From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from CH5PR02CU005.outbound.protection.outlook.com (mail-northcentralusazon11012030.outbound.protection.outlook.com [40.107.200.30]) (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 5AE3918C008 for ; Tue, 7 Jul 2026 22:58:06 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=fail smtp.client-ip=40.107.200.30 ARC-Seal:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783465087; cv=fail; b=nLtERC7wIYZymeI9PL9IzusOVdx+KU3ot+ljz8wecoyp2a1chtaED8GUFqqNZN6EUohO1uf2ayOyqUBRiYuJknK4dACbq9rxZ/6jCdPN1EIrwqcn7OI6F8VlhpjhMhSvU5mlGT4C0MPrL/vmg9TUWYTbAYv5fPQ2x7p2IoLPwVE= ARC-Message-Signature:i=2; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1783465087; c=relaxed/simple; bh=VL2XtWBaSjC1f7r3pis4Qb4orkiNmYveTiM/CLYN/fI=; h=Date:From:To:Cc:Subject:Message-ID:References:Content-Type: Content-Disposition:In-Reply-To:MIME-Version; b=j3fQ5ysLrDznnqBH/KS9/7/nU7axRHoBttYnEH6AYvpwvqsodtP2e2lR9XianSXYhgSzVDG0DxH6lUfUG0P5ODtWeWTCL8dKTG7HTGUiYfFFU4GBHtrDPUx+T+63rExR0rneZesX/h9RThmZXWEEqEbLs3Xmp7zfQbmbnIUFcXs= ARC-Authentication-Results:i=2; smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com; spf=fail smtp.mailfrom=nvidia.com; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b=NMMqPOgt; arc=fail smtp.client-ip=40.107.200.30 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=reject dis=none) header.from=nvidia.com Authentication-Results: smtp.subspace.kernel.org; spf=fail smtp.mailfrom=nvidia.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=Nvidia.com header.i=@Nvidia.com header.b="NMMqPOgt" ARC-Seal: i=1; a=rsa-sha256; s=arcselector10001; d=microsoft.com; cv=none; b=i5IbRRBu/pNMnztlx3dCr7wzEm1vHRt7//WQtX59fC4v+wulTzIAsEfDI7FFMjbLt1B2amZSpzXekBT3uTJuNc48W8iiwlV/T9I8C2zKPceA0Hx5OcW1PMtqA2d8vvJt2e+7jfNXIBCwcEc5jIS2oY6vYsyqp8kueeG7ZAEmLqEMEc5ILuspdYMOtwH3n4mgco1p0IjcjNjDTE2p70aDHU3i1Fel1x6M6WgZ3Yg3huJ6lr+WaCWJzefuo+2bxdmlmcazouWN7Fuwies52D3Ruzv5tKahkTNW71e/b+mWDK1cYQT1Zizz/gQw9I1ZkzgRg9NGj6qxteR4lXPwnV1pRQ== 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=BSwYgSCuGhydm7SW28wLKtBsLt0mY3QeTJHdzjtG+Yg=; b=GAUoWjahhGNiiDU5T4wlvGiVoZCKVb5dX8yTnEuTvYfuPu90SnX1Ff7Fa8E6lhVDVizbI02Fe35xO2379DKGf8rJT7fluX7z9bGN7yBaH32y4Zn1G4Rh+X8knDJdLa/8qGTJU5u2XKEmrdOGzylVMUeIEF1P17/ZhZ2V6soQKhq2FzNkAfhzNmdCMTWtQQ077i5GgedxOkEwlDD+pmCNKQxUggeBIqfPmBjGkcT3jDVT0o5FNKLhSxjy6DYHBT3i54dU4vIv7fZQlB5tPLbxFFlDfMCJQQCmNM7H0PwXv0A8rJtPbUj4R4Y+pi0zpdkpfRMD41RfjGaoHXd+DZRFYA== 