On Tue, 2 Aug 2016 10:39:22 +0800
Jason Wang <address@hidden> wrote:
On 2016年08月02日 02:00, Cornelia Huck wrote:
On Mon, 1 Aug 2016 16:07:58 +0800
Jason Wang <address@hidden> wrote:
+ if (k->query_guest_notifiers &&
+ k->query_guest_notifiers(qbus->parent) &&
+ virtio_queue_vector(vdev, idx) == VIRTIO_NO_VECTOR) {
I'm trying to imagine what this means for virtio-ccw. Keep in mind that
we don't have the concept of setting a 'vector' by the OS (the vector
is setup internally to the queue index and the OS does not see it.)
->query_guest_notifiers() is true if the OS has enabled the subchannel
of the proxy device (i.e., if it is enabled for doing *anything* with
the subchannel, regardless whether the OS wants to be notified or is
planning to poll.) The second condition will never hold true for any
valid queue once the OS has setup the queues.
I see, so If I understand correctly, there's no way to detect whether or
not guest will use a specific virtqueue interrupt?
Yes. The guest will either be notified for any virtqueue (if it
registered indicators; this is always done for every vq of the device
at once), or for none.
So this won't break anything for virtio-ccw AFAICS, but I don't think
we gain anything.
Yes, but if we could infer whether or not polling is used in the driver,
this is probably all we can do for ccw.
What we could do is check whether the driver has registed indicators
and disable setting up notification for any vq of the device if not.
But I'm not sure an always-polling driver is worth optimizing for.