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 15C61C433EF for ; Thu, 5 May 2022 06:39:57 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S244942AbiEEGnd (ORCPT ); Thu, 5 May 2022 02:43:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53224 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233799AbiEEGn2 (ORCPT ); Thu, 5 May 2022 02:43:28 -0400 Received: from szxga03-in.huawei.com (szxga03-in.huawei.com [45.249.212.189]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7B00633A0C for ; Wed, 4 May 2022 23:39:48 -0700 (PDT) Received: from kwepemi500023.china.huawei.com (unknown [172.30.72.55]) by szxga03-in.huawei.com (SkyGuard) with ESMTP id 4Kv3pc69TXzDqKY; Thu, 5 May 2022 14:35:04 +0800 (CST) Received: from kwepemm600017.china.huawei.com (7.193.23.234) by kwepemi500023.china.huawei.com (7.221.188.76) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 5 May 2022 14:39:45 +0800 Received: from [10.174.179.234] (10.174.179.234) by kwepemm600017.china.huawei.com (7.193.23.234) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2375.24; Thu, 5 May 2022 14:39:44 +0800 Message-ID: <7da54d72-e5fa-41b5-67ea-a0b084e4c94a@huawei.com> Date: Thu, 5 May 2022 14:39:43 +0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:91.0) Gecko/20100101 Thunderbird/91.8.0 Subject: Re: [PATCH -next v4 4/7] arm64: add copy_{to, from}_user to machine check safe To: Catalin Marinas CC: Mark Rutland , James Morse , Andrew Morton , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Robin Murphy , Dave Hansen , Will Deacon , Alexander Viro , Michael Ellerman , "Benjamin Herrenschmidt" , Paul Mackerras , , "H . Peter Anvin" , , , , , Kefeng Wang , Xie XiuQi , Guohanjun References: <20220420030418.3189040-1-tongtiangen@huawei.com> <20220420030418.3189040-5-tongtiangen@huawei.com> From: Tong Tiangen In-Reply-To: Content-Type: text/plain; charset="UTF-8"; format=flowed Content-Transfer-Encoding: 8bit X-Originating-IP: [10.174.179.234] X-ClientProxiedBy: dggems704-chm.china.huawei.com (10.3.19.181) To kwepemm600017.china.huawei.com (7.193.23.234) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 在 2022/5/4 18:26, Catalin Marinas 写道: > On Wed, Apr 20, 2022 at 03:04:15AM +0000, Tong Tiangen wrote: >> Add copy_{to, from}_user() to machine check safe. >> >> If copy fail due to hardware memory error, only the relevant processes are >> affected, so killing the user process and isolate the user page with >> hardware memory errors is a more reasonable choice than kernel panic. > > Just to make sure I understand - we can only recover if the fault is in > a user page. That is, for a copy_from_user(), we can only handle the > faults in the source address, not the destination. At the beginning, I also thought we can only recover if the fault is in a user page. After discussion with a Mark[1], I think no matter user page or kernel page, as long as it is triggered by the user process, only related processes will be affected. According to this understanding, it seems that all uaccess can be recovered. [1]https://patchwork.kernel.org/project/linux-arm-kernel/patch/20220406091311.3354723-6-tongtiangen@huawei.com/ Thanks, Tong. > >> diff --git a/arch/arm64/lib/copy_from_user.S b/arch/arm64/lib/copy_from_user.S >> index 34e317907524..480cc5ac0a8d 100644 >> --- a/arch/arm64/lib/copy_from_user.S >> +++ b/arch/arm64/lib/copy_from_user.S >> @@ -25,7 +25,7 @@ >> .endm >> >> .macro strb1 reg, ptr, val >> - strb \reg, [\ptr], \val >> + USER_MC(9998f, strb \reg, [\ptr], \val) >> .endm > > So if I got the above correctly, why do we need an exception table entry > for the store to the kernel address? >