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From:   Michael Ellerman <mpe@ellerman.id.au>
To:     Eric DeVolder <eric.devolder@oracle.com>,
        Kees Cook <keescook@chromium.org>
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Subject: Re: [PATCH v1 00/21] refactor Kconfig to consolidate KEXEC and
 CRASH options
In-Reply-To: <8a97f096-2bdc-0298-a1c5-8d48dbf94179@oracle.com>
References: <20230612172805.681179-1-eric.devolder@oracle.com>
 <202306131314.EFA558B7@keescook>
 <8a97f096-2bdc-0298-a1c5-8d48dbf94179@oracle.com>
Date:   Thu, 15 Jun 2023 13:26:35 +1000
Message-ID: <87ilbpflsk.fsf@mail.lhotse>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Eric DeVolder <eric.devolder@oracle.com> writes:
> On 6/13/23 15:21, Kees Cook wrote:
>> On Mon, Jun 12, 2023 at 01:27:52PM -0400, Eric DeVolder wrote:
>>> The Kconfig is refactored to consolidate KEXEC and CRASH options from
>>> various arch/<arch>/Kconfig files into new file kernel/Kconfig.kexec.
>> 
>> This looks very nice!
>> 
> Thank you Kees!
>
>>> [...]
>>> - The boolean ARCH_HAS_<option> in effect allows the arch to determine
>>>    when the feature is allowed.  Archs which don't have the feature
>>>    simply do not provide the corresponding ARCH_HAS_<option>.
>>>    For each arch, where there previously were KEXEC and/or CRASH
>>>    options, these have been replaced with the corresponding boolean
>>>    ARCH_HAS_<option>, and an appropriate def_bool statement.
>>>
>>>    For example, if the arch supports KEXEC_FILE, then the
>>>    ARCH_HAS_KEXEC_FILE simply has a 'def_bool y'. This permits the
>>>    KEXEC_FILE option to be available.
>>>
>>>    If the arch has a 'depends on' statement in its original coding
>>>    of the option, then that expression becomes part of the def_bool
>>>    expression. For example, arm64 had:
>>>
>>>    config KEXEC
>>>      depends on PM_SLEEP_SMP
>>>
>>>    and in this solution, this converts to:
>>>
>>>    config ARCH_HAS_KEXEC
>>>      def_bool PM_SLEEP_SMP
>>>
>>>
>>> - In order to account for the differences in the config coding for
>>>    the three common options, the ARCH_SUPPORTS_<option> is used.
>>>    This options has a 'depends on <option>' statement to couple it
>>>    to the main option, and from there can insert the differences
>>>    from the common option and the arch original coding of that option.
>>>
>>>    For example, a few archs enable CRYPTO and CRYTPO_SHA256 for
>>>    KEXEC_FILE. These require a ARCH_SUPPORTS_KEXEC_FILE and
>>>    'select CRYPTO' and 'select CRYPTO_SHA256' statements.
>> 
>> Naming nit: "HAS" and "SUPPORTS" feel very similar, and looking at
>> existing configs, "ARCH_SUPPORTS_..." is already used for doing this
>> kind of bare "bool" management. e.g. see ARCH_SUPPORTS_INT128
>> 
>> It looks like you need to split "depends" and "select" so the options
>> can be chosen separately from the "selectable" configs.
>> 
>> How about naming this ARCH_SELECTS_<option>, since that's what it's
>> there for?
>> 
> I'm OK with this. Let's see if others agree?

Yeah please rename one or both of them. At a glance the difference
between HAS and SUPPORTS is very non-obvious.

I like Kees' suggestion to use ARCH_SUPPORTS and ARCH_SELECTS.

cheers