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Subject: Re: [PATCH] mm/memtest: Add ARCH_USE_MEMTEST
To:     Anshuman Khandual <anshuman.khandual@arm.com>, linux-mm@kvack.org
Cc:     Chris Zankel <chris@zankel.net>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Michael Ellerman <mpe@ellerman.id.au>,
        linux-xtensa@linux-xtensa.org, linuxppc-dev@lists.ozlabs.org,
        linux-kernel@vger.kernel.org, Russell King <linux@armlinux.org.uk>,
        linux-mips@vger.kernel.org, Max Filippov <jcmvbkbc@gmail.com>,
        Ingo Molnar <mingo@redhat.com>,
        Paul Mackerras <paulus@samba.org>,
        Catalin Marinas <catalin.marinas@arm.com>,
        Thomas Gleixner <tglx@linutronix.de>,
        Will Deacon <will@kernel.org>,
        linux-arm-kernel@lists.infradead.org
References: <1612498242-31579-1-git-send-email-anshuman.khandual@arm.com>
From:   Vladimir Murzin <vladimir.murzin@arm.com>
Message-ID: <a58f1a92-087d-cf90-ce2b-0c88b39a8116@arm.com>
Date:   Fri, 5 Feb 2021 09:20:07 +0000
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Hi Anshuman,

On 2/5/21 4:10 AM, Anshuman Khandual wrote:
> early_memtest() does not get called from all architectures. Hence enabling
> CONFIG_MEMTEST and providing a valid memtest=[1..N] kernel command line
> option might not trigger the memory pattern tests as would be expected in
> normal circumstances. This situation is misleading.

Documentation already mentions which architectures support that:

memtest=        [KNL,X86,ARM,PPC] Enable memtest

yet I admit that not all reflected there

> 
> The change here prevents the above mentioned problem after introducing a
> new config option ARCH_USE_MEMTEST that should be subscribed on platforms
> that call early_memtest(), in order to enable the config CONFIG_MEMTEST.
> Conversely CONFIG_MEMTEST cannot be enabled on platforms where it would
> not be tested anyway.
> 

Is that generic pattern? What about other cross arch parameters? Do they already
use similar subscription or they rely on documentation?

I'm not against the patch just want to check if things are consistent...

Cheers
Vladimir