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 kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 930E4CA1015 for ; Thu, 4 Sep 2025 06:42:26 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id B7D498E000A; Thu, 4 Sep 2025 02:42:25 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id B2E088E0002; Thu, 4 Sep 2025 02:42:25 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 9F5B78E000A; Thu, 4 Sep 2025 02:42:25 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0010.hostedemail.com [216.40.44.10]) by kanga.kvack.org (Postfix) with ESMTP id 8AD7D8E0002 for ; Thu, 4 Sep 2025 02:42:25 -0400 (EDT) Received: from smtpin14.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay02.hostedemail.com (Postfix) with ESMTP id 4E8B613BCEB for ; Thu, 4 Sep 2025 06:42:25 +0000 (UTC) X-FDA: 83850623850.14.1B41487 Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by imf09.hostedemail.com (Postfix) with ESMTP id 0A6F7140006 for ; Thu, 4 Sep 2025 06:42:22 +0000 (UTC) Authentication-Results: imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=a+N2XwRs; spf=pass (imf09.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1756968143; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=KToomWKj9mg5gO92HiOMCLhfsKGdUXoXNpj3PWwnJys=; b=GWemWtMmthOVzN6p4ZGFbodBNmwf4nol7svyIp2BTTHgcekKYK8xi9pMyQut3JVLGNmAH7 gY7S5B8tzTrqR5rJAxOQD/Q5hTdSn7dcLWorr+UsfW7/C7sPxVDL+6WbSnGkSXGA5Ua1i7 R1hA4O3veT7vKFlytluHGz8DzLW+Cbk= ARC-Authentication-Results: i=1; imf09.hostedemail.com; dkim=pass header.d=redhat.com header.s=mimecast20190719 header.b=a+N2XwRs; spf=pass (imf09.hostedemail.com: domain of david@redhat.com designates 170.10.133.124 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (policy=quarantine) header.from=redhat.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1756968143; a=rsa-sha256; cv=none; b=B0yCAFoPWbSZJBwVaP95D4m1XrnJEDW/0AArm2eJ3DgOI6sXpbqmoBa0l0oO4brktqcUJL ugM0I4JrJnMQvm8fR0znAHGV0CxN58FxCKrBfEtlFfP/4xO5+sQobWrI85U+Gk7n/3D0rV iHmhRAljwqHxzueoW4v074NcmDp+it8= DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1756968142; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=KToomWKj9mg5gO92HiOMCLhfsKGdUXoXNpj3PWwnJys=; b=a+N2XwRsVY1jQOT10nRME0eYTnh6g1eK9MEB/vFifgJXRlAGrt0uqUvDGJFR06JvesM384 dBA3Dg6Dc3cQTmskahgvd6jnEpQdMSTO27MLw72OOPuPwBsf33DxPGwuytV8oRM218qNxx Kw7axC7klSDyWcukl79J3eEXJGhLGkY= Received: from mail-wm1-f72.google.com (mail-wm1-f72.google.com [209.85.128.72]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-166-fD_cFD2oNoePs4ETl18WoQ-1; Thu, 04 Sep 2025 02:42:21 -0400 X-MC-Unique: fD_cFD2oNoePs4ETl18WoQ-1 X-Mimecast-MFC-AGG-ID: