From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 071BECD4F3D for ; Thu, 21 May 2026 04:25:20 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender:List-Subscribe:List-Help :List-Post:List-Archive:List-Unsubscribe:List-Id:MIME-Version:Content-Type: Content-Transfer-Encoding:Message-ID:Date:Subject:Cc:To:From:Reply-To: Content-ID:Content-Description:Resent-Date:Resent-From:Resent-Sender: Resent-To:Resent-Cc:Resent-Message-ID:In-Reply-To:References:List-Owner; bh=R2jeQp593tQI+raRY8n8eSHWl4GbwSn6C6eo/IUr1Co=; b=kpxVD56wRsZM0wtD2EPns0V2Fm 0XMydH00ImASSji0WrCVgzkpLgQo8/icpv7e+/BVtbKXhCU9uuhgz5060/6/3XHSG9Y5OXkeBmWrZ KYCNUfGVN0FlrpoZp3CO6AQaaOYh01i5c9DW0gW/O5ZygSvgu8fFNrrqQe2HMR/H9d4LYqwNWdFdj PBshCIKoYRI1B2wnK2Pd2jbjh7XwKOhkMHjH3Ul7MzvYcUJ8yTefltTuBOMfkSAJjAegUOLPuUnkj yRc6Awde6/qoCcBFlZvqxTyFXOJflorAzVnQNVzGEdmK73hDZodcBTv5CJYBKOa5s0/9bgA2DfnpP NCONAKpw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.99.1 #2 (Red Hat Linux)) id 1wPuy9-00000006eYe-0XXa; Thu, 21 May 2026 04:25:13 +0000 Received: from mail-southcentralusazlp170110003.outbound.protection.outlook.com ([2a01:111:f403:c10d::3] helo=SN4PR0501CU005.outbound.protection.outlook.com) by bombadil.infradead.org with esmtps (Exim 4.99.1 #2 (Red Hat Linux)) id 1wPuy6-00000006eXw-30mD for linux-arm-kernel@lists.infradead.org; Thu, 21 May 2026 04:25:11 +0000 ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=MC3y+fc43v9oDeEevyicRx8525/qJvUVVhhjZ498ApK9PIN6h9VqGn7n4FRZBpihaUg09PcJGFevr6u5QPMUXVx0Um6SyLveEn+9uYKo9zw0j3OnPDVfQgoEcHBSok4pjTVluzLPwMnCC4MWjxSxCMRJ6MUBwLprEpI79KdnWvl+jqUe8uH6V/Ih2dgQu7ZAHzh6ycxSjPB7lYIWxjz41xqjnr2esrFLJPGg1eBnm0vJ/WW/fqj7wMLq/vRR1mYIIiusaqtiMx6zFN+FnDmjkJjgvCiuPoGQRW3nf8KjQKyYf6N8ZJ68RNbU7s+ISIVEsIWCPpY6eX47kc6DU0fDIw== 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=R2jeQp593tQI+raRY8n8eSHWl4GbwSn6C6eo/IUr1Co=; b=CIo9gR2sE3/Xcx+P8QaY67HrS8/g5ekFKFenYulE4m/3XCZA2x4h08TTxh2K65ipyzCZSrLWox8gSlggbLedO/fcSClGFozy1U7SrxW8E3Ns0dSlibMPKp2/1/hMO/4JIy+aNGRfRAHRULlp996xz5EW+l0LOHtzf7vlQHZ7DRcnCJa8zs3xtQcGpMLGF43nuFnroz6p3KaV5YtTbcxnw13YDnVkJ6egxn+qumj9Dmyh/u+2Oup52OjltIHA25+sBroNRqXkDikNPmvUNRL96Rp/qMDCl4jTDnWVgaoDYhdgRtT/qAnBH13hMOCt9Ko6SaK2TwxQLqmThGvTp5D2AQ== ARC-Authentication-Results: i=1; mx.microsoft.com 1; spf=pass smtp.mailfrom=nvidia.com; dmarc=pass action=none header.from=nvidia.com; dkim=pass header.d=nvidia.com; arc=none DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=Nvidia.com; s=selector2; h=From:Date:Subject:Message-ID:Content-Type:MIME-Version:X-MS-Exchange-SenderADCheck; bh=R2jeQp593tQI+raRY8n8eSHWl4GbwSn6C6eo/IUr1Co=; b=q76hCqbQXoFt361Bgd4xVHK1oTPno4mRdWvteVKR0YHdyMlRgw6V445t41l4H2J0LXwBH1PTKOH5D1WIXAKg3gYNcltEOec/Tha7Puw22nPxEnI/RLGc6QwO8tXtsJzTmPxYVu6R1zUSgE7CeVmnUp6zFg5g6JJRg58YKzd6mPqrKGLg1eRKym/GGLEkzMPp6D6P7JR8okqkAixNWjpFZwiX4DrjI36tBTIOV4JY6uN7JjQruuqiMusf9WniVkMAcsYSyfiwMrJZEiBGAvFgaW6mPSLqE33ZyRJOlN1gsrTSDp1ciRZ/6p6cBgfvHRekH6LT/tdZ1qx+jMY2/KiZRQ== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from DS0PR12MB7726.namprd12.prod.outlook.com (2603:10b6:8:130::6) by SA3PR12MB8022.namprd12.prod.outlook.com (2603:10b6:806:307::7) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.48.16; Thu, 