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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [qemu-xen master] virtio: introduce grab/release_ioeventfd to fix vhost
commit 310837de6c1e0badfd736b1b316b1698c53120a7
Author: Paolo Bonzini <pbonzini@xxxxxxxxxx>
AuthorDate: Fri Nov 18 16:07:00 2016 +0100
Commit: Michael S. Tsirkin <mst@xxxxxxxxxx>
CommitDate: Fri Nov 18 17:29:25 2016 +0200
virtio: introduce grab/release_ioeventfd to fix vhost
Following the recent refactoring of virtio notifiers [1], more specifically
the patch ed08a2a0b ("virtio: use virtio_bus_set_host_notifier to
start/stop ioeventfd") that uses virtio_bus_set_host_notifier [2]
by default, core virtio code requires 'ioeventfd_started' to be set
to true/false when the host notifiers are configured.
When vhost is stopped and started, however, there is a stop followed by
another start. Since ioeventfd_started was never set to true, the 'stop'
operation triggered by virtio_bus_set_host_notifier() will not result
in a call to virtio_pci_ioeventfd_assign(assign=false). This leaves
the memory regions with stale notifiers and results on the next start
triggering the following assertion:
kvm_mem_ioeventfd_add: error adding ioeventfd: File exists
Aborted
This patch reintroduces (hopefully in a cleaner way) the concept
that was present with ioeventfd_disabled before the refactoring.
When ioeventfd_grabbed>0, ioeventfd_started tracks whether ioeventfd
should be enabled or not, but ioeventfd is actually not started at
all until vhost releases the host notifiers.
[1] http://lists.nongnu.org/archive/html/qemu-devel/2016-10/msg07748.html
[2] http://lists.nongnu.org/archive/html/qemu-devel/2016-10/msg07760.html
Reported-by: Felipe Franciosi <felipe@xxxxxxxxxxx>
Reported-by: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Reported-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Fixes: ed08a2a0b ("virtio: use virtio_bus_set_host_notifier to start/stop
ioeventfd")
Reviewed-by: Cornelia Huck <cornelia.huck@xxxxxxxxxx>
Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
Tested-by: Alexey Kardashevskiy <aik@xxxxxxxxx>
Tested-by: Farhan Ali <alifm@xxxxxxxxxxxxxxxxxx>
Tested-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
Reviewed-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
Signed-off-by: Michael S. Tsirkin <mst@xxxxxxxxxx>
---
hw/virtio/vhost.c | 14 +++++-----
hw/virtio/virtio-bus.c | 58 ++++++++++++++++++++++++++++++++++--------
hw/virtio/virtio.c | 16 ++++++++++++
include/hw/virtio/virtio-bus.h | 14 ++++++++++
include/hw/virtio/virtio.h | 2 ++
5 files changed, 86 insertions(+), 18 deletions(-)
diff --git a/hw/virtio/vhost.c b/hw/virtio/vhost.c
index 30aee88..f7f7023 100644
--- a/hw/virtio/vhost.c
+++ b/hw/virtio/vhost.c
@@ -1214,17 +1214,17 @@ void vhost_dev_cleanup(struct vhost_dev *hdev)
int vhost_dev_enable_notifiers(struct vhost_dev *hdev, VirtIODevice *vdev)
{
BusState *qbus = BUS(qdev_get_parent_bus(DEVICE(vdev)));
- VirtioBusState *vbus = VIRTIO_BUS(qbus);
- VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(vbus);
int i, r, e;
- if (!k->ioeventfd_assign) {
+ /* We will pass the notifiers to the kernel, make sure that QEMU
+ * doesn't interfere.
+ */
+ r = virtio_device_grab_ioeventfd(vdev);
+ if (r < 0) {
error_report("binding does not support host notifiers");
- r = -ENOSYS;
goto fail;
}
- virtio_device_stop_ioeventfd(vdev);
for (i = 0; i < hdev->nvqs; ++i) {
r = virtio_bus_set_host_notifier(VIRTIO_BUS(qbus), hdev->vq_index + i,
true);
@@ -1244,7 +1244,7 @@ fail_vq:
}
assert (e >= 0);
}
- virtio_device_start_ioeventfd(vdev);
+ virtio_device_release_ioeventfd(vdev);
fail:
return r;
}
@@ -1267,7 +1267,7 @@ void vhost_dev_disable_notifiers(struct vhost_dev *hdev,
VirtIODevice *vdev)
}
assert (r >= 0);
}
- virtio_device_start_ioeventfd(vdev);
+ virtio_device_release_ioeventfd(vdev);
}
/* Test and clear event pending status.
diff --git a/hw/virtio/virtio-bus.c b/hw/virtio/virtio-bus.c
index bf61f66..d6c0c72 100644
--- a/hw/virtio/virtio-bus.c
+++ b/hw/virtio/virtio-bus.c
@@ -147,6 +147,39 @@ void virtio_bus_set_vdev_config(VirtioBusState *bus,
uint8_t *config)
}
}
+/* On success, ioeventfd ownership belongs to the caller. */
+int virtio_bus_grab_ioeventfd(VirtioBusState *bus)
+{
+ VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(bus);
+
+ /* vhost can be used even if ioeventfd=off in the proxy device,
+ * so do not check k->ioeventfd_enabled.
+ */
+ if (!k->ioeventfd_assign) {
+ return -ENOSYS;
+ }
+
+ if (bus->ioeventfd_grabbed == 0 && bus->ioeventfd_started) {
+ virtio_bus_stop_ioeventfd(bus);
+ /* Remember that we need to restart ioeventfd
+ * when ioeventfd_grabbed becomes zero.
