On Tue, Nov 05, 2019 at 03:09:46PM +0100, Stefan Hajnoczi 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. We track the host notifier state for each virtqueue > separately since some devices may use it only for certain virtqueues. > > 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> > --- > v2: > * Track host notifier enabled/disabled state per virtqueue [Yongji Xie] > * Tested with contrib/vhost-user-blk and contrib/vhost-user-scsi
Hi Michael,
Please consider this for QEMU 4.2 so that SeaBIOS works even when it
selects the VP_ACCESS_PCICFG access mode.
Felipe tested this successfully yesterday.
Stefan
> hw/virtio/virtio-bus.c | 4 ++++
> hw/virtio/virtio.c | 9 ++++++++-
> include/hw/virtio/virtio.h | 1 +
> 3 files changed, 13 insertions(+), 1 deletion(-)
>
> diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
> index b2c804292e..d6332d45c3 100644
> --- a/hw/virtio/virtio-bus.c
> +++ b/hw/virtio/virtio-bus.c
> @@ -288,6 +288,10 @@ int virtio_bus_set_host_notifier(VirtioBusState *bus,
> int n, bool assign)
> k->ioeventfd_assign(proxy, notifier, n, false);
> }
>
> + if (r == 0) {
> + virtio_queue_set_host_notifier_enabled(vq, assign);
> + }
> +
> return r;
> }
>
> diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
> index 762df12f4c..04716b5f6c 100644
> --- a/hw/virtio/virtio.c
> +++ b/hw/virtio/virtio.c
> @@ -128,6 +128,7 @@ struct VirtQueue
> VirtIODevice *vdev;
> EventNotifier guest_notifier;
> EventNotifier host_notifier;
> + bool host_notifier_enabled;
> QLIST_ENTRY(VirtQueue) node;
> };
>
> @@ -2271,7 +2272,7 @@ void virtio_queue_notify(VirtIODevice *vdev, int n)
> }
>
> trace_virtio_queue_notify(vdev, vq - vdev->vq, vq);
> - if (vq->handle_aio_output) {
> + if (vq->host_notifier_enabled) {
> event_notifier_set(&vq->host_notifier);
> } else if (vq->handle_output) {
> vq->handle_output(vdev, vq);
> @@ -3145,6 +3146,7 @@ void virtio_init(VirtIODevice *vdev, const char *name,
> vdev->vq[i].vector = VIRTIO_NO_VECTOR;
> vdev->vq[i].vdev = vdev;
> vdev->vq[i].queue_index = i;
> + vdev->vq[i].host_notifier_enabled = false;
> }
>
> vdev->name = name;
> @@ -3436,6 +3438,11 @@ EventNotifier
> *virtio_queue_get_host_notifier(VirtQueue *vq)
> return &vq->host_notifier;
> }
>
> +void virtio_queue_set_host_notifier_enabled(VirtQueue *vq, bool enabled)
> +{
> + vq->host_notifier_enabled = enabled;
> +}
> +
> int virtio_queue_set_host_notifier_mr(VirtIODevice *vdev, int n,
> MemoryRegion *mr, bool assign)
> {
> diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
> index 3448d67d2a..c32a815303 100644
> --- a/include/hw/virtio/virtio.h
> +++ b/include/hw/virtio/virtio.h
> @@ -312,6 +312,7 @@ int virtio_device_grab_ioeventfd(VirtIODevice *vdev);
> void virtio_device_release_ioeventfd(VirtIODevice *vdev);
> bool virtio_device_ioeventfd_enabled(VirtIODevice *vdev);
> EventNotifier *virtio_queue_get_host_notifier(VirtQueue *vq);
> +void virtio_queue_set_host_notifier_enabled(VirtQueue *vq, bool enabled);
> void virtio_queue_host_notifier_read(EventNotifier *n);
> void virtio_queue_aio_set_host_notifier_handler(VirtQueue *vq, AioContext
> *ctx,
> VirtIOHandleAIOOutput
> handle_output);
> --
> 2.23.0
>
>
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