linux-kernel - Re: [PATCH 1/3] drm/xe/kunit: fix link failure with built-in xe

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Message-Id: <79815966-a8fe-46cf-85ee-16657fa2392c@app.fastmail.com>
Date: Mon, 26 Feb 2024 13:46:01 +0100
From: "Arnd Bergmann" <arnd@...db.de>
To: "Lucas De Marchi" <lucas.demarchi@...el.com>,
 "Arnd Bergmann" <arnd@...nel.org>
Cc: "Oded Gabbay" <ogabbay@...nel.org>,
 Thomas Hellström <thomas.hellstrom@...ux.intel.com>,
 "Maarten Lankhorst" <maarten.lankhorst@...ux.intel.com>,
 "Maxime Ripard" <mripard@...nel.org>,
 "Thomas Zimmermann" <tzimmermann@...e.de>, "Dave Airlie" <airlied@...il.com>,
 "Daniel Vetter" <daniel@...ll.ch>, "Rodrigo Vivi" <rodrigo.vivi@...el.com>,
 "Matthew Brost" <matthew.brost@...el.com>,
 "Francois Dugast" <francois.dugast@...el.com>,
 "Jani Nikula" <jani.nikula@...el.com>,
 "Tejas Upadhyay" <tejas.upadhyay@...el.com>,
 "Matthew Auld" <matthew.auld@...el.com>,
 "Mauro Carvalho Chehab" <mchehab@...nel.org>,
 "Michal Wajdeczko" <michal.wajdeczko@...el.com>,
 "Matt Roper" <matthew.d.roper@...el.com>,
 "Daniele Ceraolo Spurio" <daniele.ceraolospurio@...el.com>,
 intel-xe@...ts.freedesktop.org, dri-devel@...ts.freedesktop.org,
 linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/3] drm/xe/kunit: fix link failure with built-in xe

On Mon, Feb 26, 2024, at 04:42, Lucas De Marchi wrote:
> On Sat, Feb 24, 2024 at 01:14:59PM +0100, Arnd Bergmann wrote:
>>From: Arnd Bergmann <arnd@...db.de>
>>
>>When the driver is built-in but the tests are in loadable modules,
>>the helpers don't actually get put into the driver:
>>
>>ERROR: modpost: "xe_kunit_helper_alloc_xe_device" [drivers/gpu/drm/xe/tests/xe_test.ko] undefined!
>>
>>Change the Makefile to ensure they are always part of the driver
>>even when the rest of the kunit tests are in loadable modules.
>>
>>The tests/xe_kunit_helpers.c file depends on DRM_KUNIT_TEST_HELPERS,
>>so this has to always be selected by the main XE module now, rather
>>than the actual tests. In turn, the "depends on (m || (y && KUNIT=y))"
>>doesn't really do what it tried and can just be removed.
>
> it actually did, which was to workaround issues prior to the commit you
> are pointing out.  What it did  was to make sure xe.ko is m, or if it's
> built-in, kunit is also built-in. Apparently the problem here is that
> the xe_test.ko is missing the symbols.

Ah, I misunderstood the intention, as I was thrown off by the
redundant 'y &&' which sounds like it was trying to force XE
to be built-in rather than modular when Kunit is !=m.

The more common way to write this is 'depends on KUNIT || !KUNIT',
with some drivers writing it as 'depends on m || KUNIT!=m'.

I double-checked now and found that the dependency is indeed
still needed:

WARNING: unmet direct dependencies detected for DRM_KUNIT_TEST_HELPERS
  Depends on [m]: HAS_IOMEM [=y] && DRM [=y] && KUNIT [=m]
  Selected by [y]:
  - DRM_XE [=y] && HAS_IOMEM [=y] && DRM [=y] && PCI [=y] && MMU [=y] && (ACPI_VIDEO [=y] || !ACPI [=y]) && DRM_XE_KUNIT_TEST [=m]!=n
  Selected by [m]:
  - DRM_KUNIT_TEST [=m] && HAS_IOMEM [=y] && DRM [=y] && KUNIT [=m] && MMU [=y]

> See commit 08987a8b6820 ("drm/xe: Fix build with KUNIT=m").
>
> I'm happy to remove it though if it's indeed not needed anymore.

Ideally the xe.ko module should not depend on anything exported
by lib/kunit, but for the moment, the tests/xe_kunit_helpers.o
file is still included in xe.ko and in turn depends on kunit.

Changing this is probably a little more complicated than my
patch, so I'll just send a v2 without the incorrect line.

     Arnd