fD_cFD2oNoePs4ETl18WoQ_1756968140 Received: by mail-wm1-f72.google.com with SMTP id 5b1f17b1804b1-45b9912a07dso3298575e9.3 for ; Wed, 03 Sep 2025 23:42:20 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1756968140; x=1757572940; h=content-transfer-encoding:in-reply-to:autocrypt:content-language :from:references:cc:to:subject:user-agent:mime-version:date :message-id:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=KToomWKj9mg5gO92HiOMCLhfsKGdUXoXNpj3PWwnJys=; b=QpgyrpcmQ6VY74eAQ8Kvy5iRJQUbZyKBxNoUBWz3sFdzwBuV+bsG2wuEsMR48CxF9+ zEQLfCTa7S3OlBIzRZmfkhBu+ttEl5azvAl/KUzA69n0hs2WT5L9LmnQfOIam31t5luy IwFKTSGXZbRmajjDOVhcUgFszerr/vKEy3+3Upt1QPCGMs6snUGBFxggN+RylPKmkMQC 4zMObhJGKP/jybNc9XQlO0UoGZ58AXdEuNVHUM4W+9UYHe70+YctWph75ytsDiqqtZvG XiurFV9xCaL/01fk/vJxIIO4xZIr8uMq3Cvfx5PLq/XMxD46yHYjNxmPLmVp4xPvBCwz JJgA== X-Gm-Message-State: AOJu0YyzKgzJ+kGpxrbez9oAjs75rjrkxeQeSEbIK4FTuLlZAGJsbAyh HIEgmbkODI7O+WQF4zqlTkwbf6XJtnvmKXdSKJzPoz+VA4kMqEfk9CB2REgCECVtjKhtNh2jGwF 71+wc0vlpIvZ++DZ5bIrkee2A8f5v/+i9quuJlS2S8ZGbkpOvMd2a X-Gm-Gg: ASbGncvyjdQ3J9F7pVVxvu+YdYWWVkZ0DQaL8f4AzBwxkh8+ffDkUeP3OkaEk2+VILo MkKQlJYBJj8tDELqqFGFj+1phvO/RZFdWSeQl9YcavxV5q5xQRg/au/azq1C4o+8t9SXm181Iao L+aQCcsu7GphbxGFl7zz2V6oMx0SUwZBDbDiH0JErSvp+5/okCrJruuPhyZ3UmwzW8l75YpjuUa hG6Kn9O6DfK34mB4YLLIprRWslyHrQmYUWLiITYBlailpZ2vao/8WSjrGM2vjRULVTx/1otMbgs VxM91Tn/ZHaMEE8VQQYAjlCtDiGL1MAE3nf3Ew4SA3aKB6lXzQbeWmc5kal9drH2vF3Gm2ON+dB ked5eyPpz4H8AOoqvasoe5h1n1zdR/vfDaZQeJp5p8fLWTzaKAUwqV6I3qHieINrd X-Received: by 2002:a05:600c:3f0a:b0:45b:8703:741b with SMTP id 5b1f17b1804b1-45b870374demr140352305e9.32.1756968139750; Wed, 03 Sep 2025 23:42:19 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEDY+KZJxIteq5+5ELGWzXe1Yo4ms4pskv7HMB5FhUoffpW2kCYxWLFHE3oFlp3rlHbnFi9+g== X-Received: by 2002:a05:600c:3f0a:b0:45b:8703:741b with SMTP id 5b1f17b1804b1-45b870374demr140351995e9.32.1756968139315; Wed, 03 Sep 2025 23:42:19 -0700 (PDT) Received: from ?IPV6:2003:d8:2f25:1e00:ce4c:be3:97b3:6587? (p200300d82f251e00ce4c0be397b36587.dip0.t-ipconnect.de. [2003:d8:2f25:1e00:ce4c:be3:97b3:6587]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-45c6faad9cfsm80007195e9.0.2025.09.03.23.42.17 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 03 Sep 2025 23:42:18 -0700 (PDT) Message-ID: <239ecae6-2fc0-43be-bc63-08f52b39a524@redhat.com> Date: Thu, 4 Sep 2025 08:42:17 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm: Fix kernel stack tagging for certain configs To: Matthew Wilcox , "Vishal Moola (Oracle)" Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Andrew Morton , Ingo Molnar , Peter Zijlstra , Juri Lelli , Vincent