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 35FE0C5B543 for ; Tue, 10 Jun 2025 16:08:23 +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:Content-Transfer-Encoding: Content-Type:In-Reply-To:References:Cc:To:From:Subject:MIME-Version:Date: Message-ID:Reply-To:Content-ID:Content-Description:Resent-Date:Resent-From: Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Owner; bh=UOUtyIivh13PUqsEgCb8n92bCG7VplbjadncEisJiSE=; b=vkyg/EFnGeuMTJ98QNG2gILY3O gv7O9b6d8urADlLaZKCtdu0plMABlA0zCOc/0Iy2E7JHUnwhfi6L8HROD80/UQzM034tEkQKoCo6h YQtbEFb/MfCIVlp55iG6R7b7mSrXkZjT8AUe4Y4PM7ySeby2UEL6eqJutlFbZSOhg7ERDrLu9sPoe WV9aA9yfYeR3jy4ndDHT/QBfYCIuhKhj6LfPnTHS9VkeQzXMk9G4Y4tpLb53yn9zSwGWao1rVifz9 W5fLahh/9zQAOFGG/9pTdESjSWiFfzS6xqOZIt8f0VZP4hsGxqPNKLmPmRiRiAn1bitRxA4sbHJ+y QKmKcDxw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.98.2 #2 (Red Hat Linux)) id 1uP1WL-00000007QLG-0mzM; Tue, 10 Jun 2025 16:08:17 +0000 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by bombadil.infradead.org with esmtps (Exim 4.98.2 #2 (Red Hat Linux)) id 1uOyzK-00000006xbz-2xdh for linux-arm-kernel@lists.infradead.org; Tue, 10 Jun 2025 13:26:03 +0000 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1749561961; 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=UOUtyIivh13PUqsEgCb8n92bCG7VplbjadncEisJiSE=; b=PtEVJ1Ko9yM4OrUHVi7fvhvKMAO1/WgwMcItOpxzEg3oM7FKBO4gDf7vrZvBvSbzOkmJjD chwLQoJL4azkrzNRCmn21ELPvEzHJPOeJyEFFpo9j80F83iu1b6Tv8wmzoIs9ug2FLbMqY knTeP4uoqh67a9oBu8jlUh4j+WxSc+s= Received: from mail-wm1-f70.google.com (mail-wm1-f70.google.com [209.85.128.70]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-632-RTGBwK6SO2WvbJZSnSjxLQ-1; Tue, 10 Jun 2025 09:25:58 -0400 X-MC-Unique: RTGBwK6SO2WvbJZSnSjxLQ-1 X-Mimecast-MFC-AGG-ID: RTGBwK6SO2WvbJZSnSjxLQ_1749561957 Received: by mail-wm1-f70.google.com with SMTP id 5b1f17b1804b1-453080e4741so21755265e9.0 for ; Tue, 10 Jun 2025 06:25:58 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1749561957; x=1750166757; h=content-transfer-encoding:in-reply-to:organization:autocrypt :content-language:references:cc:to:from:subject:user-agent :mime-version:date:message-id:x-gm-message-state:from:to:cc:subject :date:message-id:reply-to; bh=UOUtyIivh13PUqsEgCb8n92bCG7VplbjadncEisJiSE=; b=klqVYkbE2qkWXaSm9vvvPqwxgoi9cF934JKIqxL+tJ2mjAXXxePt6f2tZ8Q1FElfRI kQpAUyyJg6jUyKtukLaPy+8iU8T+XLyRrFVqJzsR8pqvxo/2C7Ws8NFO6fyz4hulRyQR lOW/NTh0rvAcv0sJ7LRlfdUuBJmn87+z5WOOPqLdrqc6tG34ho3toP0YBaNZysB4994j aYL8K5X0YcEHMX6W2v0WEpWu307SU/Xuz1KWms11K256Z7rOq2Ss7dvGLiSCYv9cjubS vbyzm5l3nd/7MO1pVnjaCGIYGaFC4bamaVttASZ8m1jeXBSXUbhOxC54UaBNHJ1PVrAC xDew== X-Forwarded-Encrypted: i=1; AJvYcCVWsfoKjXUcGjr1/IsyPNbrsHxz07l6AzHgWxXUpVYSP8byYLghyRti4lq71TKqDegqaqbhu+VA6TtixuzYJ4sF@lists.infradead.org