Re: [Xen-devel] [PATCH v3 29/39] ARM: new VGIC: Handle virtual IRQ allocation/reservation

[Andre Przywara <andre.przywara@xxxxxxx>]

Hi,

On 27/03/18 23:38, Stefano Stabellini wrote:
> On Wed, 21 Mar 2018, Andre Przywara wrote:
>> To find an unused virtual IRQ number Xen uses a scheme to track used
>> virtual IRQs.
>> Implement this interface in the new VGIC to make the Xen core/arch code
>> happy.
>> This is actually somewhat VGIC agnostic, so is mostly a copy of the code
>> from the old VGIC. But it has to live in the VGIC files, so we can't
>> easily reuse the existing implementation.
>>
>> Signed-off-by: Andre Przywara <andre.przywara@xxxxxxxxxx>
>> Acked-by: Julien Grall <julien.grall@xxxxxxx>
> 
> These are exactly identical to the existing functions. I wonder why we
> can't reuse them. In any case, I assume you know what you are doing from
> the code integration point of view :-)

They are, but there is no real shared VGIC code at the moment, and I
didn't want to introduce anything just for those simple functions,
especially with the prospect of the existing code going away anyway later.

> Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

Thanks!
Andre.

> 
> 
>> ---
>>  xen/arch/arm/vgic/vgic.c | 44 ++++++++++++++++++++++++++++++++++++++++++++
>>  1 file changed, 44 insertions(+)
>>
>> diff --git a/xen/arch/arm/vgic/vgic.c b/xen/arch/arm/vgic/vgic.c
>> index 3d818a98ad..8aaad4bffa 100644
>> --- a/xen/arch/arm/vgic/vgic.c
>> +++ b/xen/arch/arm/vgic/vgic.c
>> @@ -722,6 +722,50 @@ bool vgic_evtchn_irq_pending(struct vcpu *v)
>>      return pending;
>>  }
>>  
>> +bool vgic_reserve_virq(struct domain *d, unsigned int virq)
>> +{
>> +    if ( virq >= vgic_num_irqs(d) )
>> +        return false;
>> +
>> +    return !test_and_set_bit(virq, d->arch.vgic.allocated_irqs);
>> +}
>> +
>> +int vgic_allocate_virq(struct domain *d, bool spi)
>> +{
>> +    int first, end;
>> +    unsigned int virq;
>> +
>> +    if ( !spi )
>> +    {
>> +        /* We only allocate PPIs. SGIs are all reserved */
>> +        first = 16;
>> +        end = 32;
>> +    }
>> +    else
>> +    {
>> +        first = 32;
>> +        end = vgic_num_irqs(d);
>> +    }
>> +
>> +    /*
>> +     * There is no spinlock to protect allocated_irqs, therefore
>> +     * test_and_set_bit may fail. If so retry it.
>> +     */
>> +    do
>> +    {
>> +        virq = find_next_zero_bit(d->arch.vgic.allocated_irqs, end, first);
>> +        if ( virq >= end )
>> +            return -1;
>> +    } while ( test_and_set_bit(virq, d->arch.vgic.allocated_irqs) );
>> +
>> +    return virq;
>> +}
>> +
>> +void vgic_free_virq(struct domain *d, unsigned int virq)
>> +{
>> +    clear_bit(virq, d->arch.vgic.allocated_irqs);
>> +}
>> +
>>  struct irq_desc *vgic_get_hw_irq_desc(struct domain *d, struct vcpu *v,
>>                                        unsigned int virq)
>>  {
>> -- 
>> 2.14.1
>>

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