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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 4A4F8C77B6F for ; Thu, 13 Apr 2023 01:50:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229792AbjDMBtk (ORCPT ); Wed, 12 Apr 2023 21:49:40 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44666 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229451AbjDMBtg (ORCPT ); Wed, 12 Apr 2023 21:49:36 -0400 Received: from szxga08-in.huawei.com (szxga08-in.huawei.com [45.249.212.255]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 291785599 for ; Wed, 12 Apr 2023 18:49:34 -0700 (PDT) Received: from dggpemm100009.china.huawei.com (unknown [172.30.72.53]) by szxga08-in.huawei.com (SkyGuard) with ESMTP id 4Pxj8j21Qkz17SGR; Thu, 13 Apr 2023 09:45:57 +0800 (CST) Received: from [10.174.179.24] (10.174.179.24) by dggpemm100009.china.huawei.com (7.185.36.113) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2507.23; Thu, 13 Apr 2023 09:49:31 +0800 Subject: Re: [PATCH -next] mm: hwpoison: support recovery from HugePage copy-on-write faults To: Andrew Morton , Mike Kravetz References: <20230411092741.780679-1-liushixin2@huawei.com> <20230412181350.GA22818@monkey> <20230412145718.0bcb7dd98112a3010711ad0b@linux-foundation.org> CC: Naoya Horiguchi , Tony Luck , Miaohe Lin , Muchun Song , , From: Liu Shixin Message-ID: <28bf1701-d2c6-ee2a-d92d-a603e1a1b3dd@huawei.com> Date: Thu, 13 Apr 2023 09:49:31 +0800 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:45.0) Gecko/20100101 Thunderbird/45.7.1 MIME-Version: 1.0 In-Reply-To: <20230412145718.0bcb7dd98112a3010711ad0b@linux-foundation.org> Content-Type: text/plain; charset="windows-1252" Content-Transfer-Encoding: 7bit X-Originating-IP: [10.174.179.24] X-ClientProxiedBy: dggems706-chm.china.huawei.com (10.3.19.183) To dggpemm100009.china.huawei.com (7.185.36.113) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2023/4/13 5:57, Andrew Morton wrote: > On Wed, 12 Apr 2023 11:13:50 -0700 Mike Kravetz wrote: > >> On 04/11/23 17:27, Liu Shixin wrote: >>> Patch a873dfe1032a ("mm, hwpoison: try to recover from copy-on write faults") >>> introduced a new copy_user_highpage_mc() function, and fix the kernel crash >>> when the kernel is copying a normal page as the result of a copy-on-write >>> fault and runs into an uncorrectable error. But it doesn't work for HugeTLB. >> Andrew asked about user-visible effects. Perhaps, a better way of >> stating this in the commit message might be: >> >> Commit a873dfe1032a ("mm, hwpoison: try to recover from copy-on write >> faults") introduced the routine copy_user_highpage_mc() to gracefully >> handle copying of user pages with uncorrectable errors. Previously, >> such copies would result in a kernel crash. hugetlb has separate code >> paths for copy-on-write and does not benefit from the changes made in >> commit a873dfe1032a. >> >> Modify hugetlb copy-on-write code paths to use copy_mc_user_highpage() >> so that they can also gracefully handle uncorrectable errors in user >> pages. This involves changing the hugetlb specific routine >> ?copy_user_folio()? from type void to int so that it can return an error. >> Modify the hugetlb userfaultfd code in the same way so that it can return >> -EHWPOISON if it encounters an uncorrectable error. > Thanks, but... what are the runtime effects? What does hugetlb > presently do when encountering these uncorrectable error? I have tested the HugeTLB case by using tony's testcase[1](need add a MAP_HUGETLB). Before this patch, the kernel will crash due to the uncorrectable errors. After this patch, if the error occurs in copy-on-write, the process will be killed, if the errors occurs in userfaultfd, it will return -EHWPOISON. Link: https://git.kernel.org/pub/scm/linux/kernel/git/aegl/ras-tools.git [1] > > > . >