RE: [PATCH 20/37] xen: introduce CONFIG_EFI to stub API for non-EFI architecture

[Wei Chen <Wei.Chen@xxxxxxx>]

Hi Julien,

> -----Original Message-----
> From: Julien Grall <julien@xxxxxxx>
> Sent: 2022年1月27日 18:01
> To: Jan Beulich <jbeulich@xxxxxxxx>; Wei Chen <Wei.Chen@xxxxxxx>
> Cc: Bertrand Marquis <Bertrand.Marquis@xxxxxxx>; xen-
> devel@xxxxxxxxxxxxxxxxxxxx; sstabellini@xxxxxxxxxx
> Subject: Re: [PATCH 20/37] xen: introduce CONFIG_EFI to stub API for non-
> EFI architecture
> 
> Hi,
> 
> On 27/01/2022 09:27, Jan Beulich wrote:
> > On 27.01.2022 10:25, Wei Chen wrote:
> >>> From: Jan Beulich <jbeulich@xxxxxxxx>
> >>> Sent: 2022年1月27日 17:17
> >>>
> >>> On 27.01.2022 10:09, Wei Chen wrote:
> >>>>> From: Jan Beulich <jbeulich@xxxxxxxx>
> >>>>> Sent: 2022年1月27日 17:00
> >>>>>
> >>>>> But you realize we already have such a stub file on x86?
> >>>>>
> >>>>
> >>>> Yes, we found the redefinition errors that are caused by x86 stub
> file
> >>>> and new macros in stub.h. We had tries to add:
> >>>> ifeq ($(XEN_BUILD_EFI),y)
> >>>> CFLAGS-y += -DXEN_BUILD_EFI
> >>>> XEN_CFLAGS += -DXEN_BUILD_EFI
> >>>> endif
> >>>> x86/Makefile to gate these new macros, but it seems that we may need
> >>>> to change EFI build logic for x86. It will cause more risks for me.
> >>>> So I want to introduce a similar stub.c in arch/arm.
> >>>
> >>> While that's perhaps fine, ideally common bits would be common. Iirc
> >>> already back at the time I was wondering why stub.c had to be x86-
> >>> only.
> >>
> >> Some dummy functions in stub.c can be shared by arm or other
> architectures.
> >> But some functions like efi_multiboot2 are architecture dependent.
> >
> > Right - that's no different from the bulk of the non-stubbed EFI code.
> > I don't really mind you making an Arm-specific stub file if there's
> > not very much duplication, but it doesn't feel very good. In the end
> > it's up to the Arm maintainers anyway.
> 
> If the stubs are mostly the same then they should be common rather than
> duplicated.
> 
>  > x86/Makefile to gate these new macros, but it seems that we may need
>  > to change EFI build logic for x86. It will cause more risks for me.
> 
> But that would be a build risk right? If so, it is quite easy to
> verify/catch it compare to runtime issue.
> 
Risk may be not very accurate word. I mean, I was afraid that my changes
to x86 EFI build would introduce some unforeseen problems to x86. Because
I am not very familiar with that. As you and Jan think it's better, I will
try to do it.

> Cheers,
> 
> >
> > Jan
> >
> 
> --
> Julien Grall