From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-alma10-1.taild15c8.ts.net [100.103.45.18]) (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 32E2734D3B9; Mon, 29 Jun 2026 17:43:58 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=100.103.45.18 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782755039; cv=none; b=FAA0t3YGfMyD9C/XgHCTEDfljLDmTmczPoBL/4CCfdRd0HhkObZECYIwlUfEg4w9vJjNbFN3al2mi5NgQurT/qXwZ6IALXyroUrX2+asruwMAtDKflBKZQLmArXTf/+7iElqgkWozolbL28vCKiOA1TKYUlLPc+ckz96cNgteVs= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1782755039; c=relaxed/simple; bh=8L9FGavC4ul9iL2IyJlhwaB8NzuFv78Rma1Bq2wVC4g=; h=Message-ID:Date:MIME-Version:Subject:To:Cc:References:From: In-Reply-To:Content-Type; b=CK4yNNHehvytNvozuTLha/y01p7710WPGDQR22mbk/aIc6rkLDpDaAASN7E0zAhrpheRmqcSSWOLV0/Ym6OuhogllAmPbiPdL2kIO1TBbKNgfREoBZ6oHGYTO/ZZJAJDZirEOmHslDN+KTnct3ClZOTA4GP6ety3dCiCcM+ksCk= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=FMBCmM6u; arc=none smtp.client-ip=100.103.45.18 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="FMBCmM6u" Received: by smtp.kernel.org (Postfix) with ESMTPSA id A2A651F000E9; Mon, 29 Jun 2026 17:43:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1782755038; bh=sNPWUj0b3dpxJFm9DmiWQoTjCiuvhdzLK8xC9ADnE8o=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=FMBCmM6uX9VREwWikdZd8AjqjhA0cn8zckZezxCiaDRwpSVAuFWVUsl7qw03ZO1Hq O40u+9Ah0zciqqs3VgdDdNVUFsHXteukIHLzAm0/rSDQzzzAJ1EfJEalXtLOZYDTe4 TsRC/hFucqYfARZ4BGTVaoMkXlPVDT3WIBdsq4bB8ecDMYMcBFzPHuUS7vSTgQyV82 e3e7QmolFwS1AZUMzBVQjbX4C+K4Mgv3wroJoKMpxvEfE1BUXOBzzl5w0F4vcXxE8Q GDdkUQxFMLe1h1Pl3KtE1y3UtvsCeWMliEQrBJxAzME36Iz+vio0+BTH5F0NwWOZh9 ZaTbQWxQjPVdA== Message-ID: Date: Mon, 29 Jun 2026 19:43:53 +0200 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 2/3] mm: drop pte_clear_not_present_full() To: Andrew Morton Cc: "David S. Miller" , Andreas Larsson , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Jann Horn , Peter Zijlstra , "Oscar Salvador (SUSE)" , sparclinux@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20260629-clear_not_present_full_ptes-v2-0-96089871a1e7@kernel.org> <20260629-clear_not_present_full_ptes-v2-2-96089871a1e7@kernel.org> <20260629102215.09605f0e9ef66c5f58fe0932@linux-foundation.org> 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: <20260629102215.09605f0e9ef66c5f58fe0932@linux-foundation.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit On 6/29/26 19:22, Andrew Morton wrote: > On Mon, 29 Jun 2026 15:49:48 +0200 "David Hildenbrand (Arm)" wrote: > >> In general, there is no good reason to do anything special when clearing >> non-present PTEs. >> >> In theory, HW that does have to invalidate TLBs for non-present PTEs could >> benefit from a "full" parameter, but fortunately >> pte_clear_not_present_full() is not wired up anymore ... and there would >> have to be something very convincing for us to care about that to re-add >> it. >> >> So, let's just use pte_clear() directly now. To avoid the compiler >> complaining on some configs about unused "addr" parameter, silence that >> here. > > Wait, which configs do that? > >> @@ -1022,8 +1007,10 @@ static inline void pte_clear_not_present_full(struct mm_struct *mm, >> static inline void clear_not_present_full_ptes(struct mm_struct *mm, >> unsigned long addr, pte_t *ptep, unsigned int nr, int full) >> { >> + (void)addr; >> + > > We heavily rely on this warning not happening. > > eg, one of thousands: > > static inline bool page_range_contiguous(const struct page *page, > unsigned long nr_pages) > { > return true; > } > > So... what's happening here? "nr_pages" are not modified in the function, so the compile does not complain. See below. A private build bot barked at me after v1 for arm-linux-gnueabi-gcc openrisc-allnoconfig um-allmodconfig For example: https://lore.kernel.org/all/202606121420.Wke8Ipgx-lkp@intel.com/ All errors (new ones prefixed by >>): In file included from include/linux/kasan.h:38, from include/linux/slab.h:264, from lib/test_bitops.c:12: include/linux/pgtable.h: In function 'clear_not_present_full_ptes': >> include/linux/pgtable.h:974:31: error: parameter 'addr' set but not used [-Werror=unused-but-set-parameter=] 974 | unsigned long addr, pte_t *ptep, unsigned int nr, int full) | ~~~~~~~~~~~~~~^~~~ cc1: all warnings being treated as errors The problem is that addr is updated (written) in the function but never read. This becomes visible once pte_clear() is a macro instead of a function. arch/arm/include/asm/pgtable.h:#define pte_clear(mm,addr,ptep) set_pte_ext(ptep, __pte(0), 0) "(void) addr" silences bots. An alternative would be to find all such macros and convert them into (assuming inline function is non-trivial) #define pte_clear(mm,addr,ptep) ((void)addr, set_pte_ext(ptep, __pte(0), 0)) Something I wanted to avoid for this simple patch here that just removes one function indirection. -- Cheers, David