From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from BN8PR05CU002.outbound.protection.outlook.com (mail-eastus2azon11011033.outbound.protection.outlook.com [52.101.57.33]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id F3144455635; Wed, 23 Sep 2026 08:03:36 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=52.101.57.33 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790150618; cv=fail; b=QdP90L/QWxugEnuzsmk5VnKajXrgvCtfVu45I0trCTi9b+ufJZ87a5+iaRbg0nrf+jYf90m5H1vqswVvAh103YyJsIXHe1ohJyaZsCp7xniM4qbXQtEHukZTWlAd7wqpmMoWLCDOD0moocPcxpvSDw1xHMsMRmC/J5oCFCzBLQk= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1790150618; c=relaxed/simple; bh=iNcigU8SKKS4UCAyTgtwdz9vnKIHgAnymJ3icWIyHUs=; h=Message-ID:Date:Subject:To:Cc:References:From:In-Reply-To: Content-Type:MIME-Version; b=OxW1nviFcybtTQHD8JlV7JL9eQWJiUDNov6CgRPdMv6TA3IWb+VgnEG1mU09aR+uFE/m5+G+lHrp0QCT28/MyLaJAfv/CXTd2Uzc8vVBwvl3I6ncKey3tr8Zst0doorLg6bS0VeUPS5qw2CfjUNIafgMULvMx2CAyD7LPd3rqec= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com; spf=fail smtp.mailfrom=amd.com; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b=4COAFWss; arc=fail smtp.client-ip=52.101.57.33 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=quarantine dis=none) header.from=amd.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=amd.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=amd.com header.i=@amd.com header.b="4COAFWss" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=lenqgBmgwcLfp/Ogk9ZF8wJsIP3SEvyoLJTqWwzjYTaRiNRitcc6RBo0zQ4gP2ko1js+7acrlxdpva2QQLpaab75A5CDqOsCVfFTgJi4YvS3jktpXMxWtve+8ZMEkXK6po6lS9x+DW6b98SGSFLOJbDyz+YWosGMuObAkLBlH352nKuGB4rsIUdvxRH/T+SL3K/7jbuOVT+C3egJGD0XgrC4axcHaZlYJlJMrWyo4w2kyz4czQevUg2scXQDPpY8WJ2bWeiqSM6gSyw/mKOYhEcvVO4eSATLUbnkIxPq7tTv1597WBszxdgFFBOykmow2PAXeOC6Ak4CQUO2zUbSSg== ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=microsoft.com; s=arcselector10001; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-AntiSpam-MessageData-ChunkCount:X-MS-Exchange-AntiSpam-MessageData-0:X-MS-Exchange-AntiSpam-MessageData-1; bh=xwJHULXrUqe3nJ1D9ShD1Iz5v9mjdwj9roFfAm9+b5k=; b=MqdqFSPUAOBmgy1bbvmiVmSKCO04OszTeoIRv34NY6EwAQRCHE0PxsfaV/RiOOYRlxzAKlrudAl3hXAbepQTs5Uo+TJDBU4TNzkTdr099P2cNh2eOmZLGWbirvI3rqlrfnSXo0bXDHJGtkF/AzLwTaewSVKolTnD/2GFITS+Q2yZMGu0Dwd9CGPm5AOnapXWTfoqZTOqICCi0LaGkhhYNAsnHj9kV3wHYr91du3jRIaSknc6bZip/P7SEiURdomNz8XfpON7BQtnZoFgBPwvB++8Wg2kctP99MZgfmPqUQ829PYJmHfdYsGkL27OAcBeV5pNT19uM/leaCQgVcPUCA== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=amd.com; dmarc=pass action=none header.from=amd.com; dkim=pass header.d=amd.