On Mon, Oct 26, 2009 at 12:22:03PM -0400, Gregory Haskins wrote:
> Certain GSI's support lockless injecton, but we have no way to detect
> which ones at the GSI level. Knowledge of this attribute will be
> useful later in the series so that we can optimize irqfd injection
> paths for cases where we know the code will not sleep. Therefore,
> we provide an API to query a specific GSI.
>
> Signed-off-by: Gregory Haskins <ghaskins@xxxxxxxxxx>
> ---
>
> include/linux/kvm_host.h | 2 ++
> virt/kvm/irq_comm.c | 35 ++++++++++++++++++++++++++++++++++-
> 2 files changed, 36 insertions(+), 1 deletions(-)
>
> diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h
> index 1fe135d..01151a6 100644
> --- a/include/linux/kvm_host.h
> +++ b/include/linux/kvm_host.h
> @@ -119,6 +119,7 @@ struct kvm_memory_slot {
> struct kvm_kernel_irq_routing_entry {
> u32 gsi;
> u32 type;
> + bool lockless;
So lockless is the same as type == MSI from below?
If the idea is to make it extensible for the future,
let's just add an inline function, we don't need a field for this.
> int (*set)(struct kvm_kernel_irq_routing_entry *e,
> struct kvm *kvm, int irq_source_id, int level);
> union {
> @@ -420,6 +421,7 @@ void kvm_get_intr_delivery_bitmask(struct kvm_ioapic *ioapic,
> unsigned long *deliver_bitmask);
> #endif
> int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level);
> +int kvm_irq_check_lockless(struct kvm *kvm, u32 irq);
> void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin);
> void kvm_register_irq_ack_notifier(struct kvm *kvm,
> struct kvm_irq_ack_notifier *kian);
> diff --git a/virt/kvm/irq_comm.c b/virt/kvm/irq_comm.c
> index db2553f..a7fd487 100644
> --- a/virt/kvm/irq_comm.c
> +++ b/virt/kvm/irq_comm.c
> @@ -173,6 +173,35 @@ int kvm_set_irq(struct kvm *kvm, int irq_source_id, u32 irq, int level)
> return ret;
> }
>
> +int kvm_irq_check_lockless(struct kvm *kvm, u32 irq)
> +{
> + struct kvm_kernel_irq_routing_entry *e;
> + struct kvm_irq_routing_table *irq_rt;
> + struct hlist_node *n;
> + int ret = -ENOENT;
> + int idx;
> +
> + idx = srcu_read_lock(&kvm->irq_routing.srcu);
> + irq_rt = rcu_dereference(kvm->irq_routing.table);
> + if (irq < irq_rt->nr_rt_entries)
> + hlist_for_each_entry(e, n, &irq_rt->map[irq], link) {
> + if (!e->lockless) {
> + /*
> + * all destinations need to be lockless to
> + * declare that the GSI as a whole is also
> + * lockless
> + */
> + ret = 0;
> + break;
> + }
> +
> + ret = 1;
> + }
> + srcu_read_unlock(&kvm->irq_routing.srcu, idx);
> +
> + return ret;
> +}
> +
> void kvm_notify_acked_irq(struct kvm *kvm, unsigned irqchip, unsigned pin)
> {
> struct kvm_irq_ack_notifier *kian;
> @@ -310,18 +339,22 @@ static int setup_routing_entry(struct kvm_irq_routing_table *rt,
> int delta;
> struct kvm_kernel_irq_routing_entry *ei;
> struct hlist_node *n;
> + bool lockless = ue->type == KVM_IRQ_ROUTING_MSI;
>
> /*
> * Do not allow GSI to be mapped to the same irqchip more than once.
> * Allow only one to one mapping between GSI and MSI.
> + * Do not allow mixed lockless vs locked variants to coexist.
Userspace has no idea which entries are lockless and which are not:
this is an implementation detail - so it might not be able to avoid
illegal combinations.
Since this is called on an ioctl, can the rule be formulated in a way
that makes sense for userspace?
> */
> hlist_for_each_entry(ei, n, &rt->map[ue->gsi], link)
> if (ei->type == KVM_IRQ_ROUTING_MSI ||
> - ue->u.irqchip.irqchip == ei->irqchip.irqchip)
> + ue->u.irqchip.irqchip == ei->irqchip.irqchip ||
> + ei->lockless != lockless)
So this check seems like it does nothing, because lockless is same as
MSI, and MSI is always 1:1? Intentional?
> return r;
>
> e->gsi = ue->gsi;
> e->type = ue->type;
> + e->lockless = lockless;
> switch (ue->type) {
> case KVM_IRQ_ROUTING_IRQCHIP:
> delta = 0;
>
> --
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