Hi Marc,
On 11/06/2019 18:03, Marc Zyngier wrote:
> Add the basic data structure that expresses an MSI to LPI
> translation as well as the allocation/release hooks.
>
> THe size of the cache is arbitrarily defined as 4*nr_vcpus.
>
The size has been arbitrarily changed to 16*nr_vcpus :) .
Nit: The*
> Signed-off-by: Marc Zyngier <marc.zyngier@xxxxxxx>
> ---
> include/kvm/arm_vgic.h | 3 +++
> virt/kvm/arm/vgic/vgic-init.c | 5 ++++
> virt/kvm/arm/vgic/vgic-its.c | 49 +++++++++++++++++++++++++++++++++++
> virt/kvm/arm/vgic/vgic.h | 2 ++
> 4 files changed, 59 insertions(+)
>
> diff --git a/include/kvm/arm_vgic.h b/include/kvm/arm_vgic.h
> index c36c86f1ec9a..ca7bcf52dc85 100644
> --- a/include/kvm/arm_vgic.h
> +++ b/include/kvm/arm_vgic.h
> @@ -260,6 +260,9 @@ struct vgic_dist {
> struct list_head lpi_list_head;
> int lpi_list_count;
>
> + /* LPI translation cache */
> + struct list_head lpi_translation_cache;
> +
> /* used by vgic-debug */
> struct vgic_state_iter *iter;
>
> diff --git a/virt/kvm/arm/vgic/vgic-init.c b/virt/kvm/arm/vgic/vgic-init.c
> index 3bdb31eaed64..c7c4c77dd430 100644
> --- a/virt/kvm/arm/vgic/vgic-init.c
> +++ b/virt/kvm/arm/vgic/vgic-init.c
> @@ -64,6 +64,7 @@ void kvm_vgic_early_init(struct kvm *kvm)
> struct vgic_dist *dist = &kvm->arch.vgic;
>
> INIT_LIST_HEAD(&dist->lpi_list_head);
> + INIT_LIST_HEAD(&dist->lpi_translation_cache);
> raw_spin_lock_init(&dist->lpi_list_lock);
> }
>
> @@ -305,6 +306,7 @@ int vgic_init(struct kvm *kvm)
> }
>
> if (vgic_has_its(kvm)) {
> + vgic_lpi_translation_cache_init(kvm);
> ret = vgic_v4_init(kvm);
> if (ret)
> goto out;
> @@ -346,6 +348,9 @@ static void kvm_vgic_dist_destroy(struct kvm *kvm)
> INIT_LIST_HEAD(&dist->rd_regions);
> }
>
> + if (vgic_has_its(kvm))
> + vgic_lpi_translation_cache_destroy(kvm);
> +
> if (vgic_supports_direct_msis(kvm))
> vgic_v4_teardown(kvm);
> }
> diff --git a/virt/kvm/arm/vgic/vgic-its.c b/virt/kvm/arm/vgic/vgic-its.c
> index 44ceaccb18cf..ce9bcddeb7f1 100644
> --- a/virt/kvm/arm/vgic/vgic-its.c
> +++ b/virt/kvm/arm/vgic/vgic-its.c
> @@ -149,6 +149,14 @@ struct its_ite {
> u32 event_id;
> };
>
> +struct vgic_translation_cache_entry {
> + struct list_head entry;
> + phys_addr_t db;
> + u32 devid;
> + u32 eventid;
> + struct vgic_irq *irq;
> +};
> +
> /**
> * struct vgic_its_abi - ITS abi ops and settings
> * @cte_esz: collection table entry size
> @@ -1668,6 +1676,45 @@ static int vgic_register_its_iodev(struct kvm *kvm, struct vgic_its *its,
> return ret;
> }
>
> +/* Default is 16 cached LPIs per vcpu */
> +#define LPI_DEFAULT_PCPU_CACHE_SIZE 16
> +
> +void vgic_lpi_translation_cache_init(struct kvm *kvm)
> +{
> + struct vgic_dist *dist = &kvm->arch.vgic;
> + unsigned int sz;
> + int i;
> +
> + if (!list_empty(&dist->lpi_translation_cache))
> + return;
> +
> + sz = atomic_read(&kvm->online_vcpus) * LPI_DEFAULT_PCPU_CACHE_SIZE;
> +
> + for (i = 0; i < sz; i++) {
> + struct vgic_translation_cache_entry *cte;
> +
> + /* An allocation failure is not fatal */
> + cte = kzalloc(sizeof(*cte), GFP_KERNEL);
> + if (WARN_ON(!cte))
> + break;
> +
> + INIT_LIST_HEAD(&cte->entry);
> + list_add(&cte->entry, &dist->lpi_translation_cache);
Going through the series, it looks like this list is either empty
(before the cache init) or has a fixed number
(LPI_DEFAULT_PCPU_CACHE_SIZE * nr_cpus) of entries. And the list never
grows nor shrinks throughout the series, so it seems odd to be using a
list here.
Is there a reason for not using a dynamically allocated array instead of
the list? (does list_move() provide a big perf advantage over swapping
the data from one array entry to another? Or is there some other
facility I am missing?
Cheers,
--
Julien Thierry
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