----- Original Message -----
> From: "Michael S. Tsirkin" <m...@redhat.com>
> To: "Paolo Bonzini" <pbonz...@redhat.com>
> Cc: qemu-devel@nongnu.org, "alex williamson" <alex.william...@redhat.com>,
> borntrae...@de.ibm.com, fel...@nutanix.com
> Sent: Wednesday, November 16, 2016 9:39:24 PM
> Subject: Re: [PATCH 3/3] virtio: set ISR on dataplane notifications
>
> On Wed, Nov 16, 2016 at 03:38:11PM -0500, Paolo Bonzini wrote:
> > > > +void virtio_notify_irqfd(VirtIODevice *vdev, VirtQueue *vq)
> > > > +{
> > > > + if (!virtio_should_notify(vdev, vq)) {
> > > > + return;
> > > > + }
> > > > +
> > > > + trace_virtio_notify_irqfd(vdev, vq);
> > > > + virtio_set_isr(vq->vdev, 0x1);
> > >
> > > So here, I think we need a comment with parts of
> > > the commit log.
> > >
> > > /*
> > > * virtio spec 1.0 says ISR bit 0 should be ignored with MSI, but
> > > * windows drivers included in virtio-win 1.8.0 (circa 2015)
> > > * for Windows 8.1 only are incorrectly polling this bit during shutdown
> > ^^^^^^^^^^^^^^^^
> >
> > Not sure it's only for Windows 8.1, in fact probably not.
>
> 8.1 on shutdown and others on crashdump or hibernation?
Even 8.1 is really a hibernation hidden behind a "Shut down" menu item.
Paolo
> > Looks good if you replace this line with
> >
> > "are incorrectly polling this bit during crashdump or hibernation"
> >
> > Paolo
> >
> > > * in MSI mode, causing a hang if this bit is never updated.
> > > * Next driver release from 2016 fixed this problem, so working around it
> > > * is not a must, but it's easy to do so let's do it here.
> > > *
> > > * Note: it's safe to update ISR from any thread as it was switched
> > > * to an atomic operation.
> > > */
> >
> >
> > >
> > >
> > >
> > > > + event_notifier_set(&vq->guest_notifier);
> > > > +}
> > > > +
> > > > void virtio_notify(VirtIODevice *vdev, VirtQueue *vq)
> > > > {
> > > > if (!virtio_should_notify(vdev, vq)) {
> > > > @@ -1990,7 +1994,7 @@ static void
> > > > virtio_queue_guest_notifier_read(EventNotifier *n)
> > > > {
> > > > VirtQueue *vq = container_of(n, VirtQueue, guest_notifier);
> > > > if (event_notifier_test_and_clear(n)) {
> > > > - virtio_irq(vq);
> > > > + virtio_notify_vector(vq->vdev, vq->vector);
> > > > }
> > > > }
> > > >
> > > > diff --git a/include/hw/virtio/virtio-scsi.h
> > > > b/include/hw/virtio/virtio-scsi.h
> > > > index 9fbc7d7..7375196 100644
> > > > --- a/include/hw/virtio/virtio-scsi.h
> > > > +++ b/include/hw/virtio/virtio-scsi.h
> > > > @@ -137,6 +137,5 @@ void virtio_scsi_push_event(VirtIOSCSI *s,
> > > > SCSIDevice
> > > > *dev,
> > > > void virtio_scsi_dataplane_setup(VirtIOSCSI *s, Error **errp);
> > > > int virtio_scsi_dataplane_start(VirtIODevice *s);
> > > > void virtio_scsi_dataplane_stop(VirtIODevice *s);
> > > > -void virtio_scsi_dataplane_notify(VirtIODevice *vdev, VirtIOSCSIReq
> > > > *req);
> > > >
> > > > #endif /* QEMU_VIRTIO_SCSI_H */
> > > > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> > > > index 835b085..ab0e030 100644
> > > > --- a/include/hw/virtio/virtio.h
> > > > +++ b/include/hw/virtio/virtio.h
> > > > @@ -181,6 +181,7 @@ void virtqueue_get_avail_bytes(VirtQueue *vq,
> > > > unsigned
> > > > int *in_bytes,
> > > > unsigned max_in_bytes, unsigned
> > > > max_out_bytes);
> > > >
> > > > bool virtio_should_notify(VirtIODevice *vdev, VirtQueue *vq);
> > > > +void virtio_notify_irqfd(VirtIODevice *vdev, VirtQueue *vq);
> > > > void virtio_notify(VirtIODevice *vdev, VirtQueue *vq);
> > > >
> > > > void virtio_save(VirtIODevice *vdev, QEMUFile *f);
> > > > @@ -280,7 +281,6 @@ void virtio_queue_host_notifier_read(EventNotifier
> > > > *n);
> > > > void virtio_queue_aio_set_host_notifier_handler(VirtQueue *vq,
> > > > AioContext
> > > > *ctx,
> > > > void
> > > > (*fn)(VirtIODevice *,
> > > > VirtQueue
> > > > *));
> > > > -void virtio_irq(VirtQueue *vq);
> > > > VirtQueue *virtio_vector_first_queue(VirtIODevice *vdev, uint16_t
> > > > vector);
> > > > VirtQueue *virtio_vector_next_queue(VirtQueue *vq);
> > > >
> > > > --
> > > > 2.9.3
> > >
>
