Re: [Qemu-devel] [PATCH RFC 2/4] qdev/machine: Introduce hotplug_allowed hook

[Auger Eric <eric.auger@redhat.com>]

Hi Peter,

On 8/12/19 9:45 AM, Peter Xu wrote:
> Introduce this new per-machine hook to give any machine class a chance
> to do a sanity check on the to-be-hotplugged device as a sanity test.
> This will be used for x86 to try to detect some illegal configuration
> of devices, e.g., possible conflictions between vfio-pci and x86
conflicts
> vIOMMU.
> 
> Signed-off-by: Peter Xu <peterx@redhat.com>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric
> ---
>  hw/core/qdev.c         | 17 +++++++++++++++++
>  include/hw/boards.h    |  9 +++++++++
>  include/hw/qdev-core.h |  1 +
>  qdev-monitor.c         |  7 +++++++
>  4 files changed, 34 insertions(+)
> 
> diff --git a/hw/core/qdev.c b/hw/core/qdev.c
> index 94ebc0a4a1..d792b43c37 100644
> --- a/hw/core/qdev.c
> +++ b/hw/core/qdev.c
> @@ -236,6 +236,23 @@ HotplugHandler *qdev_get_machine_hotplug_handler(DeviceState *dev)
>      return NULL;
>  }
>  
> +bool qdev_hotplug_allowed(DeviceState *dev, Error **errp)
> +{
> +    MachineState *machine;
> +    MachineClass *mc;
> +    Object *m_obj = qdev_get_machine();
> +
> +    if (object_dynamic_cast(m_obj, TYPE_MACHINE)) {
> +        machine = MACHINE(m_obj);
> +        mc = MACHINE_GET_CLASS(machine);
> +        if (mc->hotplug_allowed) {
> +            return mc->hotplug_allowed(machine, dev, errp);
> +        }
> +    }
> +
> +    return true;
> +}
> +
>  HotplugHandler *qdev_get_bus_hotplug_handler(DeviceState *dev)
>  {
>      if (dev->parent_bus) {
> diff --git a/include/hw/boards.h b/include/hw/boards.h
> index a71d1a53a5..1cf63be45d 100644
> --- a/include/hw/boards.h
> +++ b/include/hw/boards.h
> @@ -166,6 +166,13 @@ typedef struct {
>   *    The function pointer to hook different machine specific functions for
>   *    parsing "smp-opts" from QemuOpts to MachineState::CpuTopology and more
>   *    machine specific topology fields, such as smp_dies for PCMachine.
> + * @hotplug_allowed:
> + *    If the hook is provided, then it'll be called for each device
> + *    hotplug to check whether the device hotplug is allowed.  Return
> + *    true to grant allowance or false to reject the hotplug.  When
> + *    false is returned, an error must be set to show the reason of
> + *    the rejection.  If the hook is not provided, all hotplug will be
> + *    allowed.
>   */
>  struct MachineClass {
>      /*< private >*/
> @@ -223,6 +230,8 @@ struct MachineClass {
>  
>      HotplugHandler *(*get_hotplug_handler)(MachineState *machine,
>                                             DeviceState *dev);
> +    bool (*hotplug_allowed)(MachineState *state, DeviceState *dev,
> +                            Error **errp);
>      CpuInstanceProperties (*cpu_index_to_instance_props)(MachineState *machine,
>                                                           unsigned cpu_index);
>      const CPUArchIdList *(*possible_cpu_arch_ids)(MachineState *machine);
> diff --git a/include/hw/qdev-core.h b/include/hw/qdev-core.h
> index 136df7774c..88e7ec4b60 100644
> --- a/include/hw/qdev-core.h
> +++ b/include/hw/qdev-core.h
> @@ -284,6 +284,7 @@ void qdev_set_legacy_instance_id(DeviceState *dev, int alias_id,
>                                   int required_for_version);
>  HotplugHandler *qdev_get_bus_hotplug_handler(DeviceState *dev);
>  HotplugHandler *qdev_get_machine_hotplug_handler(DeviceState *dev);
> +bool qdev_hotplug_allowed(DeviceState *dev, Error **errp);
>  /**
>   * qdev_get_hotplug_handler: Get handler responsible for device wiring
>   *
> diff --git a/qdev-monitor.c b/qdev-monitor.c
> index 58222c2211..6c80602771 100644
> --- a/qdev-monitor.c
> +++ b/qdev-monitor.c
> @@ -614,6 +614,13 @@ DeviceState *qdev_device_add(QemuOpts *opts, Error **errp)
>      /* create device */
>      dev = DEVICE(object_new(driver));
>  
> +    /* Check whether the hotplug is allowed by the machine */
> +    if (qdev_hotplug && !qdev_hotplug_allowed(dev, &err)) {
> +        /* Error must be set in the machine hook */
> +        assert(err);
> +        goto err_del_dev;
> +    }
> +
>      if (bus) {
>          qdev_set_parent_bus(dev, bus);
>      } else if (qdev_hotplug && !qdev_get_machine_hotplug_handler(dev)) {
>