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 E83A2C5479D for ; Wed, 11 Jan 2023 23:27:54 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235863AbjAKX1x (ORCPT ); Wed, 11 Jan 2023 18:27:53 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:36360 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235619AbjAKX1x (ORCPT ); Wed, 11 Jan 2023 18:27:53 -0500 Received: from mga17.intel.com (mga17.intel.com [192.55.52.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 466843D5CB; Wed, 11 Jan 2023 15:27:52 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=intel.com; i=@intel.com; q=dns/txt; s=Intel; t=1673479672; x=1705015672; h=message-id:date:mime-version:subject:to:cc:references: from:in-reply-to:content-transfer-encoding; bh=n4DiTA+fkM0MEW9fB8q/JyMf0tXVGfHCcAWyb5AraTs=; b=oBE7/PItJtUPZoqGQiGH1/kxzty7NhqBrDts41Xsdy979LyJlOmYyG4m hq9uLkKUhc9xvLcHg3lE07aetClZR16UftbVnUkbMIzc/7tBm2G/LcQ7c UYi7yCVUmgJ6CH628NQ7u1w7XteJlAJM1dxhZWfQ5NNdk0/Vxy7bECklY skENUXQhtk3H70JOlKMLOkLF7dRBxl+ItmVyNo8AnnewYIqu4OMtSd7q4 BcSJZs9jcUGh/6GgdseFU6iHud6kHBFuK8FngBPUI7v28Uvre6pZqtdVJ k1NRi307RQWy2J7dkVMvdAzvIREIJFz7HO221fCfT2OCEpKGDptmF3XHQ Q==; X-IronPort-AV: E=McAfee;i="6500,9779,10586"; a="303937922" X-IronPort-AV: E=Sophos;i="5.96,318,1665471600"; d="scan'208";a="303937922" Received: from orsmga007.jf.intel.com ([10.7.209.58]) by fmsmga107.fm.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2023 15:27:51 -0800 X-IronPort-AV: E=McAfee;i="6500,9779,10586"; a="650918133" X-IronPort-AV: E=Sophos;i="5.96,318,1665471600"; d="scan'208";a="650918133" Received: from mabir-mobl.amr.corp.intel.com (HELO [10.209.115.16]) ([10.209.115.16]) by orsmga007-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 11 Jan 2023 15:27:51 -0800 Message-ID: <880c4d3c-86d2-082c-bb58-8212adc67ff3@linux.intel.com> Date: Wed, 11 Jan 2023 15:27:51 -0800 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0 Thunderbird/102.4.2 Subject: Re: [PATCH V1] PCI/AER: Configure ECRC only AER is native Content-Language: en-US To: Bjorn Helgaas Cc: Vidya Sagar , bhelgaas@google.com, ruscur@russell.cc, oohall@gmail.com, treding@nvidia.com, jonathanh@nvidia.com, mmaddireddy@nvidia.com, kthota@nvidia.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, vsethi@nvidia.com, linuxppc-dev@lists.ozlabs.org, sagar.tv@gmail.com References: <20230111231033.GA1714672@bhelgaas> From: Sathyanarayanan Kuppuswamy In-Reply-To: <20230111231033.GA1714672@bhelgaas> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org Hi, On 1/11/23 3:10 PM, Bjorn Helgaas wrote: > On Wed, Jan 11, 2023 at 01:42:21PM -0800, Sathyanarayanan Kuppuswamy wrote: >> On 1/11/23 12:31 PM, Vidya Sagar wrote: >>> As the ECRC configuration bits are part of AER registers, configure >>> ECRC only if AER is natively owned by the kernel. >> >> ecrc command line option takes "bios/on/off" as possible options. It >> does not clarify whether "on/off" choices can only be used if AER is >> owned by OS or it can override the ownership of ECRC configuration >> similar to pcie_ports=native option. Maybe that needs to be clarified. > > Good point, what do you think of an update like this: > > diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt > index 6cfa6e3996cf..f7b40a439194 100644 > --- a/Documentation/admin-guide/kernel-parameters.txt > +++ b/Documentation/admin-guide/kernel-parameters.txt > @@ -4296,7 +4296,9 @@ > specified, e.g., 12@pci:8086:9c22:103c:198f > for 4096-byte alignment. > ecrc= Enable/disable PCIe ECRC (transaction layer > - end-to-end CRC checking). > + end-to-end CRC checking). Only effective > + if OS has native AER control (either granted by > + ACPI _OSC or forced via "pcie_ports=native"). > bios: Use BIOS/firmware settings. This is the > the default. > off: Turn ECRC off Looks fine. But do we even need "bios" option? Since it is the default value, I am not sure why we need to list that as an option again. IMO this could be removed. > > I don't know whether the "ecrc=" parameter is really needed. If we > were adding it today, I would ask "why not enable ECRC wherever it is > supported?" If there are devices where it's broken, we could always > add quirks to disable it on a case-by-case basis. Checking the original patch which added it, it looks like the intention is to give option to boost performance over integrity. commit 43c16408842b0eeb367c23a6fa540ce69f99e347 Author: Andrew Patterson Date: Wed Apr 22 16:52:09 2009 -0600 PCI: Add support for turning PCIe ECRC on or off Adds support for PCI Express transaction layer end-to-end CRC checking (ECRC). This patch will enable/disable ECRC checking by setting/clearing the ECRC Check Enable and/or ECRC Generation Enable bits for devices that support ECRC. The ECRC setting is controlled by the "pci=ecrc=" command-line option. If this option is not set or is set to 'bios", the enable and generation bits are left in whatever state that firmware/BIOS set them to. The "off" setting turns them off, and the "on" option turns them on (if the device supports it). Turning ECRC on or off can be a data integrity versus performance tradeoff. In theory, turning it on will catch more data errors, turning it off means possibly better performance since CRC does not need to be calculated by the PCIe hardware and packet sizes are reduced. > > But I think the patch below is the right thing to do for now. Vidya, Agree. > did you trip over an issue because of this, e.g., a conflict between > firmware use of AER and Linux use of it? If so, maybe we could > mention a symptom on the commit log. But my guess is you probably > found this by inspection. > > Bjorn > >>> Signed-off-by: Vidya Sagar >>> --- >>> drivers/pci/pcie/aer.c | 3 +++ >>> 1 file changed, 3 insertions(+) >>> >>> diff --git a/drivers/pci/pcie/aer.c b/drivers/pci/pcie/aer.c >>> index e2d8a74f83c3..730b47bdcdef 100644 >>> --- a/drivers/pci/pcie/aer.c >>> +++ b/drivers/pci/pcie/aer.c >>> @@ -184,6 +184,9 @@ static int disable_ecrc_checking(struct pci_dev *dev) >>> */ >>> void pcie_set_ecrc_checking(struct pci_dev *dev) >>> { >>> + if (!pcie_aer_is_native(dev)) >>> + return; >>> + >>> switch (ecrc_policy) { >>> case ECRC_POLICY_DEFAULT: >>> return; >> >> -- >> Sathyanarayanan Kuppuswamy >> Linux Kernel Developer -- Sathyanarayanan Kuppuswamy Linux Kernel Developer