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=-7.5 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,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 1D360C433E0 for ; Fri, 29 Jan 2021 18:39:42 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id B5ACD64E09 for ; Fri, 29 Jan 2021 18:39:41 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232418AbhA2Sjl (ORCPT ); Fri, 29 Jan 2021 13:39:41 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:24996 "EHLO us-smtp-delivery-124.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S232501AbhA2Sjk (ORCPT ); Fri, 29 Jan 2021 13:39:40 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1611945493; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=o6RgsnGWqDbRx7FOfKlaMYyztEsq7mThGPYbon8eyBE=; b=eDGCAAQqRWVUA4eNbmoz7Qdx3LEYYkKekBsqjL3ommzPR0qFSMTshzAi/+VYQbZKz1iSTC 1VZE2fXmOASrXWAy4n8VfXKFagbcs/o7uImimBlswA25Wse/eoF+bVLHBK16+e//JCXZG8 TW2NrjilfU4wppKoCtvUD/tVF4/KDeo= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-373-FnU8NuaCP02giqCI5tvXtQ-1; Fri, 29 Jan 2021 13:38:09 -0500 X-MC-Unique: FnU8NuaCP02giqCI5tvXtQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 9FC3581CBF3; Fri, 29 Jan 2021 18:38:07 +0000 (UTC) Received: from prarit.bos.redhat.com (prarit-guest.7a2m.lab.eng.bos.redhat.com [10.16.222.26]) by smtp.corp.redhat.com (Postfix) with ESMTP id 93A875D984; Fri, 29 Jan 2021 18:38:05 +0000 (UTC) Subject: Re: [PATCH] pci-driver: Add driver load messages To: Bjorn Helgaas Cc: Leon Romanovsky , bhelgaas@google.com, corbet@lwn.net, linux-doc@vger.kernel.org, linux-pci@vger.kernel.org, mstowe@redhat.com References: <20210126151259.GA2886142@bjorn-Precision-5520> From: Prarit Bhargava Message-ID: Date: Fri, 29 Jan 2021 13:38:03 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 MIME-Version: 1.0 In-Reply-To: <20210126151259.GA2886142@bjorn-Precision-5520> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On 1/26/21 10:12 AM, Bjorn Helgaas wrote: > Hi Prarit, > > On Tue, Jan 26, 2021 at 09:05:23AM -0500, Prarit Bhargava wrote: >> On 1/26/21 8:53 AM, Leon Romanovsky wrote: >>> On Tue, Jan 26, 2021 at 08:42:12AM -0500, Prarit Bhargava wrote: >>>> On 1/26/21 8:14 AM, Leon Romanovsky wrote: >>>>> On Tue, Jan 26, 2021 at 07:54:46AM -0500, Prarit Bhargava wrote: >>>>>> Leon Romanovsky wrote: >>>>>>> On Mon, Jan 25, 2021 at 02:41:38PM -0500, Prarit Bhargava wrote: >>>>>>>> There are two situations where driver load messages are helpful. >>>>>>>> >>>>>>>> 1) Some drivers silently load on devices and debugging driver or system >>>>>>>> failures in these cases is difficult. While some drivers (networking >>>>>>>> for example) may not completely initialize when the PCI driver probe() function >>>>>>>> has returned, it is still useful to have some idea of driver completion. >>>>>>> >>>>>>> Sorry, probably it is me, but I don't understand this use case. >>>>>>> Are you adding global to whole kernel command line boot argument to debug >>>>>>> what and when? >>>>>>> >>>>>>> During boot: >>>>>>> If device success, you will see it in /sys/bus/pci/[drivers|devices]/*. >>>>>>> If device fails, you should get an error from that device (fix the >>>>>>> device to return an error), or something immediately won't work and >>>>>>> you won't see it in sysfs. >>>>>> >>>>>> What if there is a panic during boot? There's no way to get to sysfs. >>>>>> That's the case where this is helpful. >>>>> >>>>> How? If you have kernel panic, it means you have much more worse problem >>>>> than not-supported device. If kernel panic was caused by the driver, you >>>>> will see call trace related to it. If kernel panic was caused by >>>>> something else, supported/not supported won't help here. >>>> >>>> I still have no idea *WHICH* device it was that the panic occurred on. >>> >>> The kernel panic is printed from the driver. There is one driver loaded >>> for all same PCI devices which are probed without relation to their >>> number.> >>> If you have host with ten same cards, you will see one driver and this >>> is where the problem and not in supported/not-supported device. >> >> That's true, but you can also have different cards loading the same driver. >> See, for example, any PCI_IDs list in a driver. >> >> For example, >> >> 10:00.0 RAID bus controller: Broadcom / LSI MegaRAID SAS-3 3008 [Fury] (rev 02) >> 20:00.0 RAID bus controller: Broadcom / LSI MegaRAID SAS-3 3108 [Invader] (rev 02) >> >> Both load the megaraid driver and have different profiles within the >> driver. I have no idea which one actually panicked until removing >> one card. >> >> It's MUCH worse when debugging new hardware and getting a panic >> from, for example, the uncore code which binds to a PCI mapped >> device. One device might work and the next one doesn't. And then >> you can multiply that by seeing *many* panics at once and trying to >> determine if the problem was on one specific socket, die, or core. > > Would a dev_panic() interface that identified the device and driver > help with this? It would but, > > For driver_load_messages, it doesn't seem necessarily PCI-specific. > If we want a message like that, maybe it could be in > driver_probe_device() or similar? There are already a few pr_debug() > calls in that path. There are some enabled by initcall_debug that > include the return value from the probe; would those be close to what > you're looking for? I think this drivers/base/dd.c:727 might suffice. Let me try some tests with that and get back to you. Thanks for the pointers, P. > > Bjorn >