Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Message-ID: <91873ac5-a15d-a405-c2ee-24674e17cbd3@amd.com>
Date:   Wed, 29 Mar 2023 09:04:55 +0200
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101
 Thunderbird/102.8.0
Subject: Re: [PATCH 1/2] drm: buddy_allocator: Fix buddy allocator init on
 32-bit systems
Content-Language: en-US
To:     David Gow <davidgow@google.com>,
        =?UTF-8?Q?Lu=c3=ads_Mendes?= <luis.p.mendes@gmail.com>,
        Maarten Lankhorst <maarten.lankhorst@linux.intel.com>,
        Maxime Ripard <mripard@kernel.org>,
        Thomas Zimmermann <tzimmermann@suse.de>,
        David Airlie <airlied@gmail.com>,
        Daniel Vetter <daniel@ffwll.ch>,
        =?UTF-8?Q?Ma=c3=adra_Canal?= <mairacanal@riseup.net>,
        Arthur Grillo <arthurgrillo@riseup.net>
Cc:     dri-devel@lists.freedesktop.org, linux-kernel@vger.kernel.org
References: <20230329065532.2122295-1-davidgow@google.com>
From:   =?UTF-8?Q?Christian_K=c3=b6nig?= <christian.koenig@amd.com>
In-Reply-To: <20230329065532.2122295-1-davidgow@google.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
MIME-Version: 1.0
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?SWFYUy9qMlNDajJOWjlvZmxOS0NKNWZaZ1QrZmw0azcyREZNeVNORWNIazlN?=
 =?utf-8?B?NkJkRUFpWUR4RVJ4MThxQnF0UEY5R1RGSEZtV0FjT0JOQmhlRG5ReEM3TDRZ?=
 =?utf-8?B?N2FzWjJyc3lSMzdwNEpoQkVzY095QjFqUlEyZkg1K1lUcTJiNU5RZDVXbEY4?=
 =?utf-8?B?MjBzdi81ZFdDa2JHVHcrbDRvdE1HU0JTS3NQR0haT0w2OXFiRmVabysrQU8v?=
 =?utf-8?B?eERuTnlVZ0k3ajRuNzFsUkhHK3hCbU1ZcS8wTUZWZ1RUWmxBMVdWTmJJSms1?=
 =?utf-8?B?WWlZRGpubks5cHBUN3VCc1VTSkdOS3hNbEhZdnhkSzhKYjRYN3hwNzgvbTFo?=
 =?utf-8?B?ajdhZVpLNGYvWUU0czU2NjI0YnZKa3B4RmFtK0pCWnZDWUxneUNDTXM0dW5v?=
 =?utf-8?B?TnhrS0FOOU1LamU5WVhNNmp6T2prTEM1SExpbU1BM1NqNEFoMGVPN2YvSEp4?=
 =?utf-8?B?ZTZicVJDOE5JdGk5N08yZDZCeFp1R0p1OWlsMXBUMGZUTFF2QWx6RkNPd2lN?=
 =?utf-8?B?dVM3TmRuQkNCQ2VSNkhFK0I5V3VibmZvR2o1cWlsc0ZQdXdPR3huVG1EQVh1?=
 =?utf-8?B?WGRYMnA4MUlTU3YyMmticmkvZWlTbEFJSXlhWHZNc0RFTHhYTGVIRDVpMDRX?=
 =?utf-8?B?dW1QM21Yc2p2QzZibWNtcFNOOG5jZm5HRlFKWGd2WGRPNlF3YUpuaWRLcXN3?=
 =?utf-8?B?a0ZGS0V5dG4wMCtRcnNmTDZuRllXR215Z0l2TUE4TVpEdEdiZk9XbTJtMitz?=
 =?utf-8?B?UjBKbkZhdjNpOHZiWFdHL3FUZUhXR1pmQVRuRXZiSmgzdzFhcU9lYlZocUEz?=
 =?utf-8?B?c3h3c3M4Zi9NL0lMTUxITXpZWnpDWkxJUDdTOFFMUjN3V3diZ2Rpc1ROMDVV?=
 =?utf-8?B?Y2VnTlBJcG9PbndWMHhBaUlYV2NpalpFMGZ4SFJBWUdiVGFOTlpQaU5lK1NS?=
 =?utf-8?B?L3hsaVNCWnZEdWxndWFsVmt4bXo2WEtxVnl6enhFcDl4UWJNN1lUdlhYaTBk?=
 =?utf-8?B?YzQ3ZHFDcVNYaHMra3NYTmxUVWlBR2RCOWFiQkc5OUw4UzJZdlhXMitzTlpU?=
 =?utf-8?B?RXhpemtNbFN0ZXp4b2Z3K1krLzRDbG9lVlNVVzRzYkt5djRiMEd2R1BRVnNQ?=
 =?utf-8?B?bitRenpyQ3lhaDFDZnk0c2VlYUxnbzRXcnZxS0cwc2pGZEwycVkxSVlYRk1t?=
 =?utf-8?B?NGZaNlZOeWNUZEN3VWhCckJac1pidUNmQ2p3aEVIRkxjVmNCTGlPbE51TVEr?=
 =?utf-8?B?VEx1R01oTU83Z1RiVjFSa0xhRW0rcEN2eTBOeXo3QVU3TGdsRVN5cElrTnNW?=
 =?utf-8?B?Y09xOTZzY0lqM0ljbTAzVXVWRm8vZk5PSXRPTVRkT2J4TGVtSE5wbEtUU254?=
 =?utf-8?B?a1JCcmFjRWZDcGc0cWpXRCtHNEtoY1hPaXVzSWRmdUhnU0V6QUZBTlVjTnRB?=
 =?utf-8?B?Yk9vcDFydFNkbFFIaGdMbU9XdlZNTW0zaElVeHRCWUdnK0Q5RDVyTjJhNzRX?=
 =?utf-8?B?ekZnbWxqWEt0UEQxRWYyYW90NmFuQWZTWWlFUVMwdjNRdkViWU9nT1JnV3BU?=
 =?utf-8?B?Z2lWWkl0N1FsZkYya0JMbWwwaGFrTFVHTTB1OER4VFV0azJXd1FYaUtiY0Vm?=
 =?utf-8?B?elFVVlduY1JXcU80WXpBYVdrVjlLaTRlYnpiak51WlV0Z3NSZ1Z5K1FXeGFq?=
 =?utf-8?B?RUxRTzFUY2lmWTluWVIxQkk3Nk9iczRVaS90V3FSVkYzd3RzTHVpZU9EdXFs?=
 =?utf-8?B?S2p2TjJQbS9icXJxN0FzUVVTcm1ZWHpWR3d2QkpHYzc3bWozcDdPMWRpdHNn?=
 =?utf-8?B?djZvaXNla3FZVHB4RENYc1EySkttOENHa2dMRFZLSzZrdTdJWnI0ZEYzNnJM?=
 =?utf-8?B?cWorY2lwNm1LYThUMFI0ZDhrUWNQRUx0MnI3eSthZkU5bzRxeU01T1FzZk1u?=
 =?utf-8?B?bW5lWXJPbzM2VVJROWZZaUt0TUp3YmltOVN0SmtHNGZrU0dTUjAyVEllejhv?=
 =?utf-8?B?aXlzeHd1VU9wcHVtSFFpZU5hSFpuVTJiYXEvdDVmUWRCK3VHQjhsdUtPWU9i?=
 =?utf-8?B?Nll4Qy8wbXREbkxRczNwanFmQVdOdUVYeEpFTHJBb2hlMzk3OEVlM3Y4dmFx?=
 =?utf-8?B?a0dPc1prbEhwa2xHQWQraGlEZmd3Y21rUUw4VTV6Tk5aZSt3Z3ExWFdXZTlZ?=
 =?utf-8?Q?Ayh7rhnhVf6yWHkoHh+f2SVzRbajjfwNe825klzwcsq0?=
X-OriginatorOrg: amd.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 4dc424d6-0c79-4098-4f4c-08db3023e995
X-MS-Exchange-CrossTenant-AuthSource: BN8PR12MB3587.namprd12.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 29 Mar 2023 07:05:00.6023
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: HQsJHHfZjcQjbqEDj9dKrd9cW5ZXqdhpiMwl6lVtVqbbkzVERl8HPzGT76XmdHiK
X-MS-Exchange-Transport-CrossTenantHeadersStamped: CH3PR12MB8753
X-Spam-Status: No, score=-0.2 required=5.0 tests=DKIM_SIGNED,DKIM_VALID,
        DKIM_VALID_AU,DKIM_VALID_EF,FORGED_SPF_HELO,NICE_REPLY_A,
        RCVD_IN_DNSWL_NONE,RCVD_IN_MSPIKE_H2,SPF_HELO_PASS,SPF_NONE
        autolearn=unavailable autolearn_force=no version=3.4.6
X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on
        lindbergh.monkeyblade.net
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

