Re: [Xen-devel] [RFC PATCH 08/24] ARM: GICv3: introduce separate pending_irq structs for LPIs

[Julien Grall <julien.grall@xxxxxxx>]

Hi Andre,

On 28/09/16 19:24, Andre Przywara wrote:
> +/*
> + * Holding struct pending_irq's for each possible virtual LPI in each domain
> + * requires too much Xen memory, also a malicious guest could potentially
> + * spam Xen with LPI map requests. We cannot cover those with (guest allocated)
> + * ITS memory, so we use a dynamic scheme of allocating struct pending_irq's
> + * on demand.
> + */
> +struct pending_irq *lpi_to_pending(struct vcpu *v, unsigned int lpi,
> +                                   bool allocate)
> +{
> +    struct lpi_pending_irq *lpi_irq, *empty = NULL;
> +
> +    /* TODO: locking! */
> +    list_for_each_entry(lpi_irq, &v->arch.vgic.pending_lpi_list, entry)
> +    {
> +        if ( lpi_irq->pirq.irq == lpi )
> +            return &lpi_irq->pirq;
> +
> +        if ( lpi_irq->pirq.irq == 0 && !empty )
> +            empty = lpi_irq;
> +    }
> +
> +    if ( !allocate )
> +        return NULL;
> +
> +    if ( !empty )
> +    {
> +        empty = xzalloc(struct lpi_pending_irq);
xzalloc can return NULL if we fail to allocate memory.

> +        vgic_init_pending_irq(&empty->pirq, lpi);
> +        list_add_tail(&empty->entry, &v->arch.vgic.pending_lpi_list);
> +    } else
> +    {
> +        empty->pirq.status = 0;
> +        empty->pirq.irq = lpi;
> +    }
> +
> +    return &empty->pirq;
> +}
> +
Regards,

--
Julien Grall

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