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From: =?UTF-8?q?Paul=20Heidekr=C3=BCger?= <paul.heidekrueger@tum.de>
To: Brendan Higgins <brendan.higgins@linux.dev>,
	David Gow <davidgow@google.com>,
	Mark Brown <broonie@kernel.org>,
	Shuah Khan <skhan@linuxfoundation.org>,
	=?UTF-8?q?Paul=20Heidekr=C3=BCger?= <paul.heidekrueger@tum.de>,
	linux-kselftest@vger.kernel.org (open list:KERNEL UNIT TESTING FRAMEWORK (KUnit)),
	kunit-dev@googlegroups.com (open list:KERNEL UNIT TESTING FRAMEWORK (KUnit)),
	linux-kernel@vger.kernel.org (open list)
Subject: [PATCH RFC] kunit: tool: add 'mte=on' qemu arg on arm64
Date: Wed, 14 Feb 2024 12:41:30 +0000
Message-Id: <20240214124131.990872-1-paul.heidekrueger@tum.de>
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Hi!

I was running some KASan tests with kunit.py recently and noticed that
when KASan is run in hw tags mode, we manually have to add the required
`mte=on` option to kunit_tool's qemu invocation, as the tests will
otherwise crash.

To make life easier, I was looking into ways for kunit.py to recognise
when MTE support was required and set the option automatically.

All solutions I could come up with for having kunit_tool conditionally
pass `mte=on` to qemu, either entailed duplicate code or required
parsing of kernel's config file again. I was working under the
assumption that only after configuring the kernel we would know whether
the 'mte=on' option was necessary, as CONFIG_ARM64_MTE is not visible
before.

Only afterwads did I realise that the qemu arm64 config that kunit_tool
falls back on, uses the `virt` machine, which supports MTE in any case.
So, could it be as easy as just adding the `mte=on` option to
kunit_tool's arm64 config? Would this be a welcome addition? 

What do you think? 

Many thanks,
Paul

Signed-off-by: Paul Heidekrüger <paul.heidekrueger@tum.de>
---
 tools/testing/kunit/qemu_configs/arm64.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/testing/kunit/qemu_configs/arm64.py b/tools/testing/kunit/qemu_configs/arm64.py
index d3ff27024755..a525f7e1093b 100644
--- a/tools/testing/kunit/qemu_configs/arm64.py
+++ b/tools/testing/kunit/qemu_configs/arm64.py
@@ -9,4 +9,4 @@ CONFIG_SERIAL_AMBA_PL011_CONSOLE=y''',
 			   qemu_arch='aarch64',
 			   kernel_path='arch/arm64/boot/Image.gz',
 			   kernel_command_line='console=ttyAMA0',
-			   extra_qemu_params=['-machine', 'virt', '-cpu', 'max,pauth-impdef=on'])
+			   extra_qemu_params=['-machine', 'virt,mte=on', '-cpu', 'max,pauth-impdef=on'])
-- 
2.40.1