Re: [Qemu-devel] [PATCH v2 2/2] hw/acpi/vmgenid: prevent more than one vmgenid device

[Igor Mammedov]

On Mon, 20 Mar 2017 18:05:57 +0100
Laszlo Ersek <address@hidden> wrote:

> A system with multiple VMGENID devices is undefined in the VMGENID spec by
> omission.
> 
> Cc: "Michael S. Tsirkin" <address@hidden>
> Cc: Ben Warren <address@hidden>
> Cc: Igor Mammedov <address@hidden>
> Cc: Paolo Bonzini <address@hidden>
> Signed-off-by: Laszlo Ersek <address@hidden>
Reviewed-by: Igor Mammedov <address@hidden>

> ---
> 
> Notes:
>     v2:
>     - use find_vmgenid_dev() rather than open-code
>       object_resolve_path_type() [Michael]
>     - add comments to both the definition of find_vmgenid_dev() and its call
>       site in vmgenid_realize() [Michael]
> 
>  include/hw/acpi/vmgenid.h | 1 +
>  hw/acpi/vmgenid.c         | 8 ++++++++
>  2 files changed, 9 insertions(+)
> 
> diff --git a/include/hw/acpi/vmgenid.h b/include/hw/acpi/vmgenid.h
> index 8578476baebe..7beb9592fb01 100644
> --- a/include/hw/acpi/vmgenid.h
> +++ b/include/hw/acpi/vmgenid.h
> @@ -24,6 +24,7 @@ typedef struct VmGenIdState {
>      bool write_pointer_available;
>  } VmGenIdState;
>  
> +/* returns NULL unless there is exactly one device */
>  static inline Object *find_vmgenid_dev(void)
>  {
>      return object_resolve_path_type("", VMGENID_DEVICE, NULL);
> diff --git a/hw/acpi/vmgenid.c b/hw/acpi/vmgenid.c
> index c3ddcc8e7cb0..a32b847fe0df 100644
> --- a/hw/acpi/vmgenid.c
> +++ b/hw/acpi/vmgenid.c
> @@ -221,6 +221,14 @@ static void vmgenid_realize(DeviceState *dev, Error 
> **errp)
>          return;
>      }
>  
> +    /* Given that this function is executing, there is at least one VMGENID
> +     * device. Check if there are several.
> +     */
> +    if (!find_vmgenid_dev()) {
> +        error_setg(errp, "at most one %s device is permitted", 
> VMGENID_DEVICE);
> +        return;
> +    }
> +
>      qemu_register_reset(vmgenid_handle_reset, vms);
>  }
>