Am 29.03.23 um 08:55 schrieb David Gow:
> The drm buddy allocator tests were broken on 32-bit systems, as
> rounddown_pow_of_two() takes a long, and the buddy allocator handles
> 64-bit sizes even on 32-bit systems.
>
> This can be reproduced with the drm_buddy_allocator KUnit tests on i386:
> 	./tools/testing/kunit/kunit.py run --arch i386 \
> 	--kunitconfig ./drivers/gpu/drm/tests drm_buddy
>
> (It results in kernel BUG_ON() when too many blocks are created, due to
> the block size being too small.)
>
> This was independently uncovered (and fixed) by Luís Mendes, whose patch
> added a new u64 variant of rounddown_pow_of_two(). This version instead
> recalculates the size based on the order.
>
> Reported-by: Luís Mendes <luis.p.mendes@gmail.com>
> Link: https://lore.kernel.org/lkml/CAEzXK1oghXAB_KpKpm=-CviDQbNaH0qfgYTSSjZgvvyj4U78AA@mail.gmail.com/T/
> Signed-off-by: David Gow <davidgow@google.com>

Acked-by: Christian König <christian.koenig@amd.com> for the series.

> ---
>   drivers/gpu/drm/drm_buddy.c | 4 ++--
>   1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/gpu/drm/drm_buddy.c b/drivers/gpu/drm/drm_buddy.c
> index 3d1f50f481cf..7098f125b54a 100644
> --- a/drivers/gpu/drm/drm_buddy.c
> +++ b/drivers/gpu/drm/drm_buddy.c
> @@ -146,8 +146,8 @@ int drm_buddy_init(struct drm_buddy *mm, u64 size, u64 chunk_size)
>   		unsigned int order;
>   		u64 root_size;
>   
> -		root_size = rounddown_pow_of_two(size);
> -		order = ilog2(root_size) - ilog2(chunk_size);
> +		order = ilog2(size) - ilog2(chunk_size);
> +		root_size = chunk_size << order;
>   
>   		root = drm_block_alloc(mm, NULL, order, offset);
>   		if (!root)