On Thu, Oct 24, 2019 at 11:30:31AM +0800, Yongji Xie wrote: > 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.
Good points, thanks! I will send v2 that works for all vhost-user devices (including blk, scsi, and net). Stefan
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