On Thu, May 05, 2016 at 11:13:37AM +0200, Ladi Prosek wrote: > There is a discrepancy between dataplane and no-dataplane virtio > behavior with respect to the ISR status register and MSI-X > capability. > > Without dataplane the Queue interrupt ISR status bit is set > regardless of how the notification is delivered to the guest. > > With dataplane the Queue interrupt ISR status bit is set only > if the notification is delivered as an IRQ. > > While both conform to the spec, QEMU should be consistent to > minimize surprises with broken drivers. > > This RFC patch shows the relevant code location and contains a > possible fix which makes QEMU set the bit on the MSI dataplane > code path. > > Signed-off-by: Ladi Prosek <lpro...@redhat.com>
How is this supposed to work when injecting interrupts using irqfd? If anything, I would rather drop setting the flag on non-dataplane. > --- > hw/virtio/virtio.c | 19 ++++++++++++++----- > 1 file changed, 14 insertions(+), 5 deletions(-) > > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index 08275a9..4053313 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -1192,7 +1192,7 @@ void virtio_notify(VirtIODevice *vdev, VirtQueue *vq) > } > > trace_virtio_notify(vdev, vq); > - vdev->isr |= 0x01; > + vdev->isr |= 0x01; // <= here we set ISR status even if we don't raise > IRQ > virtio_notify_vector(vdev, vq->vector); > } > > @@ -1757,16 +1757,25 @@ static void > virtio_queue_guest_notifier_read(EventNotifier *n) > } > } > > +static void virtio_queue_guest_notifier_read_irqfd(EventNotifier *n) > +{ > + VirtQueue *vq = container_of(n, VirtQueue, guest_notifier); > + if (event_notifier_test_and_clear(n)) { > + vq->vdev->isr |= 0x01; > + } > +} > + > void virtio_queue_set_guest_notifier_fd_handler(VirtQueue *vq, bool assign, > bool with_irqfd) > { > - if (assign && !with_irqfd) { > + if (assign) { > event_notifier_set_handler(&vq->guest_notifier, > - virtio_queue_guest_notifier_read); > + with_irqfd ? > + virtio_queue_guest_notifier_read_irqfd : > + virtio_queue_guest_notifier_read); > } else { > event_notifier_set_handler(&vq->guest_notifier, NULL); > - } > - if (!assign) { > + > /* Test and clear notifier before closing it, > * in case poll callback didn't have time to run. */ > virtio_queue_guest_notifier_read(&vq->guest_notifier); > -- > 2.5.5