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Date: Mon, 19 Feb 2024 12:29:57 +0100
From: "Arnd Bergmann" <arnd@arndb.de>
To: =?UTF-8?Q?Christian_K=C3=B6nig?= <christian.koenig@amd.com>,
 "Randy Dunlap" <rdunlap@infradead.org>, "Arnd Bergmann" <arnd@kernel.org>,
 "Maarten Lankhorst" <maarten.lankhorst@linux.intel.com>,
 "Maxime Ripard" <mripard@kernel.org>,
 "Thomas Zimmermann" <tzimmermann@suse.de>
Cc: "Dave Airlie" <airlied@gmail.com>, "Daniel Vetter" <daniel@ffwll.ch>,
 "Arunpravin Paneer Selvam" <Arunpravin.PaneerSelvam@amd.com>,
 "David Gow" <davidgow@google.com>,
 =?UTF-8?Q?Ma=C3=ADra_Canal?= <mcanal@igalia.com>,
 "Matthew Auld" <matthew.auld@intel.com>, dri-devel@lists.freedesktop.org,
 linux-kernel@vger.kernel.org
Subject: Re: [PATCH] drm/tests/drm_buddy: avoid 64-bit calculation
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On Mon, Feb 19, 2024, at 12:22, Christian K=C3=B6nig wrote:
> Am 17.02.24 um 02:31 schrieb Randy Dunlap:
>> On 2/16/24 12:24, Arnd Bergmann wrote:
>>> From: Arnd Bergmann <arnd@arndb.de>
>>>
>>> The newly added drm_test_buddy_alloc_contiguous() test fails to link=
 on
>>> 32-bit targets because of inadvertent 64-bit calculations:
>>>
>>> ERROR: modpost: "__aeabi_uldivmod" [drivers/gpu/drm/tests/drm_buddy_=
test.ko] undefined!
>>> ERROR: modpost: "__aeabi_ldivmod" [drivers/gpu/drm/tests/drm_buddy_t=
est.ko] undefined!
>>>
>>> >From what I can tell, the numbers cannot possibly overflow a 32-bit=
 size,
>>> so use different types for these.
>>>
>>> I noticed that the function has another possible flaw in that is mix=
es
>>> what it calls pages with 4KB units. This is a big confusing at best,
>>> or possibly broken when built on machines with larger pages.
>>>
>>> Fixes: a64056bb5a32 ("drm/tests/drm_buddy: add alloc_contiguous test=
")
>>> Signed-off-by: Arnd Bergmann <arnd@arndb.de>
>> Tested-by: Randy Dunlap <rdunlap@infradead.org>
>
> I've just pushed a similar patch Mathew came up a bit earlier to=20
> drm-misc-fixes.
>
> Sorry for the noise, I have to catch up on picking up patches for=20
> misc-fixes and misc-next.

Ok, thanks.

Have you looked at how this code works for larger values of PAGE_SIZE?
Is there any need to change other things or will this work with the
hardcoded 4KB chunks?

     Arnd