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 1047EFE521D for ; Fri, 24 Apr 2026 12:29:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 417BC6B0005; Fri, 24 Apr 2026 08:29:57 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 3EFB36B009B; Fri, 24 Apr 2026 08:29:57 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 305006B009D; Fri, 24 Apr 2026 08:29:57 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 20B716B0005 for ; Fri, 24 Apr 2026 08:29:57 -0400 (EDT) Received: from smtpin20.hostedemail.com (lb01b-stub [10.200.18.250]) by unirelay08.hostedemail.com (Postfix) with ESMTP id A83E414018C for ; Fri, 24 Apr 2026 12:29:56 +0000 (UTC) X-FDA: 84693381192.20.E92D993 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf14.hostedemail.com (Postfix) with ESMTP id E4232100012 for ; Fri, 24 Apr 2026 12:29:54 +0000 (UTC) Authentication-Results: imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=GMP7indr; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1777033794; 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=Y6fNq3bLLblcuhX/ezeW8fniX00qVWvolSa35e9m/Yk=; b=UllMpLUCBpu5Lg72BZzqCgVkg4fdhEYhxl9dM8PsUc935dFyxZkcEkhVs0WrdwiM+rYFT3 eafqnIh8SN3Znh8NJ3lqH+HGHrH6MVhOMzzgplfycvsavjbbc7bnywaoX9CnIhQwcvSRit V2cOKxe4rAZGGwjzoL19S8RO2QkhNs0= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1777033794; a=rsa-sha256; cv=none; b=BXUnEdl3/BTvt7DEXVxc2L0oysaiHAfT1FceAybZEm4970meXu8oiYAeWL3dxwOY2uIiAu FpPIrjJwircm0Gsu2dl/ENitHzUjopOA3oLIJ9h0V4hiYIDP5CeoAcV2Y+0t1pHhfKxmtW AuefHmfsmHDHo5YvytYStehMsDGHNBA= ARC-Authentication-Results: i=1; imf14.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=GMP7indr; spf=pass (imf14.hostedemail.com: domain of david@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=david@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id 56B54600AE; Fri, 24 Apr 2026 12:29:54 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0B83CC19425; Fri, 24 Apr 2026 12:29:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1777033794; bh=xuaMXZZQHTCLWOn+RiAaPNIAvlQmSERJSFvFOzPMvlQ=; h=Date:Subject:To:Cc:References:From:In-Reply-To:From; b=GMP7indrU77W+r7c7BQJDzWNuwDS7Svmqq4sBy8ieEmzMi5uh16P8Rt0Ax/7vqTtK EysXMjjYYx97m95htM9KUAIBqoEA4FnNjQ1SLN9OSYOLt4jNMOVVEys5amHoFf/fk/ VP6Jy+syyvQRaaywUWg3ZKrlQEkBtkJspRuYV+Yhk7uPBarKelHvil1d2gi4OlEFWv PNEOKfwuDJilZUMftcpZzzYbySgTxz2yji+/nfw5QVIaehjH08DX57L/RTbeI8HwEr +NsGZwc45SFj0tU20g2P4zKDpFKeDncDpSvfu8ccNCldiY3Ix+Wz8vsvDyzCVqvD/X 4fe3mbYbLRS7A== Message-ID: <4b30e014-2746-47d9-a122-554572271d9b@kernel.org> Date: Fri, 24 Apr 2026 14:29:49 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/5] mm/sparse-vmemmap: provide generic vmemmap_set_pmd() and vmemmap_check_pmd() To: Mike Rapoport , Muchun Song Cc: Muchun Song , Andrew Morton , linux-mm@kvack.org, Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Suren Baghdasaryan , Michal Hocko , linux-kernel@vger.kernel.org References: <20260404122105.3989557-1-songmuchun@bytedance.com> <20260404122105.3989557-2-songmuchun@bytedance.com> From: "David Hildenbrand (Arm)" Content-Language: en-US Autocrypt: addr=david@kernel.org; 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 B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABzS5EYXZpZCBIaWxk ZW5icmFuZCAoQ3VycmVudCkgPGRhdmlkQGtlcm5lbC5vcmc+wsGQBBMBCAA6AhsDBQkmWAik AgsJBBUKCQgCFgICHgUCF4AWIQQb2cqtc1xMOkYN/MpN3hD3AP+DWgUCaYJt/AIZAQAKCRBN 3hD3AP+DWriiD/9BLGEKG+N8L2AXhikJg6YmXom9ytRwPqDgpHpVg2xdhopoWdMRXjzOrIKD g4LSnFaKneQD0hZhoArEeamG5tyo32xoRsPwkbpIzL0OKSZ8G6mVbFGpjmyDLQCAxteXCLXz ZI0VbsuJKelYnKcXWOIndOrNRvE5eoOfTt2XfBnAapxMYY2IsV+qaUXlO63GgfIOg8RBaj7x 3NxkI3rV0SHhI4GU9K6jCvGghxeS1QX6L/XI9mfAYaIwGy5B68kF26piAVYv/QZDEVIpo3t7 /fjSpxKT8plJH6rhhR0epy8dWRHk3qT5tk2P85twasdloWtkMZ7FsCJRKWscm1BLpsDn6EQ4 jeMHECiY9kGKKi8dQpv3FRyo2QApZ49NNDbwcR0ZndK0XFo15iH708H5Qja/8TuXCwnPWAcJ DQoNIDFyaxe26Rx3ZwUkRALa3iPcVjE0//TrQ4KnFf+lMBSrS33xDDBfevW9+Dk6IISmDH1R HFq2jpkN+FX/PE8eVhV68B2DsAPZ5rUwyCKUXPTJ/irrCCmAAb5Jpv11S7hUSpqtM/6oVESC 3z/7CzrVtRODzLtNgV4r5EI+wAv/3PgJLlMwgJM90Fb3CB2IgbxhjvmB1WNdvXACVydx55V7 LPPKodSTF29rlnQAf9HLgCphuuSrrPn5VQDaYZl4N/7zc2wcWM7BTQRVy5+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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: E4232100012 X-Rspamd-Server: rspam07 X-Stat-Signature: d5un9c55xj31yg9grrx3qr1emdzzzinj X-Rspam-User: X-HE-Tag: 1777033794-918089 X-HE-Meta: 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 y1CFz6aY tazFx8egicAEOQ/juxZZlVZFK4V2D2oxxN0aPAS3B43kR/nSscG/baYpCbSZepK/kc2zE8a9+0yWbvSnDMGdo5aZ0om3MM404xbfh06IWqD7OgCUKUgLaxbVAMcLRWbuo8LLDOrzoUNXZwutQrYtw/IitTTjQSs9+mqUamLdW3ef3+/Bkc9q1yeEPJeqD2lEpIw3R3Q0nuu1G53WsiS4Ly4NdyjfqoR1BjJiy0is0rrff0rAzPsISA+e/H7AX1+ooqEaM+70YhxPi1YrhWmPhnx38gR6tNtpi5AN3h43PJuynB4opqcwYHInaCw== Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 4/9/26 12:44, Mike Rapoport wrote: > On Sun, Apr 05, 2026 at 10:07:36PM +0800, Muchun Song wrote: >>> >>> Do we have to crash the kernel here? >>> Wouldn't be better to make vmemmap_set_pmd() return error and make >>> vmemmap_populate_hugepages() fall back to base pages in case >>> vmemmap_set_pmd() errored? >> >> Hi Mike, >> >> Thanks for the review. Let me explain my original thought process here. >> >> My assumption was that pmd_set_huge() for the kernel virtual address space >> should rarely, if ever, fail in this context. Furthermore, if we look at the >> architectures this patch replaces (e.g., arm64 and riscv), they are either >> ignoring the return value of pmd_set_huge() entirely or lacking any graceful >> fallback mechanism anyway. >> >> So, to keep the initial generic implementation as simple as possible, I used >> BUG_ON() as a strict assertion. > > Fair enough, let's just make it VM_BUG_ON(). VM_WARN_ON_* please. -- Cheers, David