On Mon, Mar 01, 2021 at 10:02:06AM +0530, 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.

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.

Cc: Russell King <linux@armlinux.org.uk>
Cc: Catalin Marinas <catalin.marinas@arm.com>
Cc: Will Deacon <will@kernel.org>
Cc: Thomas Bogendoerfer <tsbogend@alpha.franken.de>
Cc: Michael Ellerman <mpe@ellerman.id.au>
Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org>
Cc: Paul Mackerras <redacted>
Cc: Thomas Gleixner <redacted>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Chris Zankel <chris@zankel.net>
Cc: Max Filippov <jcmvbkbc@gmail.com>
Cc: linux-arm-kernel@lists.infradead.org
Cc: linux-mips@vger.kernel.org
Cc: linuxppc-dev@lists.ozlabs.org
Cc: linux-xtensa@linux-xtensa.org
Cc: linux-mm@kvack.org
Cc: linux-kernel@vger.kernel.org
Reviewed-by: Max Filippov <jcmvbkbc@gmail.com>
Signed-off-by: Anshuman Khandual <redacted>

For arm64:

Acked-by: Catalin Marinas <catalin.marinas@arm.com>