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authorStefan Hajnoczi <stefanha@redhat.com>2019-11-05 15:09:46 +0100
committerMichael S. Tsirkin <mst@redhat.com>2019-11-06 06:35:00 -0500
commitfcccb271e0894bc04078ababb29d3d5e06b79892 (patch)
tree3e1b5e8ea018b85f6542cda0f8839f55b70bae98 /hw/virtio
parent977aff1045b01579e73020a271336e559cdd6b58 (diff)
virtio: notify virtqueue via host notifier when available
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 <felipe@nutanix.com> Signed-off-by: Stefan Hajnoczi <stefanha@redhat.com> Message-Id: <20191105140946.165584-1-stefanha@redhat.com> Reviewed-by: Michael S. Tsirkin <mst@redhat.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
Diffstat (limited to 'hw/virtio')
-rw-r--r--hw/virtio/virtio-bus.c4
-rw-r--r--hw/virtio/virtio.c9
2 files changed, 12 insertions, 1 deletions
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)
{