On Tue, 09 Jul 2013 15:27:14 +0200 Christian Borntraeger <borntraeger@xxxxxxxxxx> wrote: > On 09/07/13 13:34, Cornelia Huck wrote: > > Handle the new CCW_CMD_SET_IND_ADAPTER command enabling adapter interrupts > > on guest request. When active, host->guest notifications will be handled > > via global_indicator -> queue indicators instead of queue indicators + > > subchannel I/O interrupt. Indicators for virtqueues may be present at an > > offset. > > > > You might want to add why we want adapter interrupts: > - no test subchannel -> less qemu mutex contention > - no test subchannel -> we can implement something like irqfd without moving > most of ccw device mgmt into the kernel > - interrupt coalescing > - the guest common I/O layer already supports adapter interrupts > for all newer hardware How about the following: With traditional I/O interrupts, status needs to be collected from the subchannel via TEST SUBCHANNEL as well. With adapter interrupts, we - avoid the extra exit due to TEST SUBCHANNEL - can deliver multiple queue interrupts via the same I/O interrupt - make it possible to implement irqfds without having to track subchannel status inside kvm > > > the interesting part of this patch is the guest<->host interface. As far as I > can see, we are able to register > - an isc per device > - an arbitrary summary indicator byte per device > - an arbitrary bit position in guest memory where the queue indicator bits of this > device start > > This allows for packing the indicators for all virtqueues of all devices or > spreading them in memory. The layout and amount of coalescing of bits is then > an optimization that can be changed all the time without the need to change > the interface. > > > Signed-off-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx> > Acked-by: Christian Borntraeger <borntraeger@xxxxxxxxxx> Thx! -- 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
