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 EDC59C32771 for ; Thu, 15 Sep 2022 20:58:44 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 4AF3E6B0071; Thu, 15 Sep 2022 16:58:44 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 45EBE8D0001; Thu, 15 Sep 2022 16:58:44 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 301056B0073; Thu, 15 Sep 2022 16:58:44 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0012.hostedemail.com [216.40.44.12]) by kanga.kvack.org (Postfix) with ESMTP id 1A92E6B0071 for ; Thu, 15 Sep 2022 16:58:44 -0400 (EDT) Received: from smtpin16.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay01.hostedemail.com (Postfix) with ESMTP id D4EC71C725E for ; Thu, 15 Sep 2022 20:58:43 +0000 (UTC) X-FDA: 79915533726.16.41859F0 Received: from ams.source.kernel.org (ams.source.kernel.org [145.40.68.75]) by imf19.hostedemail.com (Postfix) with ESMTP id 484651A008A for ; Thu, 15 Sep 2022 20:58:43 +0000 (UTC) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by ams.source.kernel.org (Postfix) with ESMTPS id 610D7B8225B; Thu, 15 Sep 2022 20:58:41 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 0A6C0C433D7; Thu, 15 Sep 2022 20:58:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1663275520; bh=jc/TYaw+WPP6gHYLDH7WEd6O++ikGzJoRAZP9o8Co78=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=AiKuJ0pUVZax0M8NxOVJiRNYB9QOB0hIswUf9Rx7aEZjIQcqyxU3YQYd1CEiHKqvx CgDQwUOrECpX+88YLy5eMnQpBd1zGGmE/Vy6xJIFuI7knZ+7XtQocgRlD+55dy1HJs wjJ5zRa15PyH0SzLmIgdWUDepJL3U0dk5p2YuWe0= Date: Thu, 15 Sep 2022 13:58:38 -0700 From: Andrew Morton To: Alexander Potapenko Cc: Alexander Viro , Alexei Starovoitov , Andrey Konovalov , Andy Lutomirski , Arnd Bergmann , Borislav Petkov , Christoph Hellwig , Christoph Lameter , David Rientjes , Dmitry Vyukov , Eric Biggers , Eric Dumazet , Greg Kroah-Hartman , Herbert Xu , Ilya Leoshkevich , Ingo Molnar , Jens Axboe , Joonsoo Kim , Kees Cook , Marco Elver , Mark Rutland , Matthew Wilcox , "Michael S. Tsirkin" , Pekka Enberg , Peter Zijlstra , Petr Mladek , Stephen Rothwell , Steven Rostedt , Thomas Gleixner , Vasily Gorbik , Vegard Nossum , Vlastimil Babka , kasan-dev@googlegroups.com, linux-mm@kvack.org, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v7 27/43] kmsan: disable physical page merging in biovec Message-Id: <20220915135838.8ad6df0363ccbd671d9641a1@linux-foundation.org> In-Reply-To: <20220915150417.722975-28-glider@google.com> References: <20220915150417.722975-1-glider@google.com> <20220915150417.722975-28-glider@google.com> X-Mailer: Sylpheed 3.7.0 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1663275523; a=rsa-sha256; cv=none; b=OSwp4uR50fTU9Uxs8N/6CXA28sH2zqHwl+5jkgmzuEdPBIWjdy7oNoWLZA6C0JqOyxaYBs p8LjR4qi3vGSSz4wXwlakyL+7UDOxi8PdnXApWO7pQSJG6OngwV4BFK2d/3SlKiSakn6mn 4JFV2Ya5xFGYMbnNXkaVwj0i64deTuE= ARC-Authentication-Results: i=1; imf19.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=AiKuJ0pU; dmarc=none; spf=pass (imf19.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1663275523; 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=WAzq6T4IcWcpMCLuyAzl7o0sCBrlUXNcyNpqxHsFyQ0=; b=bTLwUTxQbYkT4PqJk2hEp87TDlIka/DRXGtEdjZsHCY4gO/vUsGkTU3Q7vKHHwfBkmt+RQ 9AbX6thYAGNjsH+SGtRJkG2E+0m54ClElgzj8Rc9z1/WzpcEH6wagoGO77uG0aG+zf7GPA Lc8xyJQgAjpag55pIQyecyDAXuIm3WI= X-Stat-Signature: dw1mci4spycxpcuq31drdiuebm4y7xs9 X-Rspamd-Queue-Id: 484651A008A Authentication-Results: imf19.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=AiKuJ0pU; dmarc=none; spf=pass (imf19.hostedemail.com: domain of akpm@linux-foundation.org designates 145.40.68.75 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org X-Rspam-User: X-Rspamd-Server: rspam10 X-HE-Tag: 1663275523-160167 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 Thu, 15 Sep 2022 17:04:01 +0200 Alexander Potapenko wrote: > KMSAN metadata for adjacent physical pages may not be adjacent, > therefore accessing such pages together may lead to metadata > corruption. > We disable merging pages in biovec to prevent such corruptions. > > ... > > --- a/block/blk.h > +++ b/block/blk.h > @@ -88,6 +88,13 @@ static inline bool biovec_phys_mergeable(struct request_queue *q, > phys_addr_t addr1 = page_to_phys(vec1->bv_page) + vec1->bv_offset; > phys_addr_t addr2 = page_to_phys(vec2->bv_page) + vec2->bv_offset; > > + /* > + * Merging adjacent physical pages may not work correctly under KMSAN > + * if their metadata pages aren't adjacent. Just disable merging. > + */ > + if (IS_ENABLED(CONFIG_KMSAN)) > + return false; > + > if (addr1 + vec1->bv_len != addr2) > return false; > if (xen_domain() && !xen_biovec_phys_mergeable(vec1, vec2->bv_page)) What are the runtime effects of this? In other words, how much slowdown is this likely to cause in a reasonable worst-case?