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=BSwYgSCuGhydm7SW28wLKtBsLt0mY3QeTJHdzjtG+Yg=; b=NMMqPOgtd+KzSI+xGii7jOxTTC3SWz7rufc6/AfOHduYKGA1/OWSiBmRq8wAZQeK9kdBn8rviPX6dEMZ3Lw6+NtctHhfKFn2aUVy21lEC3lcySyTsP67JdIhYIA674ej/C4PW3ZEyAgJ7z7F7NbWDRDNPVTz7V88793svnQl9LCaXKiyyjJ541A/imaiWU4vGmPKA4snUul3bHQOQIepZvj8y2G50877nm++E/5SKbpwE7xOpzwxYY5uxYIKlBgmPU+l3UEqYxo7PjgviSeK1qGh+Qt1m6TslS80r2yYs+XfLfP2ShXzzX83koKQBdYzDwUXv4ZLYd+zu/lQqyDFLg== Authentication-Results: dkim=none (message not signed) header.d=none;dmarc=none action=none header.from=nvidia.com; Received: from BL0PR12MB4995.namprd12.prod.outlook.com (2603:10b6:208:1c7::23) by PH7PR12MB7379.namprd12.prod.outlook.com (2603:10b6:510:20e::10) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id 15.21.159.19; Tue, 7 Jul 2026 22:58:01 +0000 Received: from BL0PR12MB4995.namprd12.prod.outlook.com ([fe80::dde:9068:4b1a:53e2]) by BL0PR12MB4995.namprd12.prod.outlook.com ([fe80::dde:9068:4b1a:53e2%4]) with mapi id 15.21.0181.012; Tue, 7 Jul 2026 22:58:01 +0000 Date: Wed, 8 Jul 2026 08:57:51 +1000 From: Balbir Singh To: Lorenzo Stoakes Cc: Usama Arif , Andrew Morton , apopple@nvidia.com, baohua@kernel.org, baolin.wang@linux.alibaba.com, byungchul@sk.com, david@kernel.org, dev.jain@arm.com, gourry@gourry.net, jannh@google.com, joshua.hahnjy@gmail.com, lance.yang@linux.dev, liam@infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, matthew.brost@intel.com, npache@redhat.com, rakie.kim@sk.com, ryan.roberts@arm.com, vbabka@kernel.org, ying.huang@linux.alibaba.com, ziy@nvidia.com, shakeel.butt@linux.dev, hannes@cmpxchg.org Subject: Re: [PATCH 0/3] mm: handle device-private PMDs in walk callbacks Message-ID: References: <20260707135255.292870-1-usama.arif@linux.dev> Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-ClientProxiedBy: ME3P282CA0050.AUSP282.PROD.OUTLOOK.COM (2603:10c6:220:5::19) To CH2PR12MB5001.namprd12.prod.outlook.com (2603:10b6:610:61::18) 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: BL0PR12MB4995:EE_|PH7PR12MB7379:EE_ X-MS-Office365-Filtering-Correlation-Id: 2c5e56ba-24ed-4f4a-c576-08dedc7b2fa1 X-MS-Exchange-SenderADCheck: 1 X-MS-Exchange-AntiSpam-Relay: 0 X-Microsoft-Antispam: BCL:0;ARA:13230040|366016|23010399003|7416014|376014|1800799024|4143699003|6133799003|11063799006|56012099006|22082099003|18002099003; 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:BL0PR12MB4995.namprd12.prod.outlook.com;PTR:;CAT:NONE;SFS:(13230040)(366016)(23010399003)(7416014)(376014)(1800799024)(4143699003)(6133799003)(11063799006)(56012099006)(22082099003)(18002099003);DIR:OUT;SFP:1101; X-MS-Exchange-AntiSpam-MessageData-ChunkCount: 1 X-MS-Exchange-AntiSpam-MessageData-0: =?us-ascii?Q?DjiPi9oracUWG4Nh59D5AJjwHfRZraQiZQbeuIAu0Xj3RIwW9CT+yJM/T8Ix?