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=-10.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,MENTIONS_GIT_HOSTING, NICE_REPLY_A,SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1 autolearn=ham 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 8302DC4743C for ; Wed, 23 Jun 2021 12:33:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 6AD1B6108E for ; Wed, 23 Jun 2021 12:33:06 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230450AbhFWMfW (ORCPT ); Wed, 23 Jun 2021 08:35:22 -0400 Received: from regular1.263xmail.com ([211.150.70.199]:48402 "EHLO regular1.263xmail.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S230402AbhFWMfU (ORCPT ); Wed, 23 Jun 2021 08:35:20 -0400 Received: from localhost (unknown [192.168.167.224]) by regular1.263xmail.com (Postfix) with ESMTP id D2222125B; Wed, 23 Jun 2021 20:32:55 +0800 (CST) X-MAIL-GRAY: 0 X-MAIL-DELIVERY: 1 X-ADDR-CHECKED4: 1 X-SKE-CHECKED: 1 X-ABS-CHECKED: 1 X-ANTISPAM-LEVEL: 2 Received: from [10.4.23.82] (unknown [58.240.82.166]) by smtp.263.net (postfix) whith ESMTP id P4529T140205619136256S1624451574785705_; Wed, 23 Jun 2021 20:32:55 +0800 (CST) X-IP-DOMAINF: 1 X-UNIQUE-TAG: <09e2cf980420933e90fdf735905f1bf3> X-RL-SENDER: wubian@uniontech.com X-SENDER: wubian@uniontech.com X-LOGIN-NAME: wubian@uniontech.com X-FST-TO: will.deacon@arm.com X-RCPT-COUNT: 4 X-SENDER-IP: 58.240.82.166 X-ATTACHMENT-NUM: 0 X-System-Flag: 0 Subject: Re: [PATCH] uio: Fix bus error that access memory mapped by physical To: Greg KH Cc: linux-kernel@vger.kernel.org, catalin.marinas@arm.com, will.deacon@arm.com References: <20210623065214.4525-1-wubian@uniontech.com> <5a2737e1-2a77-98b0-eea7-eae04d7a9fba@uniontech.com> From: wubian Message-ID: Date: Wed, 23 Jun 2021 20:32:55 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.5.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2021/6/23 下午5:25, Greg KH wrote: > A: Because it messes up the order in which people normally read text. > Q: Why is top-posting such a bad thing? > A: Top-posting. > Q: What is the most annoying thing in e-mail? > > A: No. > Q: Should I include quotations after my reply? > > http://daringfireball.net/2007/07/on_top > > On Wed, Jun 23, 2021 at 04:49:16PM +0800, wubian wrote: >> First,thanks for your reply >> >> I haven’t found this problem on the x86 platform. I only found it on arm64. >> I used gdb to track memset and found that the bus error in >> glibc/sysdeps/aarch64/memset.S: dc zva, dst; reference "Architecture >> Reference ManualArmv8, for Armv8-A architecture profile" manual found that >> the dc assembly instruction（performance optimization） is related to the >> operation of the cache, that is to say, there is a bus error in the >> operation of the cache, and then check the "ARM Cortex-A Series Programmer's >> Guide for ARMv8-A " manual, found that the armv8 architecture cache has data >> cache and write buffer, and there are two operation modes write-back and >> write-through, write operations in these two modes, the data flow will pass >> through the write buffer, and pgprot_noncached will prohibit data Cache and >> write buffer, this causes the dc command in memset to fail (bus error), and >> pgprot_writecombine does not prohibit write buffer, so the dc command in >> memset is successfully operated when pgprot_writecombine is used. > > Are you sure this is not just a specific hardware platform issue? Are > you sure this is going to be correct for _ALL_ arm64 systems? > > Perhaps get the arm64 developers to agree with what is happening here as > this is the first time anyone has reported this problem. > > What specific platform are you using that this issue happens on? > > thanks, > > greg k-h > > I apologize for the kernel mail reply format problem, I will pay attention to it in the future. I only found this problem on Huawei Kunpeng 920 cpu at present, and found that some people have raised similar problems on the Internet. link：https://github.com/ikwzm/udmabuf/issues/31 @Catalin Marinas @Will Deacon Has anyone reported a similar problem on the arm64 platform?