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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

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 :-)

Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>


> ---
>  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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