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=-5.3 required=3.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,NICE_REPLY_A,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 85A7AC43619 for ; Mon, 15 Mar 2021 09:46:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 5DDA264EAE for ; Mon, 15 Mar 2021 09:46:02 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229840AbhCOJpi (ORCPT ); Mon, 15 Mar 2021 05:45:38 -0400 Received: from frasgout.his.huawei.com ([185.176.79.56]:2693 "EHLO frasgout.his.huawei.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229673AbhCOJpP (ORCPT ); Mon, 15 Mar 2021 05:45:15 -0400 Received: from fraeml706-chm.china.huawei.com (unknown [172.18.147.207]) by frasgout.his.huawei.com (SkyGuard) with ESMTP id 4DzWXN3sNhz680KG; Mon, 15 Mar 2021 17:36:52 +0800 (CST) Received: from lhreml724-chm.china.huawei.com (10.201.108.75) by fraeml706-chm.china.huawei.com (10.206.15.55) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_CBC_SHA256_P256) id 15.1.2106.2; Mon, 15 Mar 2021 10:45:10 +0100 Received: from [10.210.166.140] (10.210.166.140) by lhreml724-chm.china.huawei.com (10.201.108.75) with Microsoft SMTP Server (version=TLS1_2, cipher=TLS_ECDHE_RSA_WITH_AES_128_GCM_SHA256) id 15.1.2106.2; Mon, 15 Mar 2021 09:45:09 +0000 Subject: Re: arm64 syzbot instances To: Arnd Bergmann , Dmitry Vyukov CC: Mark Rutland , Marc Zyngier , "Will Deacon" , Ard Biesheuvel , Linux ARM , syzkaller , LKML , "Peter Maydell" , =?UTF-8?Q?Alex_Benn=c3=a9e?= References: From: John Garry Message-ID: <48347b4d-9194-16f2-95a0-c3eb55ca9a80@huawei.com> Date: Mon, 15 Mar 2021 09:43:02 +0000 User-Agent: Mozilla/5.0 (Windows NT 10.0; WOW64; rv:68.0) Gecko/20100101 Thunderbird/68.1.2 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset="utf-8"; format=flowed Content-Language: en-US Content-Transfer-Encoding: 7bit X-Originating-IP: [10.210.166.140] X-ClientProxiedBy: lhreml718-chm.china.huawei.com (10.201.108.69) To lhreml724-chm.china.huawei.com (10.201.108.75) X-CFilter-Loop: Reflected Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 12/03/2021 10:52, Arnd Bergmann wrote: > On Fri, Mar 12, 2021 at 11:38 AM Dmitry Vyukov wrote: >> On Fri, Mar 12, 2021 at 11:11 AM Arnd Bergmann wrote: >> >> It does not happen too often on syzbot so far, so let's try to do the >> right thing first. >> I've filed: https://bugs.launchpad.net/qemu/+bug/1918917 >> with a link to this thread. To be fair, I don't fully understand what >> I am talking about, I hope I proxied your description properly. > > Thanks, looks good. I provided a little more detail in a comment there. > > Arnd > . > From looking at the bug report, my impression is that this is a qemu issue, as the logical IO space is mapped to the PCI host bridge IO space, and qemu does not handle accesses to that CPU addressable region at all. As Arnd said. However, we really should not be accessing logical IO ports 0 or 0x2f8 at all via ttyS3 if not enumerated from PCI device at that logical IO port. That is what I think anyway, as who knows what device - if any - really exists at that location. That is why I had this patch to just stop accesses to legacy IO port regions on arm64: https://lore.kernel.org/lkml/1610729929-188490-2-git-send-email-john.garry@huawei.com/ Thanks, John