= =?us-ascii?Q?4Ugy1tvcH5QmBP7g04A4WX/TsV3NlZretsDBZQLIXzO/5pEZo5TXbYTwvCfp?= =?us-ascii?Q?T03yMFrBS/WGmG61PhwXaTWHhbQN39ovAu+QYsN0uiypeDSfgMQKAC2tAd84?= =?us-ascii?Q?D6uTg6iWMCAPN6mpegw7cjWGGTSG5jWjN9rXlhulrlCh8rvRt2W36sah8kcB?= =?us-ascii?Q?h+QoMd1GHqItwmKe10UXAQ75Xy2id7EvTrEckch8kocjmuaQS9s4A1qBktT6?= =?us-ascii?Q?KgKcNyOSWZYXYMjuVqC9n8kHETPD/uHtws2rGZXFcRwjy7EBuYk4ERWYgPJc?= =?us-ascii?Q?cnTM1hXdYOwA1BQVA4drzwie8JWGHlc4f6pxMjtpt4H9dkBrLdExLeCkP4tI?= =?us-ascii?Q?ZfstbnPmOzQwkwEDd4+mTox7LGujtBlQBbaV3rhhsUqrHXH7E2n2FgPWwrYN?= =?us-ascii?Q?pXwKUEOyUmDYcR6vX6BAb7AEP3q2WbYpV/Ut8BzLMEhHyxQf/FadxaYDtt44?= =?us-ascii?Q?VyMgI9JGEhp3ePHNZ7S9LHr0miBeU7zbs5nE2d3nKiqQyaeQBMyuNcW/vlLF?= =?us-ascii?Q?BmrSzPTPeYeTiINDLjF1nnEIVWR7bMtj/mJxNktKfutV4jMd9xevn67NpQky?= =?us-ascii?Q?PdmI4C5+TMOrYGiPRwFDC/rfiOFLo9jDgB5+CeigaswY2Loy+p0mkYE/Gjjp?= =?us-ascii?Q?s709zvkVnU3/M3z4h/efJcODdHUCoun6g10APk2IKGNSMme6ONQ9N2Vh1xSJ?= =?us-ascii?Q?KWfS+MXrNd2ngl9hocN1oyje+XhREnNelPq9ygRmSCtbUwMGQhhltSw8SsOY?= =?us-ascii?Q?5GnnzOdelCcdBvjACHTD8qfdFvvTJv31tYdrsiLoY4I5Ylwid7KHJFlYQJkI?= =?us-ascii?Q?D5VPlM4ZiqQ/yrqSd5ftWpyyEsdiGyMziayjuTHXRiRPjzL5AIYHwWgcCFzM?= =?us-ascii?Q?DRFtvyHcjehHGffQDLEoIRTgIQj7OKCbsP+Ed9ie6bMmUoJRE6jdtNiHZQvG?= =?us-ascii?Q?YbMNQYAoJjumz4SI9i8JWA1SIlWYYoqwUTuLX0cuk8rLUONFNWXYMPvhiUOb?= =?us-ascii?Q?8JEe4eorT6ENrlTb9kxXOmcy5RfSWTt1RPdtycBPPvsod4YLFt1iDlDJzXvZ?= =?us-ascii?Q?/0D8E/ftbBbigZKKwuHEfaDZHniHJRCoglkLOI/xHCVQwF0eoZ29efc6UcYz?= =?us-ascii?Q?3M9mv4L2L6KGJnkBklACHytJnntT7NzSVgCvs0CiAMF9q0odwHKK7k2+fmAj?= =?us-ascii?Q?ST92Gf4/6fXpCl8hn8oIDxW5q5l9KQamE6p32S81uBWlyBHt5cRUOnAjkZkI?= =?us-ascii?Q?5uQYIhTMTFZsLyp7YHdppReOhWQhifScvVvks6MjjyBmq6XowCvO7zu3yOi/?= =?us-ascii?Q?JbjcEp8JVbA1fhdMXPtdHlF30d50qDhDvEFpUMX71WMUIUSEp3Z8GojbIyyH?= =?us-ascii?Q?VVoMqrOPSu3hdV1TTi+SjzGXKfip1LsKwEJeUsfbC87aMgdKcYujABM6ksmD?= =?us-ascii?Q?7OA1OmvRxqh7iD7qB83oi37bsi6HIowxRXyr9XBiwF17nxItQnpRGq1G1Lbh?= =?us-ascii?Q?7XptwBpoo5BWMYuZ0UhRphz3vFjFpZs+fn+ZdIUVP6A0s9NB0QiU9AMM9l3k?= =?us-ascii?Q?1VNP1Gw7cfAOOZXY5TfhwlO1ZK4ya1tRy7Qvz6Gw1nVllouhNvySb6BsTp0W?= =?us-ascii?Q?/1hMHhhyRAUMhSTMGlr+tURcbjM9WzhtCYVq3ivmvpZgVM1NeRDBgid8xtF/?= =?us-ascii?Q?x2ZWSw00kw=3D=3D?= X-OriginatorOrg: Nvidia.com X-MS-Exchange-CrossTenant-Network-Message-Id: 2c5e56ba-24ed-4f4a-c576-08dedc7b2fa1 X-MS-Exchange-CrossTenant-AuthSource: CH2PR12MB5001.namprd12.prod.