linux-kernel - Re: [PATCH 0/4] ARM: Support KFENCE feature

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Date:   Wed, 25 Aug 2021 22:15:39 +0800
From:   Kefeng Wang <wangkefeng.wang@...wei.com>
To:     Marco Elver <elver@...gle.com>
CC:     Russell King <linux@...linux.org.uk>,
        Alexander Potapenko <glider@...gle.com>,
        Dmitry Vyukov <dvyukov@...gle.com>,
        <linux-arm-kernel@...ts.infradead.org>,
        <linux-kernel@...r.kernel.org>, <kasan-dev@...glegroups.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH 0/4] ARM: Support KFENCE feature


On 2021/8/25 18:57, Marco Elver wrote:
> On Wed, Aug 25, 2021 at 12:14PM +0200, Marco Elver wrote:
>> On Wed, 25 Aug 2021 at 11:17, Kefeng Wang <wangkefeng.wang@...wei.com> wrote:
>>> The patch 1~3 is to support KFENCE feature on ARM.
>>>
>>> NOTE:
>>> The context of patch2/3 changes in arch/arm/mm/fault.c is based on link[1],
>>> which make some refactor and cleanup about page fault.
>>>
>>> kfence_test is not useful when kfence is not enabled, skip kfence test
>>> when kfence not enabled in patch4.
>>>
>>> I tested the kfence_test on ARM QEMU with or without ARM_LPAE and all passed.
>> Thank you for enabling KFENCE on ARM -- I'll leave arch-code review to
>> an ARM maintainer.
>>
>> However, as said on the patch, please drop the change to the
>> kfence_test and associated changes. This is working as intended; while
>> you claim that it takes a long time to run when disabled, when running
>> manually you just should not run it when disabled. There are CI
>> systems that rely on the KUnit test output and the fact that the
>> various test cases say "not ok" etc. Changing that would mean such CI
>> systems would no longer fail if KFENCE was accidentally disabled (once
>> KFENCE is enabled on various CI, which we'd like to do at some point).
>> There are ways to fail the test faster, but they all complicate the
>> test for no good reason. (And the addition of a new exported function
>> that is essentially useless.)
> I spoke too soon -- we export __kfence_pool, and that's good enough to
> fail the test fast if KFENCE was disabled at boot:
>
> 	https://lkml.kernel.org/r/20210825105533.1247922-1-elver@google.com
>
> will do the trick. So please drop your patch 4/4 here.
Sure , please ignore it.
>
> Thanks,
> -- Marco
> .
>