Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Subject: Re: [PATCH] swiotlb: set IO TLB segment size via cmdline
To:     Roman Skakun <rm.skakun@gmail.com>
Cc:     Andrii Anisov <andrii_anisov@epam.com>,
        Roman Skakun <roman_skakun@epam.com>,
        Jonathan Corbet <corbet@lwn.net>,
        Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
        Michael Ellerman <mpe@ellerman.id.au>,
        Benjamin Herrenschmidt <benh@kernel.crashing.org>,
        Paul Mackerras <paulus@samba.org>,
        Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
        Boris Ostrovsky <boris.ostrovsky@oracle.com>,
        Juergen Gross <jgross@suse.com>,
        Stefano Stabellini <sstabellini@kernel.org>,
        Christoph Hellwig <hch@lst.de>,
        Marek Szyprowski <m.szyprowski@samsung.com>,
        Robin Murphy <robin.murphy@arm.com>,
        "Paul E. McKenney" <paulmck@kernel.org>,
        Randy Dunlap <rdunlap@infradead.org>,
        Andrew Morton <akpm@linux-foundation.org>,
        Thomas Gleixner <tglx@linutronix.de>,
        "Maciej W. Rozycki" <macro@orcam.me.uk>,
        Muchun Song <songmuchun@bytedance.com>,
        Viresh Kumar <viresh.kumar@linaro.org>,
        Peter Zijlstra <peterz@infradead.org>,
        Lu Baolu <baolu.lu@linux.intel.com>,
        Mike Rapoport <rppt@kernel.org>, Will Deacon <will@kernel.org>,
        xen-devel@lists.xenproject.org, linux-mips@vger.kernel.org,
        linuxppc-dev@lists.ozlabs.org, linux-doc@vger.kernel.org,
        linux-kernel@vger.kernel.org, iommu@lists.linux-foundation.org
References: <20210914151016.3174924-1-Roman_Skakun@epam.com>
From:   Jan Beulich <jbeulich@suse.com>
Message-ID: <7c04db79-7de1-93ff-0908-9bad60a287b9@suse.com>
Date:   Tue, 14 Sep 2021 17:29:07 +0200
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101
 Thunderbird/78.14.0
In-Reply-To: <20210914151016.3174924-1-Roman_Skakun@epam.com>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 7bit
MIME-Version: 1.0
X-MS-Exchange-MessageSentRepresentingType: 1
Received: from [10.156.60.236] (37.24.206.209) by PR3P193CA0051.EURP193.PROD.OUTLOOK.COM (2603:10a6:102:51::26) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.20.4523.14 via Frontend Transport; Tue, 14 Sep 2021 15:29:09 +0000
X-MS-PublicTrafficType: Email
X-MS-Office365-Filtering-Correlation-Id: 074dfc55-95fb-49c7-e925-08d977946657
X-MS-TrafficTypeDiagnostic: VI1PR0401MB2334:
X-LD-Processed: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba,ExtFwd
X-MS-Exchange-Transport-Forked: True
X-Microsoft-Antispam-PRVS: <VI1PR0401MB2334A539B4FCAEFF4E2FA551B3DA9@VI1PR0401MB2334.eurprd04.prod.outlook.com>
X-MS-Oob-TLC-OOBClassifiers: OLM:9508;
X-MS-Exchange-SenderADCheck: 1
X-MS-Exchange-AntiSpam-Relay: 0
X-Microsoft-Antispam: BCL:0;
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:VI1PR04MB5600.eurprd04.prod.outlook.com;PTR:;CAT:NONE;SFS:(346002)(39860400002)(366004)(396003)(136003)(376002)(6916009)(86362001)(66946007)(966005)(16576012)(38100700002)(186003)(316002)(5660300002)(6486002)(83380400001)(7406005)(7416002)(478600001)(54906003)(66476007)(66556008)(4326008)(31696002)(2616005)(53546011)(36756003)(956004)(2906002)(8676002)(31686004)(26005)(8936002)(43740500002)(45980500001);DIR:OUT;SFP:1101;
X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1
