Re: [PATCH for-6.0 2/4] machine: Provide a function to check the dynamic sysbus whitelist

[Auger Eric]

Hi Peter,

On 3/25/21 4:33 PM, Peter Maydell wrote:
> Provide a new function dynamic_sysbus_dev_allowed() which checks
> the per-machine whitelist of dynamic sysbus devices and returns
> a boolean result indicating whether the device is whitelisted.
> We can use this in the implementation of validate_sysbus_device(),
> but we will also need it so that machine hotplug callbacks can
> validate devices rather than assuming that any sysbus device
> might be hotpluggable into the platform bus.
> 
> Signed-off-by: Peter Maydell <peter.maydell@linaro.org>
Reviewed-by: Eric Auger <eric.auger@redhat.com>

Thanks

Eric

> ---
>  include/hw/boards.h | 24 ++++++++++++++++++++++++
>  hw/core/machine.c   | 21 ++++++++++++++++-----
>  2 files changed, 40 insertions(+), 5 deletions(-)
> 
> diff --git a/include/hw/boards.h b/include/hw/boards.h
> index 27106abc11d..609112a4e1a 100644
> --- a/include/hw/boards.h
> +++ b/include/hw/boards.h
> @@ -51,6 +51,30 @@ void machine_set_cpu_numa_node(MachineState *machine,
>   */
>  void machine_class_allow_dynamic_sysbus_dev(MachineClass *mc, const char 
> *type);
>  
> +/**
> + * device_is_dynamic_sysbus: test whether device is a dynamic sysbus device
> + * @mc: Machine class
> + * @dev: device to check
> + *
> + * Returns: true if @dev is a sysbus device on the machine's whitelist
> + * of dynamically pluggable sysbus devices; otherwise false.
> + *
> + * This function checks whether @dev is a valid dynamic sysbus device,
> + * by first confirming that it is a sysbus device and then checking it
> + * against the whitelist of permitted dynamic sysbus devices which has
> + * been set up by the machine using machine_class_allow_dynamic_sysbus_dev().
> + *
> + * It is valid to call this with something that is not a subclass of
> + * TYPE_SYS_BUS_DEVICE; the function will return false in this case.
> + * This allows hotplug callback functions to be written as:
> + *     if (device_is_dynamic_sysbus(mc, dev)) {
> + *         handle dynamic sysbus case;
> + *     } else if (some other kind of hotplug) {
> + *         handle that;
> + *     }
> + */
> +bool device_is_dynamic_sysbus(MachineClass *mc, DeviceState *dev);
> +
>  /*
>   * Checks that backend isn't used, preps it for exclusive usage and
>   * returns migratable MemoryRegion provided by backend.
> diff --git a/hw/core/machine.c b/hw/core/machine.c
> index 9935c6ddd56..8d97094736a 100644
> --- a/hw/core/machine.c
> +++ b/hw/core/machine.c
> @@ -529,20 +529,31 @@ void 
> machine_class_allow_dynamic_sysbus_dev(MachineClass *mc, const char *type)
>      QAPI_LIST_PREPEND(mc->allowed_dynamic_sysbus_devices, g_strdup(type));
>  }
>  
> -static void validate_sysbus_device(SysBusDevice *sbdev, void *opaque)
> +bool device_is_dynamic_sysbus(MachineClass *mc, DeviceState *dev)
>  {
> -    MachineState *machine = opaque;
> -    MachineClass *mc = MACHINE_GET_CLASS(machine);
>      bool allowed = false;
>      strList *wl;
> +    Object *obj = OBJECT(dev);
> +
> +    if (!object_dynamic_cast(obj, TYPE_SYS_BUS_DEVICE)) {
> +        return false;
> +    }
>  
>      for (wl = mc->allowed_dynamic_sysbus_devices;
>           !allowed && wl;
>           wl = wl->next) {
> -        allowed |= !!object_dynamic_cast(OBJECT(sbdev), wl->value);
> +        allowed |= !!object_dynamic_cast(obj, wl->value);
>      }
>  
> -    if (!allowed) {
> +    return allowed;
> +}
> +
> +static void validate_sysbus_device(SysBusDevice *sbdev, void *opaque)
> +{
> +    MachineState *machine = opaque;
> +    MachineClass *mc = MACHINE_GET_CLASS(machine);
> +
> +    if (!device_is_dynamic_sysbus(mc, DEVICE(sbdev))) {
>          error_report("Option '-device %s' cannot be handled by this machine",
>                       object_class_get_name(object_get_class(OBJECT(sbdev))));
>          exit(1);
>