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 334ADC00140 for ; Thu, 18 Aug 2022 20:47:55 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 911988D0003; Thu, 18 Aug 2022 16:47:54 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 8C1618D0002; Thu, 18 Aug 2022 16:47:54 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 78A568D0003; Thu, 18 Aug 2022 16:47:54 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 6A5E18D0002 for ; Thu, 18 Aug 2022 16:47:54 -0400 (EDT) Received: from smtpin21.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 3C59A8236B for ; Thu, 18 Aug 2022 20:47:54 +0000 (UTC) X-FDA: 79813900068.21.1D21A2F Received: from mga12.intel.com (mga12.intel.com [192.55.52.136]) by imf01.hostedemail.com (Postfix) with ESMTP id 1F50943920 for ; Thu, 18 Aug 2022 20:21:38 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1660854100; x=1692390100; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=llLrcHc/wK3CfmeEcVnkYQChSaB5jpfMLinYxM/52ds=; b=JIg+Gjn7RoUFRq3+Zg8stZid2X9nomjusWTKna2gaQUpIyprafhdFEaQ AsXQW4lg7zxIIEW2o/qPYl+ABoXVfBJiLsTZ7mjfs/UorA5a/7VtZf+vs VUPZ4pl1s5/9c+OC5cOKtfxjKdgK2pv1/zDL56if2VV/2a/CwIOptjgDH le0AVrC+t4yYPqir1K/Z628FQIawlS1LWwmEKn1sIXJ1vIZSfDNL/+viK jHex9i0ESqhe4uRAE0YOEYC+wfwFYM3T9srvdV5gU5hsDSQqTsjawHztt lHt2cpjvcna4njj3FORrONuefftNQc6o9vtI5Iw/8xLWstXLWr4+TfVr9 Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10443"; a="272582262" X-IronPort-AV: E=Sophos;i="5.93,247,1654585200"; d="scan'208";a="272582262" Received: from fmsmga006.fm.intel.com ([10.253.24.20]) by fmsmga106.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Aug 2022 09:39:20 -0700 X-IronPort-AV: E=Sophos;i="5.93,247,1654585200"; d="scan'208";a="853473562" Received: from amalikya-mobl.amr.corp.intel.com (HELO [10.212.238.171]) ([10.212.238.171]) by fmsmga006-auth.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 18 Aug 2022 09:39:20 -0700 Message-ID: <8a09b9d5-d5c6-7a1f-1e44-9525b5b18661@intel.com> Date: Thu, 18 Aug 2022 09:39:19 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:91.0) Gecko/20100101 Thunderbird/91.11.0 Subject: Re: [PATCH v3 5/7] mm: Remember young/dirty bit for page migrations Content-Language: en-US To: Nadav Amit , Peter Xu Cc: "Huang, Ying" , Linux MM , LKML , Minchan Kim , David Hildenbrand , Andrew Morton , Hugh Dickins , Vlastimil Babka , Andrea Arcangeli , Andi Kleen , "Kirill A . Shutemov" , Dave Hansen References: <20220809220100.20033-1-peterx@redhat.com> <20220809220100.20033-6-peterx@redhat.com> <87pmh6dwdr.fsf@yhuang6-desk2.ccr.corp.intel.com> <5B21352C-2BE6-4070-BB6B-C1B7A5D4D225@gmail.com> From: Dave Hansen In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1660854100; 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=ZQOSbQfBlKbGH45A5LkVu6J6WXqUA2QfPIm5YpA+XFI=; b=tktSRVsozuLSAvT+6IC9TtwSAmC94WsDSzh/0BnDXNKEbah+LSUa+/q3BkOHFi0dvWmWNP QvJ91q/+1w/S+brv6lWN+sTRO5NEp6Qv5Ng+9xm8nvCYz+FPFH8Zdl2X1Lvd4z8vhyVORI 3fD/xSLqnH1GiA57mTY2Lm6fL0HCMNY= ARC-Authentication-Results: i=1; imf01.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=JIg+Gjn7; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf01.hostedemail.com: domain of dave.hansen@intel.com designates 192.55.52.136 as permitted sender) smtp.mailfrom=dave.hansen@intel.com ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1660854100; a=rsa-sha256; cv=none; b=Re2Xb9/chb8egy/Rihq8Ldk93LWecUOiDBwcsRw7wQYmoSDzJbXcMoJLTjjOXupI2KT9kt p/1p+wUEu8NQX1dS2FVj+YuEVXlwFum4D/yLpP6O1XnEtte9HHpJvgBCtD+2XFIPffYdsO u+W6n1J9zExIy0Lu4k9L6DsqhCb18F4= X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 1F50943920 X-Stat-Signature: ga7b4q8ipm9fumgq35j7n48poi6yoy14 Authentication-Results: imf01.hostedemail.com; dkim=none ("invalid DKIM record") header.d=intel.com header.s=Intel header.b=JIg+Gjn7; dmarc=pass (policy=none) header.from=intel.com; spf=pass (imf01.hostedemail.com: domain of dave.hansen@intel.com designates 192.55.52.136 as permitted sender) smtp.mailfrom=dave.hansen@intel.com X-Rspam-User: X-HE-Tag: 1660854098-870664 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 8/15/22 14:03, Nadav Amit wrote: >> >> At least on x86, the hardware is not supposed to do so. The only case I >> remember (and sometimes misremembers) is with KNL erratum, which perhaps >> needs to be considered: >> >> https://lore.kernel.org/all/20160708001911.9A3FD2B6@viggo.jf.intel.com/ > I keep not remembering this erratum correctly. IIRC, the erratum says that > the access/dirty might be set, but it does not mean that a write is possible > after the PTE is cleared (i.e., the dirty/access might be set on the > non-present PTE, but the access itself would fail). So it is not an issue in > this case - losing A/D would not impact correctness since the access should > fail. > > Dave Hansen hates when I get confused with this one, but I cc him if he > wants to confirm. Right. The issue is strictly with the page walker setting Accessed/Dirty in a racy way. The TLB still has accurate contents at all times.