[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

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

  • To: Stefano Stabellini <sstabellini@xxxxxxxxxx>, Wei Chen <Wei.Chen@xxxxxxx>
  • From: Jan Beulich <jbeulich@xxxxxxxx>
  • Date: Tue, 28 Sep 2021 10:02:45 +0200
  • Arc-authentication-results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=suse.com; dmarc=pass action=none header.from=suse.com; dkim=pass header.d=suse.com; arc=none
  • Arc-message-signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector9901; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version; bh=5yIna5NmEvZ/z/3EqYACdFIw5rgfUtwrjEFkAr2ZH1k=; b=XgW1KD/4t+2VcwieySn3g67ZbWsgYo34zXA9EbFKjZ+nLPb/mVZTeQR8NKGMeR1oKITCLWG3DtXCUwSjThyYrx2W8mSpM/NfR0w5OVN9OxZeprmEBh/2RUYjMisrQnVXsNb4iRT8Jg+JvowYpLdoQPyXZxU/4IBtcs6/W2ParHt6FomXZGo7MqS6qf4cpn5KUZzSQdnbORuwetj1DZ/Us/5eo2jXjaprUnkknusTCJNgBl+94tVnP7lGFscDvUidusTu9YViYp6IqgjkYFHGZjvMGBqyGGhbbFv3FcI7BiRYrglrUkFyejElHQGg0Hc0/+sZ5mUV7HXSNPAapV3eyg==
  • Arc-seal: i=1; a=rsa-sha256; s=arcselector9901; d=microsoft.com; cv=none; b=Co9mx8ssVjqdmgKHsRjroauvhQ7MsVInIRbVqQURlWpfy3Wjkma2EKPcPzqM3Y14HnZzaj/5yL+h3UlrP+BVVIIKd/ulXyoI3coQNsHkGdD3mJoC9/MSkM4nS9Hu90wPdtQyzI8pAiuY/fwI78qLMrXyO8PYasbZE7ANl4MkaTpwQ63zxk07wonYdam8/m2gGNjyfVhknSkKWv0KookoUvrw3ARfoh5c6zn4wL2EQ/W4odMugKgzK+cE+BnyGYiMYsMaIu1C3Iz9aO2vYCONgjh7WLSBYHdYY3Xru16QXGIBc4BFKk09TPZBHp4Xxvh2QgilI5gslwd7ZAUGqa+qdA==
  • Authentication-results: arm.com; dkim=none (message not signed) header.d=none;arm.com; dmarc=none action=none header.from=suse.com;
  • Cc: "xen-devel@xxxxxxxxxxxxxxxxxxxx" <xen-devel@xxxxxxxxxxxxxxxxxxxx>, "julien@xxxxxxx" <julien@xxxxxxx>, Bertrand Marquis <Bertrand.Marquis@xxxxxxx>
  • Delivery-date: Tue, 28 Sep 2021 08:02:59 +0000
  • List-id: Xen developer discussion <xen-devel.lists.xenproject.org>

On 28.09.2021 07:01, Stefano Stabellini wrote:
> On Tue, 28 Sep 2021, Wei Chen wrote:
>>> -----Original Message-----
>>> From: Stefano Stabellini <sstabellini@xxxxxxxxxx>
>>> Sent: 2021年9月28日 9:00
>>> To: Wei Chen <Wei.Chen@xxxxxxx>
>>> Cc: Jan Beulich <jbeulich@xxxxxxxx>; 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 Mon, 27 Sep 2021, Wei Chen wrote:
>>>>> -----Original Message-----
>>>>> From: Xen-devel <xen-devel-bounces@xxxxxxxxxxxxxxxxxxxx> On Behalf Of
>>> Wei
>>>>> Chen
>>>>> Sent: 2021年9月26日 18:25
>>>>> To: Jan Beulich <jbeulich@xxxxxxxx>
>>>>> 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
>>>>> 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
>>>> 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
> I am OK with that. Another option is to rename XEN_BUILD_EFI to
> CONFIG_XEN_BUILD_EFI on x86. Either way is fine by me. Jan, do you havea
> preference?

Yes, I do: No new CONFIG_* settings please that don't originate from
Kconfig. Hence I'm afraid this is a "no" to your suggestion.

Mid-term we should try to get rid of the remaining CONFIG_* which
get #define-d in e.g. asm/config.h.




Lists.xenproject.org is hosted with RackSpace, monitoring our
servers 24x7x365 and backed by RackSpace's Fanatical Support®.