On Tue, 18 Jun 2024 15:19, Thomas Huth <th...@redhat.com> 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
virtio_device_should_start() returning true if it's already started and
running looks like a code smell to me... it intuitively feels like a
ternary state instead of boolean: not startable, startable, already
started.
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>
---
Reviewed-by: Manos Pitsidianakis <manos.pitsidiana...@linaro.org>