21 May 2026 04:25:04 +0000 Received: from DS0PR12MB7726.namprd12.prod.outlook.com ([fe80::5807:8e24:69b0:f6c0]) by DS0PR12MB7726.namprd12.prod.outlook.com ([fe80::5807:8e24:69b0:f6c0%4]) with mapi id 15.21.0048.013; Thu, 21 May 2026 04:25:03 +0000 From: Alistair Popple To: linux-arm-kernel@lists.infradead.org Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, catalin.marinas@arm.com, will@kernel.org, david@kernel.org, anshuman.khandual@arm.com, ryan.roberts@arm.com, dev.jain@arm.com, balbirs@nvidia.com, jhubbard@nvidia.com, Alistair Popple Subject: [PATCH] [RFC] arm64: mmu: use range based TLB flushing when hot unplugging memory Date: Thu, 21 May 2026 14:24:26 +1000 Message-ID: <20260521042426.2128731-1-apopple@nvidia.com> X-Mailer: git-send-email 2.54.0 Content-Transfer-Encoding: 8bit Content-Type: text/plain X-ClientProxiedBy: SY5P282CA0169.AUSP282.PROD.OUTLOOK.COM (2603:10c6:10:24a::11) To DS0PR12MB7726.namprd12.prod.outlook.com (2603:10b6:8:130::6) MIME-Version: 1.0 X-MS-PublicTrafficType: Email X-MS-TrafficTypeDiagnostic: DS0PR12MB7726:EE_|SA3PR12MB8022:EE_ X-MS-Office365-Filtering-Correlation-Id: b46be326-14c4-499a-74b5-08deb6f0edcc X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|1800799024|366016|376014|18002099003|56012099003|11063799006|6133799003; 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:DS0PR12MB7726.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(1800799024)(366016)(376014)(18002099003)(56012099003)(11063799006)(6133799003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?+ydSm/uPEwH+nYE2o0Q4zn4vN2E/WJA3fpf7gXolAMVspBA2AA4iRVsgf6py?= =?us-ascii?Q?TBmbYVsOd5c97orMN+G54JJyvcTmgMtC7DXRCvSShwc23VfhKUJC5U3QFhd5?= =?us-ascii?Q?NSbLR2boBNqMGBDliGfsd6Tr1ZawcCDkMVAwDPXwC7NhlCKW9k/VSuRhF9NT?= =?us-ascii?Q?+Njpm65TPtQrmhLpZ5EApXVICjEnkHGU2T5C+W+ZClR/bwgB4m2uM/4XlUWM?= =?us-ascii?Q?6MTV9YjUEokb78VktDCx5LNpsC8DHDBjPBf/T0Sc9qtaoyeSXo+lckooVdnm?= =?us-ascii?Q?sx3Y1fdhdVJWaagXye4VSCjfTfCSilhVv3vQ+L+PzKRHF73/EuUgJ882scXr?= =?us-ascii?Q?Hl5r1GFWJldFDGVvRD8s9Jbrg3e5t9DLPCMiZxZd6+7T1YjCutohyv/WMNlp?= =?us-ascii?Q?NZhWdKzxtKQRBcduoSsDPjGRz3zbHqPAoUnj/GZQmUkLYhNm4WB/nqnemRJV?= =?us-ascii?Q?UdmKVECzaG8VtugcTgFRgZBtLpVVEUbg+Sy2xv/XJ48KV6+2TM647KsGojuo?= =?us-ascii?Q?IsFEDrD9leTKxh4KE6g7o6TOAwrJLz2QKOO8bk5BdAuBFCcgi6Dk55Kghhit?= =?us-ascii?Q?ZetlSzIuLP/YG8dNh9zMbPSZZV0AF8ajMPuRiBI62RG4U7h3Sd0sImhw2pgp?= =?us-ascii?Q?/Q8EsS6NJ5lx3X79MD6eqxYO5vQ54lCgzp1XvUZ1NR2sOXtFTMr3DlD5w78w?= =?us-ascii?Q?lPqcciv6pHOcqdQm8DSAehuu4eBlytn4hW+3twvFQxwd46l0udVvujssA2pB?= =?us-ascii?Q?FfWKVEO4GoDzct4nh+PtrZZX5KV+CJ60WOJLXsA9v38ECo4K10xBsBy+wC8M?= =?us-ascii?Q?ncS5zgnwpKUzVnanVFiQFVwREYt4UYR+AvsoJYM3w9Vvcsa/1yUpLfKb60oX?= =?us-ascii?Q?Xi+b03PcP/t/LWq4v6e86YP/TgscUyw2UF4+fZQhuseiNg2cqDXygIqLapp+?= =?us-ascii?Q?Pd2EdpV4eDNHxK0KHibjWGTt+F6ciofVa8FACqr8MHfBFHb4BKksIirWL6Wq?= =?us-ascii?Q?YuxM9WRT1lgG4luiqbEmvtsOjx08E40loR6d0H5EHPrMeiVYhqgbutiKpFoq?= =?us-ascii?Q?2XCXBFSWjDk4C6H4blTtCxmNCdcDs6S2iDsK0KH/wDZjmGwkZr7E74xgW6s9?= =?us-ascii?Q?TssIlN28ai+U59ha7wvAfu6hudLHKPKjdGeLFhXXmkt463apPjCn/+0iaBYk?= =?us-ascii?Q?luTQkxMd3pEws06QhkcWhbtB/8Q620JbJD1tofnrXNSMPw9XwCGf9cPBT2xA?