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Internal X-MS-Exchange-CrossTenant-OriginalArrivalTime: 07 Jul 2026 22:58:01.4621 (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: 1xghmvO6uNNUgLoYkLzoT/ZXaNUUi8EYEPh2qhxxYqSY5enjpHT98VmvDLjYiKwobxmyD6CxPZTSmEtDnrP/Vw== X-MS-Exchange-Transport-CrossTenantHeadersStamped: PH7PR12MB7379 On Tue, Jul 07, 2026 at 03:01:56PM +0100, Lorenzo Stoakes wrote: > +cc Balbir > > Thanks for the series! > > I think Balbir should be cc'd no? > Thanks, my linux-mm monitoring has been largely skimming through the list. Explict cc's are always appreciated. > On Tue, Jul 07, 2026 at 06:45:06AM -0700, Usama Arif wrote: > > Since commit 368076f52ebe ("mm/huge_memory: add device-private THP support > > to PMD operations") a PMD may hold a device-private swap entry whenever > > an HMM-based GPU driver migrates an anonymous THP folio to device memory > > via migrate_vma_pages(). > > > > pmd_trans_huge_lock() succeeds for such PMDs (pmd_is_huge() returns true > > for any non-present, non-none huge PMD), so several MM walk callbacks > > that used to assume present THP or migration entry are now reachable with > > a device-private PMD. The results range from a VM_BUG_ON() firing on debug > > kernels, to an oops on a bogus vmemmap dereference, to silently isolating > > an unrelated live folio from LRU in the aliasing case. > > > > The first 2 fixes were reported as pre-existing issues by sashiko in my > > PMD swap entry series [1]. Hopefully sashiko won't point these out > > in the next PMD swap entry series :) > > Yeah I don't love these 'existing problem' reports (distracting from other work, > add workload, really it feels like that should be a passive reporting mode for > sashiko not arbitrarily added to other series), but sending it as a separate > series is indeed the right way :) > > These of course should never block an unrelated series. > > > > > [1] https://sashiko.dev/#/patchset/20260703173903.3789516-1-usama.arif%40linux.dev?part=6 > > Hmm we've had a whole host of issues with device-private PMDs recently. > > Balbir - would it be possible to audit all of the code paths and proactively see > if there's anything else that could hit problems here? > Let me run through this and audit them. My usage of device private PMD did not expose them, but I can see a bunch of reports in the link above > > > > Usama Arif (3): > > mm/mempolicy: skip device-private PMDs when queueing folios > > mm/madvise: skip device-private PMDs in cold and pageout walks > > mm/huge_memory: skip device-private PMDs in madvise_free_huge_pmd > > > > mm/huge_memory.c | 3 +++ > > mm/madvise.c | 3 +++ > > mm/mempolicy.c | 2 ++ > > 3 files changed, 8 insertions(+) > > > > -- > > 2.53.0-Meta > > > Thanks Lorenzo! Balbir