Re: [Qemu-devel] [qemu RFC] qapi: add "firmware.json"

[Thomas Huth]

On 10.04.2018 11:05, Daniel P. Berrangé wrote:
> On Mon, Apr 09, 2018 at 06:34:41PM +0200, Laszlo Ersek wrote:
>> On 04/09/18 09:26, Thomas Huth wrote:
>>>  Hi Laszlo,
>>>
>>> On 07.04.2018 02:01, Laszlo Ersek wrote:
>>>> Add a schema that describes the properties of virtual machine firmware.
>>>>
>>>> Each firmware executable installed on a host system should come with a
>>>> JSON file that conforms to this schema, and informs the management
>>>> applications about the firmware's properties.
>>>>
>>>> In addition, a configuration directory with symlinks to the JSON files
>>>> should exist, with the symlinks carefully named to reflect a priority
>>>> order. Management applications can then search this directory in priority
>>>> order for the first firmware executable that satisfies their search
>>>> criteria. The found JSON file provides the management layer with domain
>>>> configuration bits that are required to run the firmware binary.
>>> [...]
>>>> +##
>>>> +# @FirmwareDevice:
>>>> +#
>>>> +# Defines the device types that a firmware file can be mapped into.
>>>> +#
>>>> +# @memory: The firmware file is to be mapped into memory.
>>>> +#
>>>> +# @kernel: The firmware file is to be loaded like a Linux kernel. This is
>>>> +#          similar to @memory but may imply additional processing that is
>>>> +#          specific to the target architecture.
>>>> +#
>>>> +# @flash: The firmware file is to be mapped into a pflash chip.
>>>> +#
>>>> +# Since: 2.13
>>>> +##
>>>> +{ 'enum' : 'FirmwareDevice',
>>>> +  'data' : [ 'memory', 'kernel', 'flash' ] }
>>>
>>> This is not fully clear to me... what is this exactly good for? Is this
>>> a way to say how the firmware should be loaded, i.e. via "-bios",
>>> "-kernel" or "-pflash" parameter? If so, the term "memory" is quite
>>> misleading since files that are loaded via -bios can also end up in an
>>> emulated ROM chip.
>>
>> I threw in "-kernel" because, although it also (usually?) means
>> "memory", I expected people would want it separate.
> 
> What platform / scenario actually uses -kernel to load firmware.

I think uboot uses -kernel in certain cases, see e.g.:

https://balau82.wordpress.com/2010/03/10/u-boot-for-arm-on-qemu/

> If you
> have loaded firmware using -kernel, how do you then load the actual
> kernel ?

The kernel is then loaded from disk or network or another boot device.

 Thomas