X-MS-Exchange-AntiSpam-MessageData-0: =?utf-8?B?aXpaZmNvUjZVNWNjVGhZcVJFZzJqR25PcGR4bjgvcmFQMDZ4a1pCdFZVNDN1?=
 =?utf-8?B?d0dlenhXMXp4cVpaT283UGNtc0NPZXpHY05SRmtxc2RTZ3B5NElLaGhocXVL?=
 =?utf-8?B?SWszUmY5MDZaNlNtajljYmZMMU1MWDl4UnZwSHk1QUEvbXBBa1Q2cWtHRDBL?=
 =?utf-8?B?TjdFUEVpNThPVFNxMkc1ZVk0NHpFcDNYdTY3Y2pOSkNUWmJNQWkvNStld2V6?=
 =?utf-8?B?R3J1YmFDaWtvZVVVc2ZXakJRYXlFUjZGSU1MYmdaQXZjTDJ1NS9Ra3ZGelNa?=
 =?utf-8?B?TW5WR2JIR0Q0ZUgxaXRHaWcvaytsRUpVQUk4SFl0Vnl4QjQxQUk1VGhBZGg2?=
 =?utf-8?B?ZW54dmJCMGtVOWdpUVNDdUg1eXNsMEZNY0N3S1Z2Rko0RWcxdnhKY0lnOU5L?=
 =?utf-8?B?WXA3a1ZTdUhNQUFHNmpjMFZiMUhsUjZtVzN2L0ZzOGR3VzBEaXU1NHJnTWo3?=
 =?utf-8?B?aGJxbFMvN2dFVXl2T2tQRXpHUUY0K3JFby9JUzBnM3dvRkgza2YzSS9vTUtI?=
 =?utf-8?B?WjhSQ2Z1aHBGREJHekRucm1lUFVuMWEzY0NYdFdJNVE0alg1YjhDRXRFWHBx?=
 =?utf-8?B?UW4yTHk4QnVFKzNjOUE0eFZLQ29TYkNMSHdHekpzSFdPNWw5cXBMYjdwK3F1?=
 =?utf-8?B?dG8rdjlrUm51RDBnUGV2a3QyQUFoWHRyWFdQUHdGYVRyZ09rZTJkSHVVT2RQ?=
 =?utf-8?B?K1Fuc0FBTFprMUJXTzhpbktDLzNNeWkzVDkzV0NaTFNDTTd2THMwZ3BTcFZh?=
 =?utf-8?B?TVVYL25rMVFyTFdzSDVJOU1PVWRxTHJ1OUQyaTQ2dVNSNVBHd1RPMm50OUpR?=
 =?utf-8?B?WDcxNWhKbHRDREgzdHNzbGlESkZsNU5ZU2VDandSQ2o0OGlOWG54K3pDZ1Jr?=
 =?utf-8?B?Wm5qc3d6Q05oY0pUVlo5bm05azROL3lDNWRKckIxdUM1TmtWYzVMakF3NVVo?=
 =?utf-8?B?d2dteUN5Skt1N09KSndoZG9vRW5oUVE2blgrSmFuYTIvc3ZVQ3AwRytYa0Jh?=
 =?utf-8?B?aU1tVmRsMEdxN0NsL0ZJai9UNHBwU0hHTTJ0STZWaFlWV2RmZGZ0SmtpYkdh?=
 =?utf-8?B?TXYyOTJwdnVJVXI1RUN5OEdIT0E5Vk1iZTZab3pJaTUxR0JaN2tSNlM0MjN3?=
 =?utf-8?B?cEdEWmlCSWk2cXlGNVV4eFlGNHhYdThpV1BXWW9pRzh5cTRhUEI4M1pYVU9x?=
 =?utf-8?B?REFJSUlva05mTERKRkw3d0Y4QTZQS2hQSFdkUkRBQXJZcG95T2Q0VkhzL1dJ?=
 =?utf-8?B?NmxzRjA0VGcrU3Y5VDVKSjA1UFBQNHdBYXF5SUNrdzBiZ2F1cGQrODR5ZnRK?=
 =?utf-8?B?ZW80K0J0aFh4ODBCU0VkbXZqeXlhQW1WcndSRW53UVlZaUduWFJrSWhwcmJN?=
 =?utf-8?B?Q21XcDk0Um5lNTVHdnpKeXdjcU4wV3Q3YjhyL3JyZ2NFdUdLbUZBOEpBTG1I?=
 =?utf-8?B?bC9LcmZEblJwYlBQd2hBS2Fza0pRSHVlSkN1THdoSFJKUXBDa28yR0s5dXpr?=
 =?utf-8?B?V0FmWDhtZ2s1aHJxSFVsUTJRWUg4aktIV282MU0xeWhKL2tFV3h5V1JUNXVx?=
 =?utf-8?B?SUNSaEdVdFIvTTkra1pxSld4VFAxZ05XMklTTU1wSGhPSWM3c3hCdkJXVjlr?=
 =?utf-8?B?UzhOdXJwSTdhNkxCYlBHVi9vV3dpUis5dFpOd2VreFlJK3N0L241OHFkMEx1?=
 =?utf-8?B?QWpZODJpUFBXLzRHZEZUeHJpdXh5bUgva3JZS25HV3hMdmszelQ2VVRjbThp?=
 =?utf-8?Q?EHtteRfnHGiG4VVIJeSMsg07Np7Q1JnvbOEPUBb?=
X-OriginatorOrg: suse.com
X-MS-Exchange-CrossTenant-Network-Message-Id: 074dfc55-95fb-49c7-e925-08d977946657
X-MS-Exchange-CrossTenant-AuthSource: VI1PR04MB5600.eurprd04.prod.outlook.com
X-MS-Exchange-CrossTenant-AuthAs: Internal
X-MS-Exchange-CrossTenant-OriginalArrivalTime: 14 Sep 2021 15:29:10.7377
 (UTC)
X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted
X-MS-Exchange-CrossTenant-Id: f7a17af6-1c5c-4a36-aa8b-f5be247aa4ba
X-MS-Exchange-CrossTenant-MailboxType: HOSTED
X-MS-Exchange-CrossTenant-UserPrincipalName: kXdQssFPz9rIrTB1YSXP35DiSNUdVE4BfSOJKHu3+j7Ku5TB+6FgftUS2/Mi3A3sAouc4CUWJBS2Nck1t6XQaA==
X-MS-Exchange-Transport-CrossTenantHeadersStamped: VI1PR0401MB2334
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On 14.09.2021 17:10, Roman Skakun wrote:
> From: Roman Skakun <roman_skakun@epam.com>
> 
> It is possible when default IO TLB size is not
> enough to fit a long buffers as described here [1].
> 
> This patch makes a way to set this parameter
> using cmdline instead of recompiling a kernel.
> 
> [1] https://www.xilinx.com/support/answers/72694.html

