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

[Wei Chen <Wei.Chen@xxxxxxx>]

Hi Jan,

> -----Original Message-----
> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of Jan
> Beulich
> Sent: 2021年9月24日 18:49
> To: Wei Chen <Wei.Chen@xxxxxxx>
> Cc: xen-devel@xxxxxxxxxxxxxxxxxxxx; julien@xxxxxxx; Bertrand Marquis
> <Bertrand.Marquis@xxxxxxx>; Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Subject: Re: [PATCH 20/37] xen: introduce CONFIG_EFI to stub API for non-
> EFI architecture
> 
> On 24.09.2021 12:31, Wei Chen wrote:
> >> From: Jan Beulich <jbeulich@xxxxxxxx>
> >> Sent: 2021年9月24日 15:59
> >>
> >> On 24.09.2021 06:34, Wei Chen wrote:
> >>>> From: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> >>>> Sent: 2021年9月24日 9:15
> >>>>
> >>>> On Thu, 23 Sep 2021, Wei Chen wrote:
> >>>>> --- a/xen/common/Kconfig
> >>>>> +++ b/xen/common/Kconfig
> >>>>> @@ -11,6 +11,16 @@ config COMPAT
> >>>>>  config CORE_PARKING
> >>>>>         bool
> >>>>>
> >>>>> +config EFI
> >>>>> +       bool
> >>>>
> >>>> Without the title the option is not user-selectable (or de-
> selectable).
> >>>> So the help message below can never be seen.
> >>>>
> >>>> Either add a title, e.g.:
> >>>>
> >>>> bool "EFI support"
> >>>>
> >>>> Or fully make the option a silent option by removing the help text.
> >>>
> >>> OK, in current Xen code, EFI is unconditionally compiled. Before
> >>> we change related code, I prefer to remove the help text.
> >>
> >> But that's not true: At least on x86 EFI gets compiled depending on
> >> tool chain capabilities. Ultimately we may indeed want a user
> >> selectable option here, but until then I'm afraid having this option
> >> at all may be misleading on x86.
> >>
> >
> > I check the build scripts, yes, you're right. For x86, EFI is not a
> > selectable option in Kconfig. I agree with you, we can't use Kconfig
> > system to decide to enable EFI build for x86 or not.
> >
> > So how about we just use this EFI option for Arm only? Because on Arm,
> > we do not have such toolchain dependency.
> 
> To be honest - don't know. That's because I don't know what you want
> to use the option for subsequently.
> 

In last version, I had introduced an arch-helper to stub EFI_BOOT
in Arm's common code for Arm32. Because Arm32 doesn't support EFI.
So Julien suggested me to introduce a CONFIG_EFI option for non-EFI
supported architectures to stub in EFI layer.

[1] https://lists.xenproject.org/archives/html/xen-devel/2021-08/msg00808.html

> Jan
>