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Message-ID: <20091028074623.GB22784@redhat.com> Date: Wed, 28 Oct 2009 09:46:23 +0200 From: "Michael S. Tsirkin" <mst@...hat.com> To: Gregory Haskins <ghaskins@...ell.com> Cc: kvm@...r.kernel.org, alacrityvm-devel@...ts.sourceforge.net, linux-kernel@...r.kernel.org Subject: Re: [KVM PATCH v3 2/3] KVM: export lockless GSI attribute 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@...ell.com> > --- > > 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; > > -- > To unsubscribe from this list: send the line "unsubscribe kvm" in > the body of a message to majordomo@...r.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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