I'm not convinced the swiotlb use describe there falls under "intended
use" - mapping a 1280x720 framebuffer in a single chunk? (As an aside,
the bottom of this page is also confusing, as following "Then we can
confirm the modified swiotlb size in the boot log:" there is a log
fragment showing the same original size of 64Mb.

> --- a/arch/mips/cavium-octeon/dma-octeon.c
> +++ b/arch/mips/cavium-octeon/dma-octeon.c
> @@ -237,7 +237,7 @@ void __init plat_swiotlb_setup(void)
>  		swiotlbsize = 64 * (1<<20);
>  #endif
>  	swiotlb_nslabs = swiotlbsize >> IO_TLB_SHIFT;
> -	swiotlb_nslabs = ALIGN(swiotlb_nslabs, IO_TLB_SEGSIZE);
> +	swiotlb_nslabs = ALIGN(swiotlb_nslabs, swiotlb_io_seg_size());

In order to be sure to catch all uses like this one (including ones
which make it upstream in parallel to yours), I think you will want
to rename the original IO_TLB_SEGSIZE to e.g. IO_TLB_DEFAULT_SEGSIZE.

> @@ -81,15 +86,30 @@ static unsigned int max_segment;
>  static unsigned long default_nslabs = IO_TLB_DEFAULT_SIZE >> IO_TLB_SHIFT;
>  
>  static int __init
> -setup_io_tlb_npages(char *str)
> +setup_io_tlb_params(char *str)
>  {
> +	unsigned long tmp;
> +
>  	if (isdigit(*str)) {
> -		/* avoid tail segment of size < IO_TLB_SEGSIZE */
> -		default_nslabs =
> -			ALIGN(simple_strtoul(str, &str, 0), IO_TLB_SEGSIZE);
> +		default_nslabs = simple_strtoul(str, &str, 0);
>  	}
>  	if (*str == ',')
>  		++str;
> +
> +	/* get max IO TLB segment size */
> +	if (isdigit(*str)) {
> +		tmp = simple_strtoul(str, &str, 0);
> +		if (tmp)
> +			io_tlb_seg_size = ALIGN(tmp, IO_TLB_SEGSIZE);

From all I can tell io_tlb_seg_size wants to be a power of 2. Merely
aligning to a multiple of IO_TLB_SEGSIZE isn't going to be enough.

Jan