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=amd.com; s=selector1; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=xwJHULXrUqe3nJ1D9ShD1Iz5v9mjdwj9roFfAm9+b5k=; b=4COAFWss5kIw03jr4Ir5xjq/h3xyTV1oiUto3aDEymFLNXeO4uuiSXq9mRA9NZu3I9yGHnnIrgJBGT1V9UwsfA2HOZq+CbcROu4mdQqpklGvRgXXVfJTr+qJas+0mWkMbOH/Lf4n1+XNxZeprxLEhbC0Gq0DQF6dFlY2Inh5yGI= Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=amd.com; Received: from PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) by DS7PR12MB8419.namprd12.prod.outlook.com (2603:10b6:8:e9::20) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.451.16; Wed, 23 Sep 2026 08:03:27 +0000 Received: from PH7PR12MB5685.namprd12.prod.outlook.com ([fe80::ce69:cfae:774d:a65c]) by PH7PR12MB5685.namprd12.prod.outlook.com ([fe80::ce69:cfae:774d:a65c%3]) with mapi id 15.21.0451.014; Wed, 23 Sep 2026 08:03:26 +0000 Message-ID: Date: Wed, 23 Sep 2026 10:03:21 +0200 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v1 1/2] dma-buf: keep DMABUF_DEBUG off by default To: Jianfeng Liu , dri-devel@lists.freedesktop.org, linux-media@vger.kernel.org, linux-kernel@vger.kernel.org Cc: linux-arm-msm@vger.kernel.org, Jessica Zhang , Sumit Semwal , linaro-mm-sig@lists.linaro.org, Rob Clark , Sean Paul , Simona Vetter , freedreno@lists.freedesktop.org, Marijn Suijten , David Airlie , Dmitry Baryshkov , Abhinav Kumar , Karl Mehltretter References: <20260923074256.9357-1-liujianfeng1994@gmail.com> <20260923074256.9357-2-liujianfeng1994@gmail.com> Content-Language: en-US From: =?UTF-8?Q?Christian_K=C3=B6nig?= In-Reply-To: <20260923074256.9357-2-liujianfeng1994@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-ClientProxiedBy: FR4P281CA0315.DEUP281.PROD.OUTLOOK.COM (2603:10a6:d10:f6::11) To PH7PR12MB5685.namprd12.prod.outlook.com (2603:10b6:510:13c::22) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: PH7PR12MB5685:EE_|DS7PR12MB8419:EE_ X-MS-Office365-Filtering-Correlation-Id: 4ea54156-8de6-4d0d-aecf-08df194925c4 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|7416014|376014|23010399003|6133799003|22082099003|18002099003|56012099006|11063799006|5023799004|10067099003|4143699003; X-Microsoft-Antispam-Message-Info: 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 X-Forefront-Antispam-Report: CIP:255.255.255.255;CTRY:;LANG:en;SCL:1;SRV:;IPV:NLI;SFV:NSPM;H:PH7PR12MB5685.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(7416014)(376014)(23010399003)(6133799003)(22082099003)(18002099003)(56012099006)(11063799006)(5023799004)(10067099003)(4143699003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?cGRidzVMOTBkZjNvWDcwSGliZXVyRVBiL3RLWTJkL1FmczNia1NuTjRTbjcx?= =?utf-8?B?U1g2RVRuUjNXZ21kRDJRQms1c01EU3VSTzFkVEoyNUZVZDl0WGthRlBrY2tu?= =?utf-8?B?WVkzeWFUOTNNUnZ3Y0x5Mk8wZDUrMzR6UWs0N09QTjlGZktRU0NlYSszZWlY?= =?utf-8?B?QjVoeEFHcG91dURZMDcvWklZeDR5cXZ4OHkrLzFoTU5mQkpnd1ZseURWakdK?= =?utf-8?B?MnRrMi9QdDM5cXNwQzlCTmh0TlhGbkJsRU1Pd0RFTCs5VVBrVmxtNHdWczFJ?= =?utf-8?B?L3hVVFRoVEQyZU5kMTVkSDNtZmZmS1ZRVFN1YWZkVUhQYWJtNnFYQVJHQWRY?= =?utf-8?B?R1ZSY0RoQ0ROeHhZcERMYkVmSTkrSUNpNk83VjgrWHl5M05Ed2RSQmc3Wmlh?= =?utf-8?B?TndROUx5OSs0ckVZREJtNG1GMlBTdThvbWs5eFlYSE15SFRFQnJZTXJpVU5o?= =?utf-8?B?K2tKVHVqK0VPOWhaZDlwb1ZSOUxjWEdZcldGenFNbVkzclFnVjBOb0MycUhT?= =?utf-8?B?OFdXa1d3ZUF4bytIbG9qeVdMRkljTS9YTzI0MS90NmpKYVBtL3pMbVdCYXh1?