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=-3.8 required=3.0 tests=BAYES_00, 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 010DAC433E0 for ; Tue, 16 Mar 2021 16:37:06 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 8BB356510C for ; Tue, 16 Mar 2021 16:37:05 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8BB356510C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.intel.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 1FAC96B006E; Tue, 16 Mar 2021 12:37:05 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 1AB376B0070; Tue, 16 Mar 2021 12:37:05 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 0AC306B0071; Tue, 16 Mar 2021 12:37:05 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0243.hostedemail.com [216.40.44.243]) by kanga.kvack.org (Postfix) with ESMTP id E2BAB6B006E for ; Tue, 16 Mar 2021 12:37:04 -0400 (EDT) Received: from smtpin08.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay05.hostedemail.com (Postfix) with ESMTP id A87FF1806310E for ; Tue, 16 Mar 2021 16:37:04 +0000 (UTC) X-FDA: 77926291968.08.B288D33 Received: from mga11.intel.com (mga11.intel.com [192.55.52.93]) by imf11.hostedemail.com (Postfix) with ESMTP id 895B320053EF for ; Tue, 16 Mar 2021 16:36:54 +0000 (UTC) IronPort-SDR: LxeqfO0BV7EmzjfB9HVu9zC9oAlm5onUM+vNGU5qIM7j/W+C+WncWUVSH50up5sAtVDc+BHnSz 0eoKTejQJ8GQ== X-IronPort-AV: E=McAfee;i="6000,8403,9925"; a="185931563" X-IronPort-AV: E=Sophos;i="5.81,254,1610438400"; d="scan'208";a="185931563" Received: from orsmga001.jf.intel.com ([10.7.209.18]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Mar 2021 09:36:50 -0700 IronPort-SDR: 47yQZkdZlJBWElY3HQzRhArOOMFs3mSApsmiAqOZm/AE1AC8FEuG/8QSCxym4aZ9LhICvER6EN oXc+CGXBvj+Q== X-IronPort-AV: E=Sophos;i="5.81,254,1610438400"; d="scan'208";a="449775269" Received: from tassilo.jf.intel.com ([10.54.74.11]) by orsmga001-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 16 Mar 2021 09:36:50 -0700 Date: Tue, 16 Mar 2021 09:36:49 -0700 From: Andi Kleen To: Matthew Wilcox Cc: linux-mm@kvack.org, "Kirill A. Shutemov" , Hugh Dickins Subject: Re: File THP and HWPoison Message-ID: <20210316163649.GR203350@tassilo.jf.intel.com> References: <20210316140947.GA3420@casper.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210316140947.GA3420@casper.infradead.org> X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: 895B320053EF X-Stat-Signature: ry9ha9zenec737eawtggmz8fs8jt4cyj Received-SPF: none (linux.intel.com>: No applicable sender policy available) receiver=imf11; identity=mailfrom; envelope-from=""; helo=mga11.intel.com; client-ip=192.55.52.93 X-HE-DKIM-Result: none/none X-HE-Tag: 1615912614-736665 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: > So we now map the PMD-sized page into userspace, even though it has a > HWPoison in it. Yes that's bad. It might panic the system. > > I think there are two things that we should be doing: > > 1. Attempt to split THPs which are file-backed. That makes most of this > problem disappear because there won't be THPs with HWPoison, mostly. That seems simple and sensible. > 2. When the THP fails to split, use a spare page flag to indicate that > the THP contains a HWPoison bit in one of its subpages. There are a > lot of PF_SECOND flags available for this purpose. Why should it fail? I thought splitting always succeeds. -Andi