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    SubjectRe: [KVM PATCH v2 1/2] KVM: export lockless GSI attribute
    On 10/23/2009 04:38 AM, 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.
    >
    >

    Instead of a lockless attribute, how about a ->set_atomic() method. For
    msi this can be the same as ->set(), for non-msi it can be a function
    that schedules the work (which will eventually call ->set()).

    The benefit is that we make a decision only once, when preparing the
    routing entry, and install that decision in the routing entry instead of
    making it again and again later.

    > +int kvm_irq_check_lockless(struct kvm *kvm, u32 irq)
    >

    bool kvm_irq_check_lockless(...)

    > +{
    > + struct kvm_kernel_irq_routing_entry *e;
    > + struct kvm_irq_routing_table *irq_rt;
    > + struct hlist_node *n;
    > + int ret = -ENOENT;
    > +
    > + rcu_read_lock();
    > + irq_rt = rcu_dereference(kvm->irq_routing);
    > + if (irq< irq_rt->nr_rt_entries)
    > + hlist_for_each_entry(e, n,&irq_rt->map[irq], link)
    > + ret = e->lockless ? 1 : 0;
    >

    ret = e->lockless;

    > + rcu_read_unlock();
    > +
    > + return ret;
    > +}
    > +
    >

    --
    error compiling committee.c: too many arguments to function



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