Re: [Xen-devel] [PATCH v6 10/31] xen/arm: ITS: Introduce gic_is_lpi helper function

[Vijay Kilari <vijay.kilari@xxxxxxxxx>]

On Mon, Aug 31, 2015 at 10:19 PM, Julien Grall <julien.grall@xxxxxxxxxx> wrote:
> Hi Vijay,
>
> On 31/08/2015 12:06, vijay.kilari@xxxxxxxxx wrote:
>>
>> diff --git a/xen/arch/arm/gic.c b/xen/arch/arm/gic.c
>> index 758678d..2199963 100644
>> --- a/xen/arch/arm/gic.c
>> +++ b/xen/arch/arm/gic.c
>> @@ -62,6 +62,15 @@ enum gic_version gic_hw_version(void)
>>      return gic_hw_ops->info->hw_version;
>>   }
>>
>> +#ifdef HAS_GICV3
>> +bool_t gic_is_lpi(unsigned int irq)
>> +{
>> +    return (irq >= FIRST_GIC_LPI && irq < (1 <<
>> gic_hw_ops->info->nr_id_bits));
>
>
> It would make more sense to calculate the number of ID supported at boot
> time rather than re-calculate everytime this function is called (i.e very
> often).
>
>> +}
>> +#else
>> +bool_t gic_is_lpi(unsigned int irq) { return 0; }
>> +#endif
>
>
> I though I'd already say it on a previous version. I would like to avoid
> seen any #ifdef HAS_GICV3 in the generic code include interrupt framework.
>
> In this case, I don't see much the benefit to do a specific case for
> platform not using GICv3 (i.e ARM32).

You mean, let gic_is_lpi() implemented for both ARM64/32 and let this
function fail
always for ARM32?

Other option is to implement callback to hw drivers (gicv3 and gicv2).
But overhead of callback
should also be considered

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