= =?utf-8?B?L2R4UFRNbzBPMkVUSjdhQjI3MkVBZHFmbnp2ME1LVXlWYUtoZEpLTGhxZVdJ?= =?utf-8?B?QWxsd3J3bHl3ZDluZkNUajI2d3prZ1MxTUM3dnBTVUVyK0NhVDZueHdnRHJ2?= =?utf-8?B?bjR5eFdSNmNHMkFUbkdOeEpNVlYvVkVWcWNvcU9wR3IyenlxS0QyUTVUaTdO?= =?utf-8?B?dFlZVUU2cmdWQXc1SlY1UlE0NmI1NENtbDNNaUdiKzhtTG1rM0RhRDBMWTBB?= =?utf-8?B?TzlKVG1HV2YwM1NpbzNIY2pqRk9iaGpsaFNDdkFDdzlPdndVb1Avd05UVkNk?= =?utf-8?B?aVh2enI1Y1UrQkN2djhuSHEybWxKK3R1UW1tMzZRWHAyOUVQbWF2VDdMd3hZ?= =?utf-8?B?UkFyZnViSFk4VUcvcWovSnhhQU1jakVGYXFvbnNUaWJWVVcxQXRIbVZLTUh2?= =?utf-8?B?Y2RzTlZLT2FxZWhtTUlJUlROZUNPNTVGZ0R1MlB3VXRMbVFoN2ZrdkRJNHBp?= =?utf-8?B?Qlh2Vmt1ZTZqN0s0a0I2UFJHYTloa0kyWk50a0Q2RXcrZ0NwOU1iYkU2UWFW?= =?utf-8?B?TENWUEgxSGgwak1HaktXbUlUNXNOempid2FFUFdSNkxuZEF0N1hROUZBTWtN?= =?utf-8?B?UXlrTWhzaEtia2pKREdMc0s5ai9SeTR4VjlqaXVtMkFYRnQzeTdka29DNjlF?= =?utf-8?B?Z004eUZqbXFiYVRaTkhjVzNGSlBSbXlWV0hjcTFkZGszYjk2L2syeWtJTUtV?= =?utf-8?B?UTFTTzl1bU9aZWttNE9jUUVEdmxITS9mbGpGYk9lbkpIQ0trWjE3K0RmUmtQ?= =?utf-8?B?ZDd0UDE1S1RucHc4WFlmS0FFUzd3RFFLYVRBYUZhV2ZIY1dHZlhZcEJjdE5k?= =?utf-8?B?UG9VT0psRDJYa3I3YXJkRGhzV09uOVB1TU1xdUdhK2ZZaFBSL0h6VnFTMUVN?= =?utf-8?B?QktEWElZalZnZ3JWMW1XTDgzWkRaK0JNcDhuTU9OLzI1Q1VwRkpZaFNPYzdS?= =?utf-8?B?THY5NTFZcmVObEo0dlFldUpvMUtPaWoyWHVaL20rZFBLZWQ5UENEbjg4NWRw?= =?utf-8?B?ZHJRWFZseGZ4OHl1RDlGRk4yNGE5bTlFV0o1cDNSZjljN1RRc2NQVitGUm9x?= =?utf-8?B?TXBzcmRuT1NNQWVpR1JEUEFBZk1tcEsydEZ0N3hwZFFCcFZ3c2lab1ZpTkEz?= =?utf-8?B?QVd2L2pJRkhsTTdCZzVRZkpLbWR3bEpucEI0YmJ2MWdlYTVhZGRFbFJIb3l4?= =?utf-8?B?QTZSbUlEb2p3aTBVVDk5VGV0N21NS2pvcUJqMCtoTTRxaWVINy9iRVd0TDUx?= =?utf-8?B?enN3VHU1YjN2TDdRVTYvVUc0MzUzNkJMUFlLN0dvNkFxS1JoYU5KVWUvSWZz?= =?utf-8?B?RWxGTWtzcmg2QUlGS3dNMFIvNE1DcGxZWTdXRDJxQWMwVXRoNHB2dlArQlUx?= =?utf-8?B?eU40eGlST2ZTQjVtK3VSaWc1MUVJQXRNQWR6NERUbXpEMWx5MzNDcEtKUmJ5?= =?utf-8?B?SUtSM2dxUTdtRjd2VzU4bEg1U3IrbG5KQ3JkWTA5Z1plUForYjNJUmpKMGJh?= =?utf-8?B?YkhlNDhuTEp2YXpmSEVvb0tZS1JQN0U2WU9yOUdBR25xcGZranlobCt2Y3Zr?= =?utf-8?B?dGJDOXlLdzdqekFsSkoxNWJJQXhYSzYvSkQ0d1VVa0EvbDRuOFJZbkZ1Y0I2?= =?utf-8?B?S3RndUxrS21uNGV3MGZSVHg5cThjazJrbEpMR0RjL1dLZXFpNGE3QUFqRjRw?= =?utf-8?Q?tUAreIR3hLYCCAjWRE?= X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-Network-Message-Id: 4ea54156-8de6-4d0d-aecf-08df194925c4 X-MS-Exchange-CrossTenant-AuthSource: PH7PR12MB5685.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 23 Sep 2026 08:03:26.8371 (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: JEMman8ulaQugxz95TQ0xYcyHXIDpICzT/FxljpBxoqrlJfyFQ6pMqIAeCLcRF2R X-MS-Exchange-Transport-CrossTenantHeadersStamped: DS7PR12MB8419 On 9/23/26 09:42, Jianfeng Liu wrote: > [Sie erhalten nicht häufig E-Mails von liujianfeng1994@gmail.com. Weitere Informationen, warum dies wichtig ist, finden Sie unter https://aka.ms/LearnAboutSenderIdentification ] > > Commit 143755bdabaa9 ("dma-buf: Make DMABUF_DEBUG default to y on > DEBUG_KERNEL kernels") fixed a dangling reference in the DMABUF_DEBUG > default, which had the side effect of enabling the option (and