Re: [PATCH 06/12] xen: generate hypercall interface related code

[Jan Beulich <jbeulich@xxxxxxxx>]

On 18.10.2021 17:28, Juergen Gross wrote:
> On 18.10.21 14:58, Jan Beulich wrote:
>> On 15.10.2021 14:51, Juergen Gross wrote:
>>> Instead of repeating similar data multiple times use a single source
>>> file and a generator script for producing prototypes and call sequences
>>> of the hypercalls.
>>>
>>> As the script already knows the number of parameters used add generating
>>> a macro for populating an array with the number of parameters per
>>> hypercall.
>>
>> Isn't that array intended to go away?
> 
> I thought so, yes, but on Arm there is a case where it is needed.
> 
> So generating it from the available data is the sensible thing to do
> IMO.

Absolutely, if such a table continues to be needed.

>>> @@ -466,6 +468,14 @@ include/asm-$(TARGET_ARCH)/asm-offsets.h: asm-offsets.s
>>>       echo ""; \
>>>       echo "#endif") <$< >$@
>>>   
>>> +quiet_cmd_genhyp = GEN     $@
>>> +define cmd_genhyp
>>> +    awk -f scripts/gen_hypercall.awk <$< >$@
>>> +endef
>>> +
>>> +include/xen/hypercall-defs.h: include/hypercall-defs.i 
>>> scripts/gen_hypercall.awk FORCE
>>> +   $(call if_changed,genhyp)
>>
>> As per patch 5 there are quite a few sources including xen/hypercall.h
>> and hence (in one of the next patches) the header generated here. If
>> this one gets re-generated for a benign reason (i.e. without changing
>> the header), all dependents will get rebuilt for no reason. Use
>> $(move-if-changed ...)?
> 
> The reasons for re-generating are quite limited. The most probable case
> is a .config change, which will trigger quite some rebuild anyway.

Oh, good point - I should also have considered the dependencies here,
which are pretty limited. Please disregard my remark then.

Jan