Re: [Qemu-devel] [PATCH v3 2/2] qdev: Check for the availability of a hotplug controller before adding a device

[Cornelia Huck <cohuck@redhat.com>]

On Thu,  2 Nov 2017 11:10:06 +0100
Thomas Huth <thuth@redhat.com> wrote:

> The qdev_unplug() function contains a g_assert(hotplug_ctrl) statement,
> so QEMU crashes when the user tries to device_add + device_del a device
> that does not have a corresponding hotplug controller. This could be
> provoked for a couple of devices in the past (see commit 4c93950659487c7ad
> or 84ebd3e8c7d4fe955 for example), and can currently for example also be
> triggered like this:
> 
> $ s390x-softmmu/qemu-system-s390x -M none -nographic 
> QEMU 2.10.50 monitor - type 'help' for more information
> (qemu) device_add qemu-s390x-cpu,id=x
> (qemu) device_del x
> **
> ERROR:qemu/qdev-monitor.c:872:qdev_unplug: assertion failed: (hotplug_ctrl)
> Aborted (core dumped)
> 
> So devices clearly need a hotplug controller when they should be usable
> with device_add.
> The code in qdev_device_add() already checks whether the bus has a proper
> hotplug controller, but for devices that do not have a corresponding bus,
> there is no appropriate check available yet. In that case we should check
> whether the machine itself provides a suitable hotplug controller and
> refuse to plug the device if none is available.
> 
> Reviewed-by: Igor Mammedov <imammedo@redhat.com>
> Signed-off-by: Thomas Huth <thuth@redhat.com>
> ---
>  hw/core/qdev.c         | 28 ++++++++++++++++++++--------
>  include/hw/qdev-core.h |  1 +
>  qdev-monitor.c         |  5 +++++
>  3 files changed, 26 insertions(+), 8 deletions(-)

Reviewed-by: Cornelia Huck <cohuck@redhat.com>