On Mon, Jul 01, 2024 at 04:07:56PM +0200, Thomas Huth wrote: > On 18/06/2024 14.19, Thomas Huth wrote: > > The unrealize functions of the various vhost-user devices are > > calling the corresponding vhost_*_set_status() functions with a > > status of 0 to shut down the device correctly. > > > > Now these vhost_*_set_status() functions all follow this scheme: > > > > bool should_start = virtio_device_should_start(vdev, status); > > > > if (vhost_dev_is_started(&vvc->vhost_dev) == should_start) { > > return; > > } > > > > if (should_start) { > > /* ... do the initialization stuff ... */ > > } else { > > /* ... do the cleanup stuff ... */ > > } > > > > The problem here is virtio_device_should_start(vdev, 0) currently > > always returns "true" since it internally only looks at vdev->started > > instead of looking at the "status" parameter. Thus once the device > > got started once, virtio_device_should_start() always returns true > > and thus the vhost_*_set_status() functions return early, without > > ever doing any clean-up when being called with status == 0. This > > causes e.g. problems when trying to hot-plug and hot-unplug a vhost > > user devices multiple times since the de-initialization step is > > completely skipped during the unplug operation. > > > > This bug has been introduced in commit 9f6bcfd99f ("hw/virtio: move > > vm_running check to virtio_device_started") which replaced > > > > should_start = status & VIRTIO_CONFIG_S_DRIVER_OK; > > > > with > > > > should_start = virtio_device_started(vdev, status); > > > > which later got replaced by virtio_device_should_start(). This blocked > > the possibility to set should_start to false in case the status flag > > VIRTIO_CONFIG_S_DRIVER_OK was not set. > > > > Fix it by adjusting the virtio_device_should_start() function to > > only consider the status flag instead of vdev->started. Since this > > function is only used in the various vhost_*_set_status() functions > > for exactly the same purpose, it should be fine to fix it in this > > central place there without any risk to change the behavior of other > > code. > > > > Fixes: 9f6bcfd99f ("hw/virtio: move vm_running check to > > virtio_device_started") > > Buglink: https://issues.redhat.com/browse/RHEL-40708 > > Signed-off-by: Thomas Huth <th...@redhat.com> > > --- > > include/hw/virtio/virtio.h | 8 ++++---- > > 1 file changed, 4 insertions(+), 4 deletions(-) > > > > diff --git a/include/hw/virtio/virtio.h b/include/hw/virtio/virtio.h > > index 7d5ffdc145..2eafad17b8 100644 > > --- a/include/hw/virtio/virtio.h > > +++ b/include/hw/virtio/virtio.h > > @@ -470,9 +470,9 @@ static inline bool virtio_device_started(VirtIODevice > > *vdev, uint8_t status) > > * @vdev - the VirtIO device > > * @status - the devices status bits > > * > > - * This is similar to virtio_device_started() but also encapsulates a > > - * check on the VM status which would prevent a device starting > > - * anyway. > > + * This is similar to virtio_device_started() but ignores vdev->started > > + * and also encapsulates a check on the VM status which would prevent a > > + * device from starting anyway. > > */ > > static inline bool virtio_device_should_start(VirtIODevice *vdev, uint8_t > > status) > > { > > @@ -480,7 +480,7 @@ static inline bool > > virtio_device_should_start(VirtIODevice *vdev, uint8_t status > > return false; > > } > > - return virtio_device_started(vdev, status); > > + return status & VIRTIO_CONFIG_S_DRIVER_OK; > > } > > Michael, any concerns or comments about this patch? > > If not, I could also take it via my s390x tree since this fixes vhost-ccw > devices on s390x. > > Thomas
I'm working on a pull request with this today. I can drop it if you prefer ...