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

From: Jan Beulich <jbeulich@suse.com>
To: Wei Chen <Wei.Chen@arm.com>
Cc: Bertrand Marquis <Bertrand.Marquis@arm.com>,
	"xen-devel@lists.xenproject.org" <xen-devel@lists.xenproject.org>,
	"sstabellini@kernel.org" <sstabellini@kernel.org>,
	"julien@xen.org" <julien@xen.org>
Subject: Re: [PATCH 20/37] xen: introduce CONFIG_EFI to stub API for non-EFI architecture
Date: Thu, 27 Jan 2022 10:00:20 +0100	[thread overview]
Message-ID: <e135adab-8b21-8dc0-2518-e505a59feb9f@suse.com> (raw)
In-Reply-To: <PAXPR08MB7420252BFA15D032BDDF2F4A9E219@PAXPR08MB7420.eurprd08.prod.outlook.com>

On 27.01.2022 09:51, Wei Chen wrote:
>> From: Xen-devel <xen-devel-bounces@lists.xenproject.org> On Behalf Of Wei
>> Chen
>> Sent: 2022年1月27日 16:45
>>
>>> From: Jan Beulich <jbeulich@suse.com>
>>> Sent: 2022年1月25日 18:35
>>>
>>> On 23.09.2021 14:02, Wei Chen wrote:
>>>> --- a/xen/common/Kconfig
>>>> +++ b/xen/common/Kconfig
>>>> @@ -11,6 +11,16 @@ config COMPAT
>>>>  config CORE_PARKING
>>>>  	bool
>>>>
>>>> +config EFI
>>>> +	bool
>>>> +	---help---
>>>> +      This option provides support for runtime services provided
>>>> +      by UEFI firmware (such as non-volatile variables, realtime
>>>> +      clock, and platform reset). A UEFI stub is also provided to
>>>> +      allow the kernel to be booted as an EFI application. This
>>>> +      is only useful for kernels that may run on systems that have
>>>> +      UEFI firmware.
>>>
>>> The way enabling of (full) EFI support works on x86, I consider it
>>> wrong / misleading to put the option in common code. At the very least
>>> the help text would need to call out the extra dependencies. Plus the
>>> help text of course then needs to be generic (i.e. applicable to both
>>> Arm and x86). That's notwithstanding the fact that without a prompt
>>> the help text won't ever be seen while configuring Xen.
>>>
>>> Also (nit): Indentation. And please don't use ---help--- anymore in
>>> new code.
>>>
>>
>> I have used CONFIG_ARM_EFI to replace this common EFI config in my
>> latest version. This Kconfig option has been removed.
>> And thanks, I will not use --help-- anymore.
>>
>>>> --- a/xen/include/xen/efi.h
>>>> +++ b/xen/include/xen/efi.h
>>>> @@ -25,6 +25,8 @@ extern struct efi efi;
>>>>
>>>>  #ifndef __ASSEMBLY__
>>>>
>>>> +#ifdef CONFIG_EFI
>>>> +
>>>>  union xenpf_efi_info;
>>>>  union compat_pf_efi_info;
>>>>
>>>> @@ -45,6 +47,8 @@ int efi_runtime_call(struct xenpf_efi_runtime_call
>> *);
>>>>  int efi_compat_get_info(uint32_t idx, union compat_pf_efi_info *);
>>>>  int efi_compat_runtime_call(struct compat_pf_efi_runtime_call *);
>>>>
>>>> +#endif /* CONFIG_EFI*/
>>>
>>> I can see that in the later patch, when introducing inline stubs,
>>> you would need conditionals here, but I don't think you need them
>>> right here (or you may want to introduce the stubs right away).
>>>
>>> Also (nit): Missing blank in the comment.
> 
> I am sorry, I had missed this comment. In my latest changes,
> I have introduced a stub file for non-EFI architectures.
> The reason why we don't use a macro to stub the helpers
> in efi.h is that, some architectures have implemented stub
> helpers in their stub.c. If we define stub helpers in
> efi.h, this will cause function redefinition error. We need
> to fix this error for all architectures. And some helpers
> is not easy to implement as a inline function in efi.h.
> So we use stub file instead of stubing in efi.h

But you realize we already have such a stub file on x86?

Jan