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 17DD9C11F68 for ; Fri, 2 Jul 2021 14:49:05 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id EE2BC6140C for ; Fri, 2 Jul 2021 14:49:04 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233044AbhGBOvg (ORCPT ); Fri, 2 Jul 2021 10:51:36 -0400 Received: from mga11.intel.com ([192.55.52.93]:16479 "EHLO mga11.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232381AbhGBOvf (ORCPT ); Fri, 2 Jul 2021 10:51:35 -0400 X-IronPort-AV: E=McAfee;i="6200,9189,10033"; a="205734472" X-IronPort-AV: E=Sophos;i="5.83,317,1616482800"; d="scan'208";a="205734472" Received: from orsmga003.jf.intel.com ([10.7.209.27]) by fmsmga102.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Jul 2021 07:49:02 -0700 X-IronPort-AV: E=Sophos;i="5.83,317,1616482800"; d="scan'208";a="409527191" Received: from tkhalx-mobl.amr.corp.intel.com (HELO [10.252.132.13]) ([10.252.132.13]) by orsmga003-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 02 Jul 2021 07:49:02 -0700 Subject: Re: [PATCH v3 1/2] x86/ioremap: fix the pfn calculation mistake in __ioremap_check_ram() To: Yaohui Wang , tglx@linutronix.de Cc: luto@kernel.org, peterz@infradead.org, mingo@redhat.com, bp@alien8.de, x86@kernel.org, linux-kernel@vger.kernel.org, luoben@linux.alibaba.com, Tom Lendacky , Brijesh Singh References: <20210621123419.2976-1-yaohuiwang@linux.alibaba.com> <20210621123419.2976-2-yaohuiwang@linux.alibaba.com> <94a38542-b639-37e4-1b53-29b59c5ea655@intel.com> <34bae667-180f-ce97-ee55-12e13ff28ca0@linux.alibaba.com> From: Dave Hansen Autocrypt: addr=dave.hansen@intel.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.10.0 MIME-Version: 1.0 In-Reply-To: <34bae667-180f-ce97-ee55-12e13ff28ca0@linux.alibaba.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 7/2/21 3:05 AM, Yaohui Wang wrote: > On 2021/7/1 22:41, Dave Hansen wrote: >> Was this issue found by inspection, or is it causing an actual problem >> in practice? > > This issus truly caused terrible perforamnce downgrade in the practice. > When developing an out of tree module in our testing environment, > invoking ioremap() on normal RAM causes apparent CLI lag. The Unixbench > score also decreases a lot (5x slowdown in the worst case). > > Debugging such performance issue is extremely difficult, especially when > the code of the faulty module itself is already very complex. I tested > the system in many aspects before finally located this problem. Do you know why this check: > if ((res->flags & IORESOURCE_SYSTEM_RAM) != IORESOURCE_SYSTEM_RAM) > return false; did not catch your out-of-tree driver's errant ioremap()?