Re: [PATCH RESEND 2/2] xen: Allow EXPERT mode to be selected from the menuconfig directly

From: Jan Beulich <jbeulich@suse.com>
To: Julien Grall <julien@xen.org>
Cc: Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
	Andrew Cooper <andrew.cooper3@citrix.com>,
	Julien Grall <jgrall@amazon.com>,
	Ian Jackson <ian.jackson@eu.citrix.com>,
	George Dunlap <george.dunlap@citrix.com>,
	xen-devel@lists.xenproject.org
Subject: Re: [PATCH RESEND 2/2] xen: Allow EXPERT mode to be selected from the menuconfig directly
Date: Mon, 4 May 2020 12:18:43 +0200	[thread overview]
Message-ID: <cb829776-b18d-3535-1869-da9dc2232ec8@suse.com> (raw)
In-Reply-To: <3c581eac-9b2f-493c-f86e-2377450a6a2a@xen.org>

On 04.05.2020 11:54, Julien Grall wrote:
> Hi Jan,
> 
> On 04/05/2020 10:37, Jan Beulich wrote:
>> On 04.05.2020 11:30, Julien Grall wrote:
>>> Hi Jan,
>>>
>>> On 04/05/2020 10:18, Jan Beulich wrote:
>>>> On 30.04.2020 17:35, Julien Grall wrote:
>>>>> On 30/04/2020 15:50, Jan Beulich wrote:
>>>>>> On 30.04.2020 16:25, Julien Grall wrote:
>>>>>>> EXPERT mode is currently used to gate any options that are in technical
>>>>>>> preview or not security supported At the moment, the only way to select
>>>>>>> it is to use XEN_CONFIG_EXPERT=y on the make command line.
>>>>>>>
>>>>>>> However, if the user forget to add the option of one of the make
>>>>>>> command (even a clean), then .config will get rewritten. This may lead
>>>>>>> to a rather frustrating experience as it is difficult to diagnostic the
>>>>>>> issue.
>>>>>>
>>>>>> Is / will this still be true after Anthony's rework of the build
>>>>>> system? Right now we already have
>>>>>>
>>>>>> clean-targets := %clean
>>>>>> no-dot-config-targets := $(clean-targets) \
>>>>>>                             ...
>>>>>
>>>>> I haven't tried Anthony's rework yet. But I guess the problem would
>>>>> be the same if you forget to add XEN_CONFIG_EXPERT=y on make.
>>>>
>>>> Why? xen/.config would get re-written only if kconfig got run in
>>>> the first place. It is my understanding that no-dot-config-targets
>>>> exist to avoid including .config, and as a result make won't find
>>>> a need anymore to cause it to re-made if out of date.
>>>
>>> kconfig may be executed because you change one of the */Kconfig file.
>>> So if you happen to forget XEN_CONFIG_EXPERT=y on your build command
>>> line, then you will have your .config rewritten without expert options.
>>
>> That's still a build system issue then (if this is really what happens):
>> Dependencies of xen/.config shouldn't be evaluated as long as it doesn't
>> get used.
> 
> I am not sure to understand what you mean by "doesn't get used here". When you build Xen, xen/.config is a dependency for the auto-generated header. So 'make' will actually check whether there are any modification in */Kconfig.

But you were talking about "make clean", weren't you?

Jan