Guittot , Kees Cook , kernel test robot , Dan Carpenter References: <20250902175903.1124555-1-vishal.moola@gmail.com> From: David Hildenbrand Autocrypt: addr=david@redhat.com; keydata= xsFNBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzSREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZoEEwEIAEQCGwMCF4ACGQEFCwkIBwICIgIG FQoJCAsCBBYCAwECHgcWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaJzangUJJlgIpAAKCRBN 3hD3AP+DWhAxD/9wcL0A+2rtaAmutaKTfxhTP0b4AAp1r/eLxjrbfbCCmh4pqzBhmSX/4z11 opn2KqcOsueRF1t2ENLOWzQu3Roiny2HOU7DajqB4dm1BVMaXQya5ae2ghzlJN9SIoopTWlR 0Af3hPj5E2PYvQhlcqeoehKlBo9rROJv/rjmr2x0yOM8qeTroH/ZzNlCtJ56AsE6Tvl+r7cW 3x7/Jq5WvWeudKrhFh7/yQ7eRvHCjd9bBrZTlgAfiHmX9AnCCPRPpNGNedV9Yty2Jnxhfmbv Pw37LA/jef8zlCDyUh2KCU1xVEOWqg15o1RtTyGV1nXV2O/mfuQJud5vIgzBvHhypc3p6VZJ lEf8YmT+Ol5P7SfCs5/uGdWUYQEMqOlg6w9R4Pe8d+mk8KGvfE9/zTwGg0nRgKqlQXrWRERv cuEwQbridlPAoQHrFWtwpgYMXx2TaZ3sihcIPo9uU5eBs0rf4mOERY75SK+Ekayv2ucTfjxr Kf014py2aoRJHuvy85ee/zIyLmve5hngZTTe3Wg3TInT9UTFzTPhItam6dZ1xqdTGHZYGU0O otRHcwLGt470grdiob6PfVTXoHlBvkWRadMhSuG4RORCDpq89vu5QralFNIf3EysNohoFy2A LYg2/D53xbU/aa4DDzBb5b1Rkg/udO1gZocVQWrDh6I2K3+cCs7BTQRVy5+RARAA59fefSDR 9nMGCb9LbMX+TFAoIQo/wgP5XPyzLYakO+94GrgfZjfhdaxPXMsl2+o8jhp/hlIzG56taNdt VZtPp3ih1AgbR8rHgXw1xwOpuAd5lE1qNd54ndHuADO9a9A0vPimIes78Hi1/yy+ZEEvRkHk /kDa6F3AtTc1m4rbbOk2fiKzzsE9YXweFjQvl9p+AMw6qd/iC4lUk9g0+FQXNdRs+o4o6Qvy iOQJfGQ4UcBuOy1IrkJrd8qq5jet1fcM2j4QvsW8CLDWZS1L7kZ5gT5EycMKxUWb8LuRjxzZ 3QY1aQH2kkzn6acigU3HLtgFyV1gBNV44ehjgvJpRY2cC8VhanTx0dZ9mj1YKIky5N+C0f21 zvntBqcxV0+3p8MrxRRcgEtDZNav+xAoT3G0W4SahAaUTWXpsZoOecwtxi74CyneQNPTDjNg azHmvpdBVEfj7k3p4dmJp5i0U66Onmf6mMFpArvBRSMOKU9DlAzMi4IvhiNWjKVaIE2Se9BY FdKVAJaZq85P2y20ZBd08ILnKcj7XKZkLU5FkoA0udEBvQ0f9QLNyyy3DZMCQWcwRuj1m73D sq8DEFBdZ5eEkj1dCyx+t/ga6x2rHyc8Sl86oK1tvAkwBNsfKou3v+jP/l14a7DGBvrmlYjO 59o3t6inu6H7pt7OL6u6BQj7DoMAEQEAAcLBfAQYAQgAJgIbDBYhBBvZyq1zXEw6Rg38yk3e EPcA/4NaBQJonNqrBQkmWAihAAoJEE3eEPcA/4NaKtMQALAJ8PzprBEXbXcEXwDKQu+P/vts IfUb1UNMfMV76BicGa5NCZnJNQASDP/+bFg6O3gx5NbhHHPeaWz/VxlOmYHokHodOvtL0WCC 8A5PEP8tOk6029Z+J+xUcMrJClNVFpzVvOpb1lCbhjwAV465Hy+NUSbbUiRxdzNQtLtgZzOV Zw7jxUCs4UUZLQTCuBpFgb15bBxYZ/BL9MbzxPxvfUQIPbnzQMcqtpUs21CMK2PdfCh5c4gS sDci6D5/ZIBw94UQWmGpM/O1ilGXde2ZzzGYl64glmccD8e87OnEgKnH3FbnJnT4iJchtSvx yJNi1+t0+qDti4m88+/9IuPqCKb6Stl+s2dnLtJNrjXBGJtsQG/sRpqsJz5x1/2nPJSRMsx9 5YfqbdrJSOFXDzZ8/r82HgQEtUvlSXNaXCa95ez0UkOG7+bDm2b3s0XahBQeLVCH0mw3RAQg r7xDAYKIrAwfHHmMTnBQDPJwVqxJjVNr7yBic4yfzVWGCGNE4DnOW0vcIeoyhy9vnIa3w1uZ 3iyY2Nsd7JxfKu1PRhCGwXzRw5TlfEsoRI7V9A8isUCoqE2Dzh3FvYHVeX4Us+bRL/oqareJ CIFqgYMyvHj7Q06kTKmauOe4Nf0l0qEkIuIzfoLJ3qr5UyXc2hLtWyT9Ir+lYlX9efqh7mOY