+ */
+ bus->ioeventfd_started = true;
+ }
+ bus->ioeventfd_grabbed++;
+ return 0;
+}
+
+void virtio_bus_release_ioeventfd(VirtioBusState *bus)
+{
+ assert(bus->ioeventfd_grabbed != 0);
+ if (--bus->ioeventfd_grabbed == 0 && bus->ioeventfd_started) {
+ /* Force virtio_bus_start_ioeventfd to act. */
+ bus->ioeventfd_started = false;
+ virtio_bus_start_ioeventfd(bus);
+ }
+}
+
int virtio_bus_start_ioeventfd(VirtioBusState *bus)
{
VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(bus);
@@ -161,10 +194,14 @@ int virtio_bus_start_ioeventfd(VirtioBusState *bus)
if (bus->ioeventfd_started) {
return 0;
}
- r = vdc->start_ioeventfd(vdev);
- if (r < 0) {
- error_report("%s: failed. Fallback to userspace (slower).", __func__);
- return r;
+
+ /* Only set our notifier if we have ownership. */
+ if (!bus->ioeventfd_grabbed) {
+ r = vdc->start_ioeventfd(vdev);
+ if (r < 0) {
+ error_report("%s: failed. Fallback to userspace (slower).",
__func__);
+ return r;
+ }
}
bus->ioeventfd_started = true;
return 0;
@@ -179,9 +216,12 @@ void virtio_bus_stop_ioeventfd(VirtioBusState *bus)
return;
}
- vdev = virtio_bus_get_device(bus);
- vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
- vdc->stop_ioeventfd(vdev);
+ /* Only remove our notifier if we have ownership. */
+ if (!bus->ioeventfd_grabbed) {
+ vdev = virtio_bus_get_device(bus);
+ vdc = VIRTIO_DEVICE_GET_CLASS(vdev);
+ vdc->stop_ioeventfd(vdev);
+ }
bus->ioeventfd_started = false;
}
@@ -211,7 +251,6 @@ int virtio_bus_set_host_notifier(VirtioBusState *bus, int
n, bool assign)
}
if (assign) {
- assert(!bus->ioeventfd_started);
r = event_notifier_init(notifier, 1);
if (r < 0) {
error_report("%s: unable to init event notifier: %s (%d)",
@@ -225,9 +264,6 @@ int virtio_bus_set_host_notifier(VirtioBusState *bus, int
n, bool assign)
}
return 0;
} else {
- if (!bus->ioeventfd_started) {
- return 0;
- }
k->ioeventfd_assign(proxy, notifier, n, false);
}
diff --git a/hw/virtio/virtio.c b/hw/virtio/virtio.c
index 55a00cd..b7d5828 100644
--- a/hw/virtio/virtio.c
+++ b/hw/virtio/virtio.c
@@ -2191,6 +2191,22 @@ void virtio_device_stop_ioeventfd(VirtIODevice *vdev)
virtio_bus_stop_ioeventfd(vbus);
}
+int virtio_device_grab_ioeventfd(VirtIODevice *vdev)
+{
+ BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
+ VirtioBusState *vbus = VIRTIO_BUS(qbus);
+
+ return virtio_bus_grab_ioeventfd(vbus);
+}
+
+void virtio_device_release_ioeventfd(VirtIODevice *vdev)
+{
+ BusState *qbus = qdev_get_parent_bus(DEVICE(vdev));
+ VirtioBusState *vbus = VIRTIO_BUS(qbus);
+
+ virtio_bus_release_ioeventfd(vbus);
+}
+
static void virtio_device_class_init(ObjectClass *klass, void *data)
{
/* Set the default value here. */
diff --git a/include/hw/virtio/virtio-bus.h b/include/hw/virtio/virtio-bus.h
index fdf7fda..8a51e2c 100644
--- a/include/hw/virtio/virtio-bus.h
+++ b/include/hw/virtio/virtio-bus.h
@@ -97,6 +97,16 @@ struct VirtioBusState {
* Set if ioeventfd has been started.
*/
bool ioeventfd_started;
+
+ /*
+ * Set if ioeventfd has been grabbed by vhost. When ioeventfd
+ * is grabbed by vhost, we track its started/stopped state (which
+ * depends in turn on the virtio status register), but do not
+ * register a handler for the ioeventfd. When ioeventfd is
+ * released, if ioeventfd_started is true we finally register
+ * the handler so that QEMU's device model can use ioeventfd.
+ */
+ int ioeventfd_grabbed;
};
void virtio_bus_device_plugged(VirtIODevice *vdev, Error **errp);
@@ -131,6 +141,10 @@ bool virtio_bus_ioeventfd_enabled(VirtioBusState *bus);
int virtio_bus_start_ioeventfd(VirtioBusState *bus);
/* Stop the ioeventfd. */
void virtio_bus_stop_ioeventfd(VirtioBusState *bus);
+/* Tell the bus that vhost is grabbing the ioeventfd. */
+int virtio_bus_grab_ioeventfd(VirtioBusState *bus);
+/* bus that vhost is not using the ioeventfd anymore. */
+void virtio_bus_release_ioeventfd(VirtioBusState *bus);
/* Switch from/to the generic ioeventfd handler */
int virtio_bus_set_host_notifier(VirtioBusState *bus, int n, bool assign);
diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h
index 5951997..835b085 100644
--- a/include/hw/virtio/virtio.h
+++ b/include/hw/virtio/virtio.h
@@ -272,6 +272,8 @@ void virtio_queue_set_guest_notifier_fd_handler(VirtQueue
*vq, bool assign,
bool with_irqfd);
int virtio_device_start_ioeventfd(VirtIODevice *vdev);
void virtio_device_stop_ioeventfd(VirtIODevice *vdev);
+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_host_notifier_read(EventNotifier *n);
--
generated by git-patchbot for /home/xen/git/qemu-xen.git#master
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