Re: [Qemu-devel] [PATCH 2/2] hw/acpi/vmgenid: prevent more than one vmgenid device

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Mar 20, 2017 at 12:59:51PM +0100, Laszlo Ersek wrote:
> Multiple instances make no sense.
> 
> Cc: "Michael S. Tsirkin" <mst@redhat.com>
> Cc: Ben Warren <ben@skyportsystems.com>
> Cc: Igor Mammedov <imammedo@redhat.com>
> Signed-off-by: Laszlo Ersek <lersek@redhat.com>

find_vmgenid_dev would be a better place for this.
This is where the single instance assumption comes from ATM.


> ---
>  hw/acpi/vmgenid.c | 10 ++++++++++
>  1 file changed, 10 insertions(+)
> 
> diff --git a/hw/acpi/vmgenid.c b/hw/acpi/vmgenid.c
> index c3ddcc8e7cb0..b5c0dfcf19e1 100644
> --- a/hw/acpi/vmgenid.c
> +++ b/hw/acpi/vmgenid.c
> @@ -214,6 +214,8 @@ static Property vmgenid_properties[] = {
>  static void vmgenid_realize(DeviceState *dev, Error **errp)
>  {
>      VmGenIdState *vms = VMGENID(dev);
> +    Object *one_vmgenid;
> +    bool ambiguous;
>  
>      if (!vms->write_pointer_available) {
>          error_setg(errp, "%s requires DMA write support in fw_cfg, "
> @@ -221,6 +223,14 @@ static void vmgenid_realize(DeviceState *dev, Error **errp)
>          return;
>      }
>  
> +    one_vmgenid = object_resolve_path_type("", VMGENID_DEVICE, &ambiguous);
> +    if (one_vmgenid == NULL) {
> +        assert(ambiguous);
> +        error_setg(errp, "at most one %s device is permitted", VMGENID_DEVICE);
> +        return;
> +    }
> +    assert(one_vmgenid == OBJECT(vms));
> +
>      qemu_register_reset(vmgenid_handle_reset, vms);
>  }
>  
> -- 
> 2.9.3