Hi Marc,
On 6/11/19 7:03 PM, Marc Zyngier wrote:
> On a successful translation, preserve the parameters in the LPI
> translation cache. Each translation is reusing the last slot
> in the list, naturally evincting the least recently used entry.
evicting
>
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> virt/kvm/arm/vgic/vgic-its.c | 86 ++++++++++++++++++++++++++++++++++++
> 1 file changed, 86 insertions(+)
>
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 0aa0cbbc3af6..62932458476a 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -546,6 +546,90 @@ static unsigned long vgic_mmio_read_its_idregs(struct kvm *kvm,
> return 0;
> }
>
> +static struct vgic_irq *__vgic_its_check_cache(struct vgic_dist *dist,
> + phys_addr_t db,
> + u32 devid, u32 eventid)
> +{
> + struct vgic_translation_cache_entry *cte;
> + struct vgic_irq *irq = NULL;
> +
> + list_for_each_entry(cte, &dist->lpi_translation_cache, entry) {
> + /*
> + * If we hit a NULL entry, there is nothing after this
> + * point.
> + */
> + if (!cte->irq)
> + break;
> +
> + if (cte->db == db &&
> + cte->devid == devid &&
> + cte->eventid == eventid) {
> + /*
> + * Move this entry to the head, as it is the
> + * most recently used.
> + */
> + list_move(&cte->entry, &dist->lpi_translation_cache);
> + irq = cte->irq;
> + break;
> + }
> + }
> +
> + return irq;
> +}
> +
> +static void vgic_its_cache_translation(struct kvm *kvm, struct vgic_its *its,
> + u32 devid, u32 eventid,
> + struct vgic_irq *irq)
> +{
> + struct vgic_dist *dist = &kvm->arch.vgic;
> + struct vgic_translation_cache_entry *cte;
> + unsigned long flags;
> + phys_addr_t db;
> +
> + /* Do not cache a directly injected interrupt */
> + if (irq->hw)
> + return;
> +
> + raw_spin_lock_irqsave(&dist->lpi_list_lock, flags);
> +
> + if (unlikely(list_empty(&dist->lpi_translation_cache)))
> + goto out;
> +
> + /*
> + * We could have raced with another CPU caching the same
> + * translation behind our back, so let's check it is not in
> + * already
> + */
> + db = its->vgic_its_base + GITS_TRANSLATER;
> + if (__vgic_its_check_cache(dist, db, devid, eventid))
> + goto out;
> +
> + /* Always reuse the last entry (LRU policy) */
> + cte = list_last_entry(&dist->lpi_translation_cache,
> + typeof(*cte), entry);
> +
> + /*
> + * Caching the translation implies having an extra reference
> + * to the interrupt, so drop the potential reference on what
> + * was in the cache, and increment it on the new interrupt.
> + */
> + if (cte->irq)
> + __vgic_put_lpi_locked(kvm, cte->irq);
> +
> + vgic_get_irq_kref(irq);
> +
> + cte->db = db;
> + cte->devid = devid;
> + cte->eventid = eventid;
> + cte->irq = irq;
> +
> + /* Move the new translation to the head of the list */
> + list_move(&cte->entry, &dist->lpi_translation_cache);
> +
> +out:
> + raw_spin_unlock_irqrestore(&dist->lpi_list_lock, flags);
> +}
> +
> void vgic_its_invalidate_cache(struct kvm *kvm)
> {
> struct vgic_dist *dist = &kvm->arch.vgic;
> @@ -589,6 +673,8 @@ int vgic_its_resolve_lpi(struct kvm *kvm, struct vgic_its *its,
> if (!vcpu->arch.vgic_cpu.lpis_enabled)
> return -EBUSY;
>
> + vgic_its_cache_translation(kvm, its, devid, eventid, ite->irq);
> +
> *irq = ite->irq;
> return 0;
> }
>
Reviewed-by: Eric Auger <eric.auger@xxxxxxxxxx>
Thanks
Eric
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