Re: [PATCH] device-tree: Move Arm's static-evtchn feature to common

["Orzel, Michal" <michal.orzel@xxxxxxx>]

On 03/06/2025 09:02, Jan Beulich wrote:
> On 03.06.2025 08:54, Orzel, Michal wrote:
>>
>>
>> On 02/06/2025 10:37, Jan Beulich wrote:
>>> On 27.05.2025 10:21, Michal Orzel wrote:
>>>> There's nothing Arm specific about this feature. Move it to common as
>>>> part of a larger activity to commonalize device tree related features.
>>>> For now, select it only for ARM until others (e.g. RISC-V) verify it
>>>> works for them too.
>>>>
>>>> Signed-off-by: Michal Orzel <michal.orzel@xxxxxxx>
>>>
>>> I realize this was already committed, but ...
>>>
>>>> --- a/xen/common/Kconfig
>>>> +++ b/xen/common/Kconfig
>>>> @@ -162,6 +162,14 @@ config STATIC_MEMORY
>>>>  
>>>>      If unsure, say N.
>>>>  
>>>> +config STATIC_EVTCHN
>>>> +  bool "Static event channel support on a dom0less system"
>>>> +  depends on DOM0LESS_BOOT && ARM
>>>
>>> ... I think we should strive to avoid such arch dependencies; they simply
>>> don't scale very well. Instead (if needed) HAS_* should be introduced, which
>>> each interested arch can select. In the case here, however, perhaps
>>> DOM0LESS_BOOT alone would have been sufficient as a dependency?
>> What if e.g. RISC-V wants to enable dom0less but not static 
>> evtchn/memory/shmem
>> because there are some functions to be implemented and they don't want to do 
>> it
>> now? Protecting with just DOM0LESS_BOOT would not be sufficient here.
> 
> Imo a transient(!) "depends on !RISCV" would in principle be fine, if ...
In this case, how can I know that upfront? When moving a feature I need to put
some dependencies. At that point I don't know RISCV, PPC plans. The only thing I
know is that I tested this feature on Arm. So the only meaningful dependency is
& ARM.

~Michal