X-Gm-Message-State: AOJu0YxEI0cUSXaZdlQhGb7EkttpjTaFVL8R5d5KxSgrghWwgQsMAoPy 1XIFzubUSyiurqJ552+PhyYzndgHx6E/sl1rZG7nfPySxwufEc9WRxQ+ONg/IF8DzUZukpH/WOG YD6K4CCCEq8ZNKDeWvcmcfYZAo2Y4gHyXo+XSFbWUP4LaXy4VRzeVWxGx0FtW4mrckDrmmHoLEO xj X-Gm-Gg: ASbGncuLs6bO/koSqxOc0uRILP66mJjiFuPIC0ecGZCo2LU8FaXTYMhe498CHnqrb+N yQcyk/3Sb5OotwoUQAELpVyn3aIdkOQSuwiQmsQC/osJ2cD4U/ZFOJEZkIyP2exjplaJdb8h1eU fY0hz/L5YXub/njS31G61H4p7Wq8MEObcJm/2aKJxhcaBSAnf9GJwOg81Bm60VmfqCEKPF5jhUk fC0mbQgeoNqs0up+qIa9l+DukqUyR73c5sBhIuZc4/r10RZY++WNM7f+j7hgcH0mxSRW1/q98Am 6iiTTf4YRl//vCXCDw2wF3vC6a4KdczEUGVy+E7AZa9+hKAPxJBccTs= X-Received: by 2002:a05:6000:288c:b0:3a4:db49:94aa with SMTP id ffacd0b85a97d-3a531ab5272mr15309114f8f.21.1749561957106; Tue, 10 Jun 2025 06:25:57 -0700 (PDT) X-Google-Smtp-Source: AGHT+IF/7kPqZZ/+Y3az8v7akKRzwFHXYkHgzSWQ8MYzhrEcJkdseIufvqvlRRJq+UmTakgX+RwCpQ== X-Received: by 2002:a05:6000:288c:b0:3a4:db49:94aa with SMTP id ffacd0b85a97d-3a531ab5272mr15309070f8f.21.1749561956651; Tue, 10 Jun 2025 06:25:56 -0700 (PDT) Received: from ?IPV6:2a09:80c0:192:0:5dac:bf3d:c41:c3e7? ([2a09:80c0:192:0:5dac:bf3d:c41:c3e7]) by smtp.gmail.com with ESMTPSA id ffacd0b85a97d-3a5323bee86sm12051355f8f.43.2025.06.10.06.25.55 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 10 Jun 2025 06:25:56 -0700 (PDT) Message-ID: Date: Tue, 10 Jun 2025 15:25:55 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/2] mm: Allow lockless kernel pagetable walking From: David Hildenbrand To: Lorenzo Stoakes , Dev Jain Cc: akpm@linux-foundation.org, catalin.marinas@arm.com, will@kernel.org, Liam.Howlett@oracle.com, vbabka@suse.cz, rppt@kernel.org, surenb@google.com, mhocko@suse.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, suzuki.poulose@arm.com, steven.price@arm.com, gshan@redhat.com, linux-arm-kernel@lists.infradead.org, yang@os.amperecomputing.com, ryan.roberts@arm.com, anshuman.khandual@arm.com References: <20250610114401.7097-1-dev.jain@arm.com> <20250610114401.7097-2-dev.jain@arm.com> <970e1b84-7f47-4a51-ad99-4df9026b8f7d@redhat.com> 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 ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT7CwZgEEwEIAEICGwMGCwkIBwMCBhUIAgkKCwQW AgMBAh4BAheAAhkBFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl8Ox4kFCRKpKXgACgkQTd4Q 9wD/g1oHcA//a6Tj7SBNjFNM1iNhWUo1lxAja0lpSodSnB2g4FCZ4R61SBR4l/psBL73xktp rDHrx4aSpwkRP6Epu6mLvhlfjmkRG4OynJ5HG1gfv7RJJfnUdUM1z5kdS8JBrOhMJS2c/gPf wv1TGRq2XdMPnfY2o0CxRqpcLkx4vBODvJGl2mQyJF/gPepdDfcT8/PY9BJ7FL6Hrq1gnAo4 3Iv9qV0JiT2wmZciNyYQhmA1V6dyTRiQ4YAc31zOo2IM+xisPzeSHgw3ONY/XhYvfZ9r7W1l pNQdc2G+o4Di9NPFHQQhDw3YTRR1opJaTlRDzxYxzU6ZnUUBghxt9cwUWTpfCktkMZiPSDGd