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 6C093C44508 for ; Tue, 14 Jul 2026 10:54:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4B9A36B0096; Tue, 14 Jul 2026 06:54:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 490936B0098; Tue, 14 Jul 2026 06:54:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 3801F6B0099; Tue, 14 Jul 2026 06:54:48 -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 0863A6B0096 for ; Tue, 14 Jul 2026 06:54:47 -0400 (EDT) Received: from smtpin10.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay10.hostedemail.com (Postfix) with ESMTP id 7EEBBC0315 for ; Tue, 14 Jul 2026 10:54:47 +0000 (UTC) X-FDA: 84987074214.10.1D3134B Received: from sea.source.kernel.org (sea.source.kernel.org [172.234.252.31]) by imf20.hostedemail.com (Postfix) with ESMTP id AD6001C0009 for ; Tue, 14 Jul 2026 10:54:45 +0000 (UTC) Authentication-Results: imf20.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=G62+q4R0; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf20.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1784026485; 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=BE9Tn1RAp+IvoGH4WDLW9L8P6c+reQ5yX7yO2HvT8Kk=; b=O3cmKPrPX91VSGtjEBwHWST4FnenU5avVWrxd+TiZGBZl+5pZDnkjjDIscTuG/7Bj+1FsF 4PbnOPzikoslyzhP4ITf3JwmKY9XnAPQm6KPoViVMcbv/38gcYbHaTjALU/wXaV+umlKJy wJu9VLoC3nGQ5ujDPGH7POXlBGff/Go= ARC-Authentication-Results: i=1; imf20.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20260515 header.b=G62+q4R0; dmarc=pass (policy=quarantine) header.from=kernel.org; spf=pass (imf20.hostedemail.com: domain of david@kernel.org designates 172.234.252.31 as permitted sender) smtp.mailfrom=david@kernel.org ARC-Seal: i=1; a=rsa-sha256; d=hostedemail.com; s=arc-20220608; cv=none; t=1784026485; b=fYzU3Geg+iS4wBkb1c3RRCFtdUYADN07q9QO4ZaaTPIpGjGlslP+d2kc3wJ6waAWkah5Lb B4lGszm4+FjJ8873J5u3QFjyvFbB55K1CShIFm0aOvApoxYWTZM4SUob12SWYbsmPoIaZg NKXW2IQGfOptJ7tjDKPp1ZefkyaDDCY= Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) by sea.source.kernel.org (Postfix) with ESMTP id 741C1419CB; Tue, 14 Jul 2026 10:54:44 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 294991F000E9; Tue, 14 Jul 2026 10:54:29 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1784026484; bh=BE9Tn1RAp+IvoGH4WDLW9L8P6c+reQ5yX7yO2HvT8Kk=; h=Date:Subject:To:Cc:References:From:In-Reply-To; b=G62+q4R01qBeZPrRNev9vE4OIHnXH7tAR6mXURlQFZOUnZg764GFzh5Ws+CzndRp4 6H5eX5vAbkjRrtpWKwbBi9XaZvwVe+KWg4XH1UQdflJKeI5T18qjLvG9xw+YmRCgnz DpRikfkfs/jBBxY/QptbK/URo8iNoyoxP3bKNmBGo2YuJK2Y6G4uoCSNqoC/EnVykR hVtRmY3TGkSaiYI3wuePNIm9SOdqK+DlYhJJU5CDgz6DkBceaTBpNGAuSF/E7EDSVp 0uMrFO+GfdEin9HAT0QicMbToGASgZQCdGjyxVVYSyDCGYH61NzH6E07faEz3sSD4U bZb+fKYzllKhg== Message-ID: Date: Tue, 14 Jul 2026 12:54:28 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH 02/34] ARM: mm: make 2-level pgd_t a scalar To: Pedro Falcato , Yeoreum Yun Cc: linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, loongarch@lists.linux.dev, linux-mips@vger.kernel.org, linux-arch@vger.kernel.org, kvm-riscv@lists.infradead.org, linux-riscv@lists.infradead.org, x86@kernel.org, linux-mm@kvack.org, kasan-dev@googlegroups.com, linux-csky@vger.kernel.org, linux-m68k@lists.linux-m68k.org, linux-openrisc@vger.kernel.org, linux@armlinux.org.uk, akpm@linux-foundation.org, ankur.a.arora@oracle.com, rppt@kernel.org, linmag7@gmail.com, chleroy@kernel.org, klarasmodin@gmail.com, chenhuacai@kernel.org, kernel@xen0n.name, kas@kernel.org, zhangtianyang@loongson.cn, wangyuli@aosc.io, tsbogend@alpha.franken.de, ljs@kernel.org, jgg@ziepe.ca, catalin.marinas@arm.com, will@kernel.org, arnd@arndb.de, ryan.roberts@arm.com, pasha.tatashin@soleen.com, rmclure@linux.ibm.com, baolin.wang@linux.alibaba.com, tj@kernel.org, kevin.brodsky@arm.com, anup@brainfault.org, atish.patra@linux.dev, pjw@kernel.org, palmer@dabbelt.com, aou@eecs.berkeley.edu, alex@ghiti.fr, dave.hansen@linux.intel.com, luto@kernel.org, peterz@infradead.org, tglx@kernel.org, mingo@redhat.com, bp@alien8.de, hpa@zytor.com, hannes@cmpxchg.org, mhocko@kernel.org, qi.zheng@linux.dev, shakeel.butt@linux.dev, kasong@tencent.com, baohua@kernel.org, axelrasmussen@google.com, yuanchu@google.com, weixugc@google.com, ryabinin.a.a@gmail.com, glider@google.com, andreyknvl@gmail.com, dvyukov@google.com, vincenzo.frascino@arm.com, anshuman.khandual@arm.com, yang@os.amperecomputing.com, chaitanyas.prakash@arm.com, ardb@kernel.org, guoren@kernel.org, yang.li85200@gmail.com, viro@zeniv.linux.org.uk, dinguyen@kernel.org, schuster.simon@siemens-energy.com, wangruikang@iscas.ac.cn, junhui.liu@pigmoral.tech, muchun.song@linux.dev, vishal.moola@gmail.com, namcao@linutronix.de, pavel@kernel.org, djbw@kernel.org, yu-cheng.yu@intel.com, baolu.lu@linux.intel.com, Jonathan.Cameron@huawei.com, coxu@redhat.com, andreas@gaisler.com, liam@infradead.org, vbabka@kernel.org, surenb@google.com, mhocko@suse.com, geert@linux-m68k.org, shorne@gmail.com, jonas@southpole.se, stefan.kristiansson@saunalahti.fi References: <20260713135614.1618183-1-yeoreum.yun@arm.com> <20260713135614.1618183-3-yeoreum.yun@arm.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-Server: rspam06 X-Rspamd-Queue-Id: AD6001C0009 X-Stat-Signature: o6bp5n3hcitgo6w5zw9ackgx8ak6u1bf X-Rspam-User: X-HE-Tag: 1784026485-247582 X-HE-Meta: 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 o+foPlEg 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 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On 7/14/26 12:26, Pedro Falcato wrote: > On Mon, Jul 13, 2026 at 02:55:41PM +0100, Yeoreum Yun wrote: >> From: "David Hildenbrand (Arm)" >> >> We don't want pgd_t to be an array, as it prohibits returning it from a >> function, like pgdp_get(). >> >> So let's just use an u64, and extract the right 32bit value in >> pgd_val(). >> >> Leave the STRICT_MM_TYPECHECKS case alone for now. > > I have to ask: is there a good reason for the STRICT_MM_TYPECHECKS ifdef? > > I see the compiler has an awkward time returning a u64 struct (see > https://godbolt.org/z/qejbv6j9a), but if this doesn't work maybe we should > get rid of the STRICT_MM_TYPECHECKS stuff? I seriously doubt anyone is > purposefully toggling it on for testing from time to time. > > If STRICT_MM_TYPEDEFS's worse codegen doesn't matter then maybe we should > permanently toggle it on. >> >> As an alternative, we could use the STRICT_MM_TYPECHECKS approach here >> as well, but using an u64 looks conceptually cleaner, even though >> pgd_val() gets a bit more involved. >> >> Signed-off-by: David Hildenbrand (Arm) >> Signed-off-by: Yeoreum Yun >> --- >> arch/arm/include/asm/pgtable-2level-types.h | 13 ++++++++++--- >> 1 file changed, 10 insertions(+), 3 deletions(-) >> >> diff --git a/arch/arm/include/asm/pgtable-2level-types.h b/arch/arm/include/asm/pgtable-2level-types.h >> index 650e793f41429..02052cef9437a 100644 >> --- a/arch/arm/include/asm/pgtable-2level-types.h >> +++ b/arch/arm/include/asm/pgtable-2level-types.h >> @@ -25,7 +25,7 @@ typedef struct { pteval_t pgprot; } pgprot_t; >> >> #define pte_val(x) ((x).pte) >> #define pmd_val(x) ((x).pmd) >> -#define pgd_val(x) ((x).pgd[0]) >> +#define pgd_val(x) ((x).pgd[0]) >> #define pgprot_val(x) ((x).pgprot) >> >> #define __pte(x) ((pte_t) { (x) } ) >> @@ -36,14 +36,21 @@ typedef struct { pteval_t pgprot; } pgprot_t; >> /* >> * .. while these make it easier on the compiler >> */ >> +typedef u64 pgdval_t; >> + >> typedef pteval_t pte_t; >> typedef pmdval_t pmd_t; >> -typedef pmdval_t pgd_t[2]; >> +typedef pgdval_t pgd_t; >> typedef pteval_t pgprot_t; >> >> #define pte_val(x) (x) >> #define pmd_val(x) (x) >> -#define pgd_val(x) ((x)[0]) >> + >> +static inline pmdval_t pgd_val(pgd_t pgd) >> +{ >> + return (*(pmdval_t (*)[2])&pgd)[0]; > > Ugh. This isn't correct C code. It only works because the kernel passes > -fno-strict-aliasing. So it is correct C code? ;) > I would recommend either forcing a struct here, or > using a u64 with bitmasks/shifts. I had that, but little vs. big endian was annoying. -- Cheers, David