On 11/18/2010 04:22 AM, Sheng Yang wrote:
On Wednesday 17 November 2010 22:01:41 Avi Kivity wrote: > On 11/15/2010 11:15 AM, Sheng Yang wrote: > > We need to query the entry later. > > > > +int kvm_get_irq_routing_entry(struct kvm *kvm, int gsi, > > + struct kvm_kernel_irq_routing_entry *entry) > > +{ > > + int count = 0; > > + struct kvm_kernel_irq_routing_entry *ei = NULL; > > + struct kvm_irq_routing_table *irq_rt; > > + struct hlist_node *n; > > + > > + rcu_read_lock(); > > + irq_rt = rcu_dereference(kvm->irq_routing); > > + if (gsi< irq_rt->nr_rt_entries) > > + hlist_for_each_entry(ei, n,&irq_rt->map[gsi], link) > > + count++; > > + if (count == 1) > > + *entry = *ei; > > + rcu_read_unlock(); > > + > > + return (count != 1); > > +} > > + > > Not good form to rely on ei being valid after the loop. > > I guess this is only useful for msi? Need to document it.May can be used for others later, it's somehow generic. Where should I document it?
Non-msi interrupts (wires) can be wired to more than one interrupt line (and often are - pic/ioapic).
You can document it by adding _msi to the name.
> > *entry may be stale after rcu_read_unlock(). Is this a problem? I suppose not. All MSI-X MMIO accessing would be executed without delay, so no re- order issue would happen. If the guest is reading and writing the field at the same time(from two cpus), it should got some kinds of sync method for itself - or it may not care what's the reading result(like the one after msix_mask_irq()).
I guess so. Michael/Alex? -- error compiling committee.c: too many arguments to function -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
