On Fri, Jan 30 2026, Eric Farman <[email protected]> wrote: > On Mon, 2026-01-26 at 23:00 +0100, Halil Pasic wrote: >> On Mon, 26 Jan 2026 19:40:09 +0300 >> Vladimir Sementsov-Ogievskiy <[email protected]> wrote: >> >> > > > +/** >> > > > + * virtio_queue_set_guest_notifier - set/unset queue or config guest >> > > > + * notifier >> > > > + * >> > > > + * @vdev: the VirtIO device >> > > > + * @n: queue number, or VIRTIO_CONFIG_IRQ_IDX to set config notifer >> > > >> > > Semantically are mixing queue numbers and interrupt indexes here. >> > >> > That's preexisting logic in virtio_pci_set_guest_notifier_fd_handler(). >> > >> > But, you are right, that's doesn't answer the question, is it good to share >> > the logic with mmio and ccw. >> > >> > Is config notifier only pci specific, or similar feature may appear in >> > future >> > for mmio and/or ccw? >> >> AFAIR there is no notifier for ccw. A possible explanation for >> that is, that AFAIK that config space notifications (device -> driver) >> are always classic I/O interrupts while queue indicators can be so called >> adapter I/O interrupts and irqfd is only available for adapter I/O >> interrupts. >> >> If you like you can have a look at >> "4.3.2.6 Setting Up Indicators" in >> https://docs.oasis-open.org/virtio/virtio/v1.3/csd01/virtio-v1.3-csd01.html#x1-1940003 >> >> I see no reason why virtio_config_guest_notifier_read() based, i.e >> !irqfd virtio config notifier should not exist or would not work. And I >> guess it is needed for certain vhost things. But nevertheless, I can't >> find the place where a virtio-ccw config notifier is set up. >> >> Eric, what is your opinion on this? My current thinking is that >> virtio-ccw not having a config notifier is basically a bug. > > (Sorry that I missed this; thanks for the ping, Halil) > > Yeah, we don't have have such a config notifier and I don't recall the > history behind it.
Adapter interrupts were not a thing for virtio-ccw in the beginning (we only added the airq infrastructure later IIRC, so all interrupts were "classic" subchannel-based interrupts.) > But I don't know that it's a bug; spec points out config notifications for > ccw come as unsolicited > interrupts versus config notifier, so not having one is fine by me as far as > this refactoring goes. > I'll add it to a list of things to play around with, though. I think I agree. (Although my brain is already more than halfway into the weekend...)
