On Mon, Oct 17, 2011 at 09:28:12PM +0200, Jan Kiszka wrote: > On 2011-10-17 17:48, Michael S. Tsirkin wrote: > > On Mon, Oct 17, 2011 at 11:28:02AM +0200, Jan Kiszka wrote: > >> This optimization was only required to keep KVM route usage low. Now > >> that we solve that problem via lazy updates, we can drop the field. We > >> still need interfaces to clear pending vectors, though (and we have to > >> make use of them more broadly - but that's unrelated to this patch). > >> > >> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx> > > > > Lazy updates should be an implementation detail. > > IMO resource tracking of vectors makes sense > > as an API. Making devices deal with pending > > vectors as a concept, IMO, does not. > > There is really no use for tracking the vector lifecycle once we have > lazy updates (except for static routes). It's a way too invasive > concept, and it's not needed for anything but KVM. I think it's needed. The PCI spec states that when the device does not need an interrupt anymore, it should clear the pending bit. The use/unuse is IMO a decent API for this, because it uses a familiar resource tracking concept. Exposing this knowledge of msix to devices seems like a worse API. > > If you want an example, check > http://permalink.gmane.org/gmane.comp.emulators.kvm.devel/70915 and > compare it to the changes done to hpet in this series. > > Jan > This seems to be a general argument that lazy updates are good? I have no real problem with them, besides the fact that we need an API to reserve space in the routing table so that device setup can fail upfront. -- MST -- To unsubscribe from this list: send the line "unsubscribe kvm" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
