

Also is there a macro to get number of actual number processors in system.?
AUI, nr_cpu_ids always returns 128

Regards
Vijay

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