KgQBjnweV2jw9UOTxjb4LXqDjmSNkjDdQUOU69jGMUXgihvo4zhYcMX8F5gWdRtMR7DzW/YE BgVcyxNkMIXoY1aYj6npHYiNQesQlqjU6azjbH70/SXKM5tNRplgW8TNprMDuntdvV9wNkFs 9TyM02V5aWxFfI42+aivc4KEw69SE9KXwC7FSf5wXzuTot97N9Phj/Z3+jx443jo2NR34XgF 89cct7wJMjOF7bBefo0fPPZQuIma0Zym71cP61OP/i11ahNye6HGKfxGCOcs5wW9kRQEk8P9 M/k2wt3mt/fCQnuP/mWutNPt95w9wSsUyATLmtNrwccz63XOwU0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAHCwXwEGAEIACYCGwwWIQQb2cqtc1xMOkYN/MpN3hD3 AP+DWgUCXw7HsgUJEqkpoQAKCRBN3hD3AP+DWrrpD/4qS3dyVRxDcDHIlmguXjC1Q5tZTwNB boaBTPHSy/Nksu0eY7x6HfQJ3xajVH32Ms6t1trDQmPx2iP5+7iDsb7OKAb5eOS8h+BEBDeq 3ecsQDv0fFJOA9ag5O3LLNk+3x3q7e0uo06XMaY7UHS341ozXUUI7wC7iKfoUTv03iO9El5f XpNMx/YrIMduZ2+nd9Di7o5+KIwlb2mAB9sTNHdMrXesX8eBL6T9b+MZJk+mZuPxKNVfEQMQ a5SxUEADIPQTPNvBewdeI80yeOCrN+Zzwy/Mrx9EPeu59Y5vSJOx/z6OUImD/GhX7Xvkt3kq Er5KTrJz3++B6SH9pum9PuoE/k+nntJkNMmQpR4MCBaV/J9gIOPGodDKnjdng+mXliF3Ptu6 3oxc2RCyGzTlxyMwuc2U5Q7KtUNTdDe8T0uE+9b8BLMVQDDfJjqY0VVqSUwImzTDLX9S4g/8 kC4HRcclk8hpyhY2jKGluZO0awwTIMgVEzmTyBphDg/Gx7dZU1Xf8HFuE+UZ5UDHDTnwgv7E th6RC9+WrhDNspZ9fJjKWRbveQgUFCpe1sa77LAw+XFrKmBHXp9ZVIe90RMe2tRL06BGiRZr jPrnvUsUUsjRoRNJjKKA/REq+sAnhkNPPZ/NNMjaZ5b8Tovi8C0tmxiCHaQYqj7G2rgnT0kt WNyWQQ== Organization: Red Hat In-Reply-To: <970e1b84-7f47-4a51-ad99-4df9026b8f7d@redhat.com> X-Mimecast-Spam-Score: 0 X-Mimecast-MFC-PROC-ID: R49vSM1TISNCBU-wNvCQlFcKnxe5lCwlXVNG8J95Qe4_1749561957 X-Mimecast-Originator: redhat.com Content-Language: en-US Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20250610_062602_817423_B125D821 X-CRM114-Status: GOOD ( 12.58 ) 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 On 10.06.25 15:24, David Hildenbrand wrote: > On 10.06.25 14:07, Lorenzo Stoakes wrote: >> OK so I think the best solution here is to just update check_ops_valid(), which >> was kind of sucky anyway (we check everywhere but walk_page_range_mm() to >> enforce the install pte thing). >> >> Let's do something like: >> >> #define OPS_MAY_INSTALL_PTE (1<<0) >> #define OPS_MAY_AVOID_LOCK (1<<1) >> >> and update check_ops_valid() to take a flags or maybe 'capabilities' field. >> >> Then check based on this e.g.: >> >> if (ops->install_pte && !(capabilities & OPS_MAY_INSTALL_PTE)) >> return false; >> >> if (ops->walk_lock == PGWALK_NOLOCK && !(capabilities & OPS_MAY_AVOID_LOCK)) >> return false; >> > > Hm. I mean, we really only want to allow this lockless check for > walk_kernel_page_table_range(), right? > > Having a walk_kernel_page_table_range_lockeless() might (or might not) > be better, to really only special-case this specific path. Note that I am also not quite happy bout that function name, but I think we should add a proper interface that documents clearly when it is even okay to call that function ... -- Cheers, David / dhildenb