Hi Stefano, > -----Original Message----- > From: Stefano Stabellini <sstabell...@kernel.org> > Sent: 2021年9月28日 9:00 > To: Wei Chen <wei.c...@arm.com> > Cc: Jan Beulich <jbeul...@suse.com>; xen-devel@lists.xenproject.org; > jul...@xen.org; Bertrand Marquis <bertrand.marq...@arm.com>; Stefano > Stabellini <sstabell...@kernel.org> > Subject: RE: [PATCH 20/37] xen: introduce CONFIG_EFI to stub API for non- > EFI architecture > > On Mon, 27 Sep 2021, Wei Chen wrote: > > > -----Original Message----- > > > From: Xen-devel <xen-devel-boun...@lists.xenproject.org> On Behalf Of > Wei > > > Chen > > > Sent: 2021年9月26日 18:25 > > > To: Jan Beulich <jbeul...@suse.com> > > > Cc: xen-devel@lists.xenproject.org; jul...@xen.org; Bertrand Marquis > > > <bertrand.marq...@arm.com>; Stefano Stabellini <sstabell...@kernel.org> > > > Subject: RE: [PATCH 20/37] xen: introduce CONFIG_EFI to stub API for > non- > > > EFI architecture > > > > > > Hi Jan, > > > > > > > -----Original Message----- > > > > From: Xen-devel <xen-devel-boun...@lists.xenproject.org> On Behalf > Of > > > Jan > > > > Beulich > > > > Sent: 2021年9月24日 18:49 > > > > To: Wei Chen <wei.c...@arm.com> > > > > Cc: xen-devel@lists.xenproject.org; jul...@xen.org; Bertrand Marquis > > > > <bertrand.marq...@arm.com>; Stefano Stabellini > <sstabell...@kernel.org> > > > > 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 <jbeul...@suse.com> > > > > >> Sent: 2021年9月24日 15:59 > > > > >> > > > > >> On 24.09.2021 06:34, Wei Chen wrote: > > > > >>>> From: Stefano Stabellini <sstabell...@kernel.org> > > > > >>>> 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 > > > > > > > As Jan' reminded, x86 doesn't depend on Kconfig to build EFI code. > > So, if we CONFIG_EFI to stub EFI API's for x86, we will encounter > > that toolchains enable EFI, but Kconfig disable EFI. Or Kconfig > > enable EFI but toolchain doesn't provide EFI build supports. And > > then x86 could not work well. > > > > If we use CONFIG_EFI for Arm only, that means CONFIG_EFI for x86 > > is off, this will also cause problem. > > > > So, can we still use previous arch_helpers to stub for Arm32? > > until x86 can use this selectable option? > > EFI doesn't have to be necessarily a user-visible option in Kconfig at > this point. I think Julien was just asking to make the #ifdef based on > a EFI-related config rather than just based CONFIG_ARM64. > > On x86 EFI is detected based on compiler support, setting XEN_BUILD_EFI > in xen/arch/x86/Makefile. Let's say that we keep using the same name > "XEN_BUILD_EFI" on ARM as well. > > On ARM32, XEN_BUILD_EFI should be always unset. > > On ARM64 XEN_BUILD_EFI should be always set. > > That's it, right? I'd argue that CONFIG_EFI or HAS_EFI are better names > than XEN_BUILD_EFI, but that's OK anyway. So for instance you can make > XEN_BUILD_EFI an invisible symbol in xen/arch/arm/Kconfig and select it > only on ARM64.
Thanks, this is a good approach. But if we place XEN_BUILD_EFI in Kconfig it will be transfer to CONFIG_XEN_BUILD_EFI. How about using another name in Kconfig like ARM_EFI, but use CONFIG_ARM_EFI in config.h to define XEN_BUILD_EFI?
