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 X-Spam-Level: X-Spam-Status: No, score=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id D898BC43460 for ; Wed, 14 Apr 2021 21:36:20 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 26D5060FD7 for ; Wed, 14 Apr 2021 21:36:20 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 26D5060FD7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 920886B006C; Wed, 14 Apr 2021 17:36:19 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8D0006B0070; Wed, 14 Apr 2021 17:36:19 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 748C76B0072; Wed, 14 Apr 2021 17:36:19 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0140.hostedemail.com [216.40.44.140]) by kanga.kvack.org (Postfix) with ESMTP id 5B5BA6B006C for ; Wed, 14 Apr 2021 17:36:19 -0400 (EDT) Received: from smtpin14.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id 0AD1382499A8 for ; Wed, 14 Apr 2021 21:36:19 +0000 (UTC) X-FDA: 78032281278.14.DE96A0A Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf30.hostedemail.com (Postfix) with ESMTP id A29ADE000114 for ; Wed, 14 Apr 2021 21:36:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=tiw0DSloQ939N1jQWOHUVqWakm9NGqZcvctG7ish7wk=; b=NsnSuNJytEImhL0Wo1cnKZ+7p9 hHDLgKAJmuc/sHV7PxTbuuD4fJJ/J45u+/OMxBTS22YR7iIa+UYkqxN/gw8DmaU/dhnYxfek0WAl/ EbqdwP8/2gdyPo96cf2wgNpsRvCy2X2e0tY8tuXdetX5UUk2RVgLrDNfo1FCPU5d0nU+b2vDEXV+F R5rW9JgGm8/SUwNGZuq+2tWKp47J0pTlUAu56KYCGGg4qlZ9MsL9iwJxxGMhITMU3iNjoYQVhtdH1 huQUgK3Omj03NxN1K8suu9wQDUZb56zB4+gYivQGVkqHlCi/oYqL/F+XGVdyzo4j22SCP0GWB3riv tV58OZWw==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lWnAy-007fMW-F1; Wed, 14 Apr 2021 21:36:00 +0000 Date: Wed, 14 Apr 2021 22:35:56 +0100 From: Matthew Wilcox To: Jesper Dangaard Brouer Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org, netdev@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-arm-kernel@lists.infradead.org, linux-mips@vger.kernel.org, Ilias Apalodimas , Matteo Croce , Grygorii Strashko , Arnd Bergmann , Christoph Hellwig Subject: Re: [PATCH 1/1] mm: Fix struct page layout on 32-bit systems Message-ID: <20210414213556.GY2531743@casper.infradead.org> References: <20210410205246.507048-1-willy@infradead.org> <20210410205246.507048-2-willy@infradead.org> <20210411114307.5087f958@carbon> <20210411103318.GC2531743@casper.infradead.org> <20210412011532.GG2531743@casper.infradead.org> <20210414101044.19da09df@carbon> <20210414115052.GS2531743@casper.infradead.org> <20210414211322.3799afd4@carbon> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210414211322.3799afd4@carbon> X-Rspamd-Server: rspam01 X-Rspamd-Queue-Id: A29ADE000114 X-Stat-Signature: kxxnoz88bkhuuc18uuqyjwfb8utco343 Received-SPF: none (infradead.org>: No applicable sender policy available) receiver=imf30; identity=mailfrom; envelope-from=""; helo=casper.infradead.org; client-ip=90.155.50.34 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1618436167-454281 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: On Wed, Apr 14, 2021 at 09:13:22PM +0200, Jesper Dangaard Brouer wrote: > (If others want to reproduce). First I could not reproduce on ARM32. > Then I found out that enabling CONFIG_XEN on ARCH=arm was needed to > cause the issue by enabling CONFIG_ARCH_DMA_ADDR_T_64BIT. hmmm ... you should be able to provoke it by enabling ARM_LPAE, which selects PHYS_ADDR_T_64BIT, and config ARCH_DMA_ADDR_T_64BIT def_bool 64BIT || PHYS_ADDR_T_64BIT > struct page { > long unsigned int flags; /* 0 4 */ > > /* XXX 4 bytes hole, try to pack */ > > union { > struct { > struct list_head lru; /* 8 8 */ > struct address_space * mapping; /* 16 4 */ > long unsigned int index; /* 20 4 */ > long unsigned int private; /* 24 4 */ > }; /* 8 20 */ > struct { > dma_addr_t dma_addr; /* 8 8 */ > }; /* 8 8 */ [...] > } __attribute__((__aligned__(8))); /* 8 24 */ > union { > atomic_t _mapcount; /* 32 4 */ > unsigned int page_type; /* 32 4 */ > unsigned int active; /* 32 4 */ > int units; /* 32 4 */ > }; /* 32 4 */ > atomic_t _refcount; /* 36 4 */ > > /* size: 40, cachelines: 1, members: 4 */ > /* sum members: 36, holes: 1, sum holes: 4 */ > /* forced alignments: 1, forced holes: 1, sum forced holes: 4 */ > /* last cacheline: 40 bytes */ > } __attribute__((__aligned__(8))); If you also enable CONFIG_MEMCG or enough options to make LAST_CPUPID_NOT_IN_PAGE_FLAGS true, you'll end up with another 4-byte hole at the end.