Re: [PATCH v5 04/13] xen/arm64: Split and move MMU-specific head.S to mmu/head.S

[Julien Grall <julien@xxxxxxx>]

On 21/08/2023 10:29, Henry Wang wrote:
> > On Aug 21, 2023, at 17:18, Julien Grall <julien@xxxxxxx> wrote:
> > On 14/08/2023 05:25, Henry Wang wrote:
> > > The MMU specific code in head.S will not be used on MPU systems.
> > > Instead of introducing more #ifdefs which will bring complexity
> > > to the code, move MMU related code to mmu/head.S and keep common
> > > code in head.S. Two notes while moving:
> > > - As "fail" in original head.S is very simple and this name is too
> > >    easy to be conflicted, duplicate it in mmu/head.S instead of
> > >    exporting it.
> > > - Use ENTRY() for enable_secondary_cpu_mm, enable_boot_cpu_mm and
> > >    setup_fixmap to please the compiler after the code movement.
> > I am not sure I understand why you are saying "to please the compiler" here. 
> > Isn't it necessary for the linker (not the compiler) to find the function? And therefore 
> > there is no pleasing (as in this is not a bug in the toolchain).
> Yes it meant to be linker, sorry for the confusion. What I want to express is
> without the ENTRY(), for example if we remove the ENTRY() around the
> setup_fixmap(), we will have:
>
> ```
> aarch64-none-linux-gnu-ld: prelink.o: in function `primary_switched':
> /home/xinwan02/repos_for_development/xen_playground/xen/xen/arch/arm/arm64/head.S:278:
>  undefined reference to `setup_fixmap'
> /home/xinwan02/repos_for_development/xen_playground/xen/xen/arch/arm/arm64/head.S:278:(.text.header+0x1a0):
>  relocation truncated to fit: R_AARCH64_CALL26 against undefined symbol 
> `setup_fixmap'
> make[2]: *** [arch/arm/Makefile:95: xen-syms] Error 1
> make[1]: *** [build.mk:90: xen] Error 2
> make: *** [Makefile:598: xen] Error 2
> ```
>
> I will use the word “linker” in v6 if you agree.
The sentence also need to be reworded. How about:

"Use ENTRY() for ... as they will be used externally."

> > Other than that, the split looks good to me.
> May I please take this as a Reviewed-by tag? I will add the tag if you are
> happy with that.
Sure. Reviewed-by: Julien Grall <jgrall@xxxxxxxxxx>

Cheers,

--
Julien Grall