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]) by smtp.lore.kernel.org (Postfix) with ESMTP id A3365C3600A for ; Tue, 17 Sep 2024 10:27:56 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 29ABF6B0093; Tue, 17 Sep 2024 06:27:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 24B196B0095; Tue, 17 Sep 2024 06:27:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 139D96B0096; Tue, 17 Sep 2024 06:27:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0014.hostedemail.com [216.40.44.14]) by kanga.kvack.org (Postfix) with ESMTP id E97706B0093 for ; Tue, 17 Sep 2024 06:27:55 -0400 (EDT) Received: from smtpin19.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay03.hostedemail.com (Postfix) with ESMTP id 7A08BA030A for ; 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s=arc-20220608; d=hostedemail.com; t=1726568762; a=rsa-sha256; cv=none; b=FrEU6qe8pebSRDnLzJ1mb5wqWpva0lPlFGFASzM9z4csYaqHUONLTzovt6ecycwI7JBg/s Um1UuiR5YRt8cRU/dOTz2RoKuyWT8E8230NzRCWcFy5efm9REuJw4sfxsSm/prl0Slwo1J C8vQKbjYVNf2qDX/sY9iJGXA3qiDmHc= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=none; spf=pass (imf12.hostedemail.com: domain of ryan.roberts@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=ryan.roberts@arm.com; dmarc=pass (policy=none) header.from=arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 49E8F1007; Tue, 17 Sep 2024 03:28:22 -0700 (PDT) Received: from [10.57.83.157] (unknown [10.57.83.157]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id D1A063F64C; Tue, 17 Sep 2024 03:27:50 -0700 (PDT) Message-ID: Date: Tue, 17 Sep 2024 11:27:49 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH V2 1/7] m68k/mm: Change pmd_val() Content-Language: en-GB To: David Hildenbrand , Anshuman Khandual , linux-mm@kvack.org Cc: Andrew Morton , "Mike Rapoport (IBM)" , Arnd Bergmann , x86@kernel.org, linux-m68k@lists.linux-m68k.org, linux-fsdevel@vger.kernel.org, kasan-dev@googlegroups.com, linux-kernel@vger.kernel.org, linux-perf-users@vger.kernel.org, Geert Uytterhoeven , Guo Ren , Peter Zijlstra References: <20240917073117.1531207-1-anshuman.khandual@arm.com> <20240917073117.1531207-2-anshuman.khandual@arm.com> <4ced9211-2bd7-4257-a9fc-32c775ceffef@redhat.com> From: Ryan Roberts In-Reply-To: <4ced9211-2bd7-4257-a9fc-32c775ceffef@redhat.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Stat-Signature: sea3nbrx7nb4ed3fbrg4zuucdrybamso X-Rspamd-Queue-Id: AAA9940007 X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1726568873-879040 X-HE-Meta: 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 ahrHwBol fFPvzT6ex3Eb7nm6poHSDsWsrPyh5kU5XIcom8OQA0lIt91W0b6dWeTB95/H3/NtwHICE3fVn9mtjKpaBxjzcwYCCwgKxmI3JPf+qX/V8T5Qr8zl05HBp5Gap+fcZYNZHAgdQCSyW7OidqaSGwpI1U1VLi0cPuATmCMIv+pHgdNfWqpeqvC2wpVFDjBZAbrHpTfyTiJtPZFtzfQAZilHJ3rJAj30K30YY8LcXM1WgR1jBs/hewuKZwmMd/wJ9yGfbv6+rgtEO9goJdsBYakHWeHTsJxS8CPls5ZdB9mkz9JamFwQx+T1VZeFCG8hyBNTu1EMcx9pTeUQ4t2x8PxsZRipcgghtu58jPz26GU8uVQqUlgb2Ch6dkwS4ydmcIzjKObuZAj9Xry/yeheKt2UTUXzr7QYICsyVadag79gyLwgMKt4wRmexCFVgVN45Gt/XylRD 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 17/09/2024 11:20, David Hildenbrand wrote: > On 17.09.24 09:31, Anshuman Khandual wrote: >> This changes platform's pmd_val() to access the pmd_t element directly like >> other architectures rather than current pointer address based dereferencing >> that prevents transition into pmdp_get(). >> >> Cc: Geert Uytterhoeven >> Cc: Guo Ren >> Cc: Arnd Bergmann >> Cc: linux-m68k@lists.linux-m68k.org >> Cc: linux-kernel@vger.kernel.org >> Signed-off-by: Anshuman Khandual >> --- >>   arch/m68k/include/asm/page.h | 2 +- >>   1 file changed, 1 insertion(+), 1 deletion(-) >> >> diff --git a/arch/m68k/include/asm/page.h b/arch/m68k/include/asm/page.h >> index 8cfb84b49975..be3f2c2a656c 100644 >> --- a/arch/m68k/include/asm/page.h >> +++ b/arch/m68k/include/asm/page.h >> @@ -19,7 +19,7 @@ >>    */ >>   #if !defined(CONFIG_MMU) || CONFIG_PGTABLE_LEVELS == 3 >>   typedef struct { unsigned long pmd; } pmd_t; >> -#define pmd_val(x)    ((&x)->pmd) >> +#define pmd_val(x)    ((x).pmd) >>   #define __pmd(x)    ((pmd_t) { (x) } ) >>   #endif >>   > > Trying to understand what's happening here, I stumbled over > > commit ef22d8abd876e805b604e8f655127de2beee2869 > Author: Peter Zijlstra > Date:   Fri Jan 31 13:45:36 2020 +0100 > >     m68k: mm: Restructure Motorola MMU page-table layout >         The Motorola 68xxx MMUs, 040 (and later) have a fixed 7,7,{5,6} >     page-table setup, where the last depends on the page-size selected (8k >     vs 4k resp.), and head.S selects 4K pages. For 030 (and earlier) we >     explicitly program 7,7,6 and 4K pages in %tc. >         However, the current code implements this mightily weird. What it does >     is group 16 of those (6 bit) pte tables into one 4k page to not waste >     space. The down-side is that that forces pmd_t to be a 16-tuple >     pointing to consecutive pte tables. >         This breaks the generic code which assumes READ_ONCE(*pmd) will be >     word sized. > > Where we did > >  #if !defined(CONFIG_MMU) || CONFIG_PGTABLE_LEVELS == 3 > -typedef struct { unsigned long pmd[16]; } pmd_t; > -#define pmd_val(x)     ((&x)->pmd[0]) > -#define __pmd(x)       ((pmd_t) { { (x) }, }) > +typedef struct { unsigned long pmd; } pmd_t; > +#define pmd_val(x)     ((&x)->pmd) > +#define __pmd(x)       ((pmd_t) { (x) } ) >  #endif > > So I assume this should be fine I think you're implying that taking the address then using arrow operator was needed when pmd was an array? I don't really understand that if so? Surely: ((x).pmd[0]) would have worked too? I traced back further, and a version of that macro exists with the "address of" and arrow operator since the beginning of (git) time. > > Acked-by: David Hildenbrand >