On Mon, 21 Oct 2019 at 19:40, Stefan Hajnoczi <stefa...@redhat.com> wrote: > > Host notifiers are used in several cases: > 1. Traditional ioeventfd where virtqueue notifications are handled in > the main loop thread. > 2. IOThreads (aio_handle_output) where virtqueue notifications are > handled in an IOThread AioContext. > 3. vhost where virtqueue notifications are handled by kernel vhost or > a vhost-user device backend. > > Most virtqueue notifications from the guest use the ioeventfd mechanism, > but there are corner cases where QEMU code calls virtio_queue_notify(). > This currently honors the host notifier for the IOThreads > aio_handle_output case, but not for the vhost case. The result is that > vhost does not receive virtqueue notifications from QEMU when > virtio_queue_notify() is called. > > This patch extends virtio_queue_notify() to set the host notifier > whenever it is enabled instead of calling the vq->(aio_)handle_output() > function directly. > > This fixes the vhost case although it does add a trip through the > eventfd for the traditional ioeventfd case. I don't think it's worth > adding a fast path for the traditional ioeventfd case because calling > virtio_queue_notify() is rare when ioeventfd is enabled. > > Reported-by: Felipe Franciosi <fel...@nutanix.com> > Signed-off-by: Stefan Hajnoczi <stefa...@redhat.com> > --- > Felipe and Yongji: Only tested with "make check". Please try > vhost-user-scsi/blk and let us know if it fixes the issue. >
I can see the vhost-user-blk issue is fixed by this patch after the below patch applied: diff --git a/hw/virtio/vhost-user-blk-pci.c b/hw/virtio/vhost-user-blk-pci.c index 1dc834a..a32a439 100644 --- a/hw/virtio/vhost-user-blk-pci.c +++ b/hw/virtio/vhost-user-blk-pci.c @@ -46,6 +46,8 @@ static Property vhost_user_blk_pci_properties[] = { DEFINE_PROP_UINT32("class", VirtIOPCIProxy, class_code, 0), DEFINE_PROP_UINT32("vectors", VirtIOPCIProxy, nvectors, DEV_NVECTORS_UNSPECIFIED), + DEFINE_PROP_BIT("ioeventfd", VirtIOPCIProxy, flags, + VIRTIO_PCI_FLAG_USE_IOEVENTFD_BIT, true), DEFINE_PROP_END_OF_LIST(), }; > include/hw/virtio/virtio-bus.h | 7 +++++++ > hw/virtio/virtio.c | 4 +++- > 2 files changed, 10 insertions(+), 1 deletion(-) > > diff --git a/include/hw/virtio/virtio-bus.h b/include/hw/virtio/virtio-bus.h > index 38c9399cd4..28ca51cb4c 100644 > --- a/include/hw/virtio/virtio-bus.h > +++ b/include/hw/virtio/virtio-bus.h > @@ -139,6 +139,13 @@ static inline VirtIODevice > *virtio_bus_get_device(VirtioBusState *bus) > > /* Return whether the proxy allows ioeventfd. */ > bool virtio_bus_ioeventfd_enabled(VirtioBusState *bus); > + > +/* Return whether ioeventfd has been started. */ > +static inline bool virtio_bus_ioeventfd_started(VirtioBusState *bus) > +{ > + return bus->ioeventfd_started; > +} > + > /* Start the ioeventfd. */ > int virtio_bus_start_ioeventfd(VirtioBusState *bus); > /* Stop the ioeventfd. */ > diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c > index 527df03bfd..abdcec00cd 100644 > --- a/hw/virtio/virtio.c > +++ b/hw/virtio/virtio.c > @@ -1567,6 +1567,8 @@ static void virtio_queue_notify_vq(VirtQueue *vq) > > void virtio_queue_notify(VirtIODevice *vdev, int n) > { > + BusState *qbus = qdev_get_parent_bus(DEVICE(vdev)); > + VirtioBusState *vbus = VIRTIO_BUS(qbus); > VirtQueue *vq = &vdev->vq[n]; > > if (unlikely(!vq->vring.desc || vdev->broken)) { > @@ -1574,7 +1576,7 @@ void virtio_queue_notify(VirtIODevice *vdev, int n) > } > > trace_virtio_queue_notify(vdev, vq - vdev->vq, vq); > - if (vq->handle_aio_output) { > + if (virtio_bus_ioeventfd_started(vbus)) { Need to check whether vq->host_notifier is valid or not here. Otherwise, it could break the ctrl_vq in vhost_net device. Thanks, Yongji