with it > the page-stripping sg_table wrapper handed to importers) on every > kernel with DEBUG_KERNEL=y - i.e. virtually every distro kernel. > > drm/msm is broken by this: it maps imported dma-bufs into the GPU's > own pagetables with iommu_map_sgtable(), which needs the struct page > of the attachment sg_table, and it fills the GEM object's page array > through drm_prime_sg_to_page_array(). With the debug wrapper in > place both silently produce garbage (the wrapper zeroes sg->length, Interesting point, we should probably change that. > so the page iterator yields nothing and an uninitialized array is > kept). The VM_BIND map job then fails asynchronously after userspace > has already enqueued GPU work referencing the mapping, which shows up > as an arm-smmu translation fault from UCHE, e.g.: > > gpu fault: ttbr0=000000088a889000 iova=000000010741c000 dir=READ > type=TRANSLATION source=UCHE > > This breaks hardware video decode (clapper, chromium) on Adreno > systems; bisected on a Snapdragon laptop as v7.3-rc3 good, > v7.3-rc4 bad, culprit 143755bdabaa9. > > Revert the default until importers that legitimately need to build > phys-based mappings have been converted. Well that won't work like this, pointing those things out is exactly what DMABUF_DEBUG is made for. What MSM is doing here is not allowed at all and can break badly. We gave drivers 5 years to get that fixed and I'm now pushing for completely deprecating that hack. See patch 84335675f2223cbd25d0de7d38ecc7d40b95bd4a: Author: Simona Vetter Date: Fri Jan 15 17:47:39 2021 +0100 dma-buf: Add debug option When MSM needs the struct page then it must import a shmemfd and not a DMA-buf. What we could do is to either fix MSM or mark it as broken. Regards, Christian. > > Fixes: 143755bdabaa9 ("dma-buf: Make DMABUF_DEBUG default to y on DEBUG_KERNEL kernels") > Signed-off-by: Jianfeng Liu > --- > > drivers/dma-buf/Kconfig | 9 ++++++++- > 1 file changed, 8 insertions(+), 1 deletion(-) > > diff --git a/drivers/dma-buf/Kconfig b/drivers/dma-buf/Kconfig > index e4f078a326a41..b3c581ef4c987 100644 > --- a/drivers/dma-buf/Kconfig > +++ b/drivers/dma-buf/Kconfig > @@ -43,7 +43,14 @@ config UDMABUF > config DMABUF_DEBUG > bool "DMA-BUF debug checks" > depends on DMA_SHARED_BUFFER > - default y if DEBUG_KERNEL > + # NOTE: keep this default n. The page-stripping sg_table wrapper that > + # this option installs for importers breaks drivers that build a > + # second-stage IOMMU mapping (phys -> iova) from the attachment sg_table > + # and therefore still need the struct page, e.g. drm/msm with its > + # per-process GPU pagetables. Until those importers are fixed, making > + # this default y breaks hardware video decode and GPU workloads out of > + # the box on affected systems. > + default n > help > This option enables additional checks for DMA-BUF importers and > exporters. Specifically it validates that importers do not peek at the > -- > 2.47.3 >