Re: [RFC PATCH 04/18] qemu: Introduce 'qemu/legacy_binary_info.h'

["Philippe Mathieu-Daudé" <philmd@linaro.org>]

On 6/3/25 08:26, Thomas Huth wrote:
> On 05/03/2025 17.59, Pierrick Bouvier wrote:
>> On 3/5/25 07:39, Philippe Mathieu-Daudé wrote:
>>> Introduce an API to get information specific to a binary
>>> from the binary name (argv[0]).
>>>
>>> Initialize it from qemu_init() on system emulation.
>>>
>>
>> What we want here is more a include/qemu/target_info.h, which will 
>> allow to query the name of it, and helper for every architecture:
>>
>> target_is_aarch64()
>> target_is_ppc64()
>> ...
>>
>> Eventually, we can add combined getters like:
>> target_is_64bit()
>> ...
>>
>> Naming "legacy" something that will be present in the long term is not 
>> the best move I think.
> 
> FWIW, I agree, this should rather be target_is_64bit() or something 
> similar, like target_words_bigendian() ?

This API is to allow refactoring code for heterogeneous emulation,
without changing user-facing behavior of current qemu-system binaries,
which I now consider as 'legacy'.

Once all current restrictions removed, the new qemu-system-heterogeneous
binary is expected to run any combination of targets.

qemu-system-$target will be a call to qemu-system-heterogeneous with
a restricted subset, possibly in the form of:

  $ qemu-system-heterogeneous --target aarch64-softmmu

    ^ equivalent of today's qemu-system-aarch64

If you don't like 'qemu_legacy_binary_' prefix, I can use
'qemu_single_binary_' instead.


target_is_64bit() is misleading, for example in:

  $ qemu-system-aarch64 -M zynqmp

we create 64-bit and 32-bit ARM cores.