= =?us-ascii?Q?dg6jsT64d5ZU/2maxwz/bjNouSH9/wm2OPFYkA1+AGD7to3PetCuAw8r+KTV?= =?us-ascii?Q?2e+OXPwLKBpi5mIxT465nw+to7Mv9C1nUfdV4I0FWIreLupuUGRzQphZMG1M?= =?us-ascii?Q?Qazzs3AXenstjAzhiO50BBtnZV7BIoIfNMjAgZ+1PDn4KhvFdhkGsmkuMche?= =?us-ascii?Q?oMGasSsHNGoasLhZ5+ztNiBtF3+2HfOSS54O7ZmyWCSmYa7HHVj7ExWhbdPP?= =?us-ascii?Q?k3KtCK2cU1yI5jd0qQX+5BXjNyh62Xu71i64UabFtBmyHVTGJ4tnxC9bLhGV?= =?us-ascii?Q?nx1hTqjFwPVDB+r6Go9TxYSYyhXC283i5Nx98XQTC1jiKqKXSxT5pdpSreF3?= =?us-ascii?Q?8Nzid2PGeDsNhnuqfiEUIIo0J5efqLoBj2nmFvTthaCSnX1j4FQ3ZRN81wj7?= =?us-ascii?Q?wz63zEhufC47oWbYD28J0ZpbPzv3HK7DydMVIYCksRdNK2RLh8SJiXsC8l2I?= =?us-ascii?Q?t8NfXT48hQ=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: b46be326-14c4-499a-74b5-08deb6f0edcc X-MS-Exchange-CrossTenant-AuthSource: DS0PR12MB7726.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 21 May 2026 04:25:03.2890 (UTC) X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 43083d15-7273-40c1-b7db-39efd9ccc17a X-MS-Exchange-CrossTenant-MailboxType: HOSTED X-MS-Exchange-CrossTenant-UserPrincipalName: nydznYeHvUOivmyAQ+gpJZ2Nqh4cUJmTptGFTEWl34i07TOecugcFYJDHfGpRd94YimYd13qonJdPAjZMMd0Zw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: SA3PR12MB8022 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.9.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20260520_212510_769900_2BF1D3FB X-CRM114-Status: GOOD ( 18.13 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org Hot unplugging memory on ARM64 requires a TLB invalidate after unmapping the page to be hot unplugged from the direct map. Currently that happens one page at a time, meaning range based invalidates cannot be used. The result of this is that removing large amounts of memory takes a long time and in some cases can trigger an RCU stall warning. For example on one system hot unplugging 480GB of memory takes ~1 minute. With this change the same operation took ~1 second, a 60x improvement. Signed-off-by: Alistair Popple --- This is an RFC, because I'm not sure the change is correct as it frees the PTE page before flushing the TLB. I'm not familiar enough with ARM64 architecture to be sure this is safe, for example I don't know if HW can update PTE bits such as access/dirty in the page through a stale TLB entry. If so this would open a window during which the page is free but could still be written to. Likely the safe option would be to collect all the pages to be free on a list and free them after doing the range based TLB flush, but wanted to get feedback on the approach before implementing it which is the goal of this RFC. --- arch/arm64/mm/mmu.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 0c24fe650e95..75c773232c14 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -1459,11 +1459,12 @@ static void unmap_hotplug_pte_range(pmd_t *pmdp, unsigned long addr, WARN_ON(!pte_present(pte)); __pte_clear(&init_mm, addr, ptep); - flush_tlb_kernel_range(addr, addr + PAGE_SIZE); if (free_mapped) free_hotplug_page_range(pte_page(pte), PAGE_SIZE, altmap); } while (addr += PAGE_SIZE, addr < end); + + flush_tlb_kernel_range(addr, end); } static void unmap_hotplug_pmd_range(pud_t *pudp, unsigned long addr, -- 2.54.0