On Wed, Apr 22, 2020 at 12:17:50PM -0400, Raphael Norwitz wrote:
> There are some problems with this patch. It doesn't apply cleanly.
>
> Are you sure you’re developing on an up to date master branch?
>
> On Thu, Apr 23, 2020 at 09:39:36PM +0300, Dima Stepanov wrote:
> >
> > In case of the vhost-user devices the daemon can be killed at any
> > moment. Since QEMU supports the reconnet functionality the guest
> > notifiers should be reset and disabled after "disconnect" event. The
> > most issues were found if the "disconnect" event happened during vhost
> > device initialization step.
> > The disconnect event leads to the call of the vhost_dev_cleanup()
> > routine. Which memset to 0 a vhost device structure. Because of this, if
> > device was not started (dev.started == false) and the connection is
> > broken, then the set_guest_notifier method will produce assertion error.
> > Also connection can be broken after the dev.started field is set to
> > true.
> > A new notifiers_set field is added to the vhost_dev structure to track
> > the state of the guest notifiers during the initialization process.
> >
> > Signed-off-by: Dima Stepanov <dimas...@yandex-team.ru>
> > ---
> > hw/block/vhost-user-blk.c | 8 ++++----
> > hw/virtio/vhost.c | 11 +++++++++++
> > include/hw/virtio/vhost.h | 1 +
> > 3 files changed, 16 insertions(+), 4 deletions(-)
> >
> > @@ -1417,6 +1422,8 @@ void vhost_dev_disable_notifiers(struct vhost_dev
> > *hdev, VirtIODevice *vdev)
>
> I can’t find the function vhost_dev_drop_guest_notifiers() in
> /hw/virtio/vhost.c, or anywhere in the codebase.
>
> Where does this code come from?
These wrapper functions were introduced in this patch set with the
previous patch:
[RFC PATCH v1 4/7] vhost: introduce wrappers to set guest notifiers for
virtio device
The problem was found in the vhost-user-blk stack. But it seems to me
that it is the same for all vhost-user devices. That is why i've tried
to suggest solution which will resolve other vhost-user devices, too.
And this was the reason to add new wrappers.
>
> > virtio_bus_cleanup_host_notifier(VIRTIO_BUS(qbus), hdev->vq_index
> > + i);
> > }
> > virtio_device_release_ioeventfd(vdev);
> > +
> > + hdev->notifiers_set = false;
> > }
> >
> > /*
> > @@ -1449,6 +1456,10 @@ int vhost_dev_drop_guest_notifiers(struct vhost_dev
> > *hdev,
> > VirtioBusClass *k = VIRTIO_BUS_GET_CLASS(qbus);
> > int ret;
> >
> > + if (!hdev->notifiers_set) {
> > + return 0;
> > + }
> > +
> > ret = k->set_guest_notifiers(qbus->parent, nvqs, false);
> > if (ret < 0) {
> > error_report("Error reset guest notifier: %d", -ret);
> > diff --git a/include/hw/virtio/vhost.h b/include/hw/virtio/vhost.h
> > index 4d0d2e2..e3711a7 100644
> > --- a/include/hw/virtio/vhost.h
> > +++ b/include/hw/virtio/vhost.h
> > @@ -90,6 +90,7 @@ struct vhost_dev {
> > QLIST_HEAD(, vhost_iommu) iommu_list;
> > IOMMUNotifier n;
> > const VhostDevConfigOps *config_ops;
> > + bool notifiers_set;
> > };
> >
> > int vhost_dev_init(struct vhost_dev *hdev, void *opaque,
> > --
> > 2.7.4
> >
> >