qIws/H2t In-Reply-To: X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: JbV-4TxZ55lHxDQXtW0VL9tk0G3JQT94zaAUF2gT8d0_1756968140 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam02 X-Rspamd-Queue-Id: 0A6F7140006 X-Stat-Signature: f64k3w59tppj68xpimc7pfdut3x74hm5 X-Rspam-User: X-HE-Tag: 1756968142-312258 X-HE-Meta: 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 ihgSBquc NjI9JIWybKuOUl3GCDcKFXrXxl4+t+1oGmeZgCZCaP34XlC9xXdobsadOQJe2il5wtUGbnwvoWT4x42IAWsDIYw07TkGOdy56SXOKqZlaxZoGENR2xg4IDqn3OxjY+e2xI810622fgktyucskYuVGLkpf7BnI22ijAipMRVirCHoRQn9J/tf0gQUUMrVfl3yPmdUOrxESMsuekfVtzSfSsKWGQXw/JKkebbdqWuECcmNn9adoSNrJytRi7ypcAXt7nw2TXiqX5PP0372gSdO9WLg3p+ZtJz4e5O8b/A3SQmnH9jCFVNY/ZigfRVpUatASq2CZ6j8hC6feDZzHWfiV9i/jzwlFRjDdrkPPCeYOazfAghVAAT+ep97cSvjXboDJR29LSvM3cPUVlL3KzoR5/0THrhGXfDEglrDmpxmvRdiMELo6vs9pUrmrEXLQBXLvRwPBmyYupXfSMyRDhUb8FL9wow== X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 02.09.25 21:30, Matthew Wilcox wrote: > On Tue, Sep 02, 2025 at 10:59:03AM -0700, Vishal Moola (Oracle) wrote: >> There are 3 cases where kernel pages are allocated for kernel stacks: >> CONFIG_VMAP_STACK, THREAD_SIZE >= PAGE_SIZE, THREAD_SIZE < PAGE_SIZE. >> These cases use vmalloc(), alloc_pages() and kmem_cache_alloc() >> respectively. > > I missed that the third case existed ... > >> In the first 2 cases, THREAD_SIZE / PAGE_SIZE will always be greater >> than 0, and pages are tagged as expected. In the third case, >> THREAD_SIZE / PAGE_SIZE evaluates to 0 and doesn't tag any pages at all. >> This meant that in those configs, the stack tagging was a no-op, and led >> to smatch build warnings. > > I didn't see those smatch warnings. Were they cc'd to the mailing list? > >> We definitely have at least 1 page we want tagged at this point, so fix >> it by using a do {} while loop instead of a for loop. > > We can't do this. Pages can only have one type at a time. Since > they're allocated from slab, they have PGTY_slab. This will lead to > a warning at runtime: > > VM_BUG_ON_PAGE(data_race(page->page_type) != UINT_MAX, page); \ > > But for our purposes (trying to figure out how fragmented the vmap > stack is making the memmap), we don't need to do this accounting. > These pages are already being allocated from slab, and slab allocates > naturally aligned, so we can skip all of this for these configurations. IIUC what you mean, I am not a fan of having PGTY_stack being properly set or not based on a kernel config. I much rather prefer this being done cleanly for all cases, or not at all (OOT for research/debugging purposes). -- Cheers David / dhildenb