On Tue, Jun 23, 2009 at 07:41:12AM -0400, Gregory Haskins wrote: > Avi Kivity wrote: > > On 06/22/2009 07:08 PM, Michael S. Tsirkin wrote: > >> On Mon, Jun 22, 2009 at 11:45:00AM -0400, Gregory Haskins wrote: > >> > >>> Michael S. Tsirkin wrote: > >>> > >>>> It seems that a lot of complexity and trickiness with iosignalfd is > >>>> handling the group/item relationship, which comes about because kvm > >>>> does > >>>> not currently let a device on the bus claim a write transaction > >>>> based on the > >>>> value written. This could be greatly simplified if the value written > >>>> was passed to the in_range check for write operation. We could then > >>>> simply make each kvm_iosignalfd a device on the bus. > >>>> > >>>> What does everyone think of the following lightly tested patch? > >>>> > >>>> > >>> Hi Michael, > >>> Its interesting, but I am not convinced its necessary. We > >>> created the > >>> group/item layout because iosignalfds are unique in that they are > >>> probably the only IO device that wants to do some kind of address > >>> aliasing. > >>> > >> > >> We actually already have aliasing: is_write flag is used for this > >> purpose. Actually, it's possible to remove is_write by passing > >> a null pointer in write_val for reads. I like this a bit less as > >> the code generated is less compact ... Avi, what do you think? > >> > > > > Greg, won't Michael's patch eliminate a big chunk from your iosignalfd > > patches? Seems like a win to me. > > Well, it really just moves that hunk from eventfd.c to kvm_main.c, where > I don't think anyone else will use it by iosignalfd. But if that is > what everyone wants, I guess I have no choice. Wait a bit before you start rebasing though please. I just had a brainwave and is rewriting this patch. > > > >> One is enough :) > >> Seriously, do you see that this saves you all of RCU, linked lists and > >> counters? You don't need to keep track of iofds, you don't need to > >> implement your own lookup logic - you just use the kvm device > >> and that's it. > >> > >> > > > > Yup. > > > > -- 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
