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 45AA3C001DB for ; Sat, 12 Aug 2023 08:26:39 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S235902AbjHLI0e (ORCPT ); Sat, 12 Aug 2023 04:26:34 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:54784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S235175AbjHLI0d (ORCPT ); Sat, 12 Aug 2023 04:26:33 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 9DDD6270E; Sat, 12 Aug 2023 01:26:36 -0700 (PDT) Received: from smtp.kernel.org (relay.kernel.org [52.25.139.140]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits)) (No client certificate requested) by dfw.source.kernel.org (Postfix) with ESMTPS id 293EB602FB; Sat, 12 Aug 2023 08:26:36 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id F3E10C433C7; Sat, 12 Aug 2023 08:26:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1691828795; bh=ZvU+Ji3lEtuChDKihxuZBn05RJ9fLwG7X3gfqnGgG/g=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=MiLzYoIWsPw9lXFle737i8jKOA2d1j8tVQaPJiVoDDrQIKfCgX0Gdm1SMasl//pXa vNl+cpaetVg1KINPFmTvA2AfCAkkpm5OtPiLACyamHfFkDdM6FB+oJkKtPXWtGPVuU 6NsSLQvSsGxNXzoG2omiB/z4yJdq18pUXbiMkjpQ= Date: Sat, 12 Aug 2023 10:26:32 +0200 From: Greg KH To: Lukas Wunner Cc: Alistair Francis , bhelgaas@google.com, linux-pci@vger.kernel.org, Jonathan.Cameron@huawei.com, alex.williamson@redhat.com, christian.koenig@amd.com, kch@nvidia.com, logang@deltatee.com, linux-kernel@vger.kernel.org, Alistair Francis Subject: Re: [PATCH v3] PCI/DOE: Expose the DOE protocols via sysfs Message-ID: <2023081224-famished-devotion-6e0e@gregkh> References: <20230809232851.1004023-1-alistair.francis@wdc.com> <20230810073457.GA26246@wunner.de> <20230812081526.GC9469@wunner.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20230812081526.GC9469@wunner.de> Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Sat, Aug 12, 2023 at 10:15:26AM +0200, Lukas Wunner wrote: > On Thu, Aug 10, 2023 at 11:34:11AM -0400, Alistair Francis wrote: > > On Thu, Aug 10, 2023 at 3:34???AM Lukas Wunner wrote: > > > On Wed, Aug 09, 2023 at 07:28:51PM -0400, Alistair Francis wrote: > > > > --- a/drivers/pci/pci-sysfs.c > > > > +++ b/drivers/pci/pci-sysfs.c > > > > @@ -1226,6 +1227,12 @@ static int pci_create_resource_files(struct pci_dev *pdev) > > > > int i; > > > > int retval; > > > > > > > > +#ifdef CONFIG_PCI_DOE > > > > + retval = doe_sysfs_init(pdev); > > > > + if (retval) > > > > + return retval; > > > > +#endif > > > > + > > > > > > The preferred way to expose PCI sysfs attributes nowadays is to add them > > > to pci_dev_attr_groups[] and use the ->is_visible callback to check > > > whether they're applicable to a particular pci_dev. The alternative > > > via pci_create_resource_files() has race conditions which I think > > > still haven't been fixed. Bjorn recommended the ->is_visible approach > > > in response to the most recent attempt to fix the race: > > > > > > https://lore.kernel.org/linux-pci/20230427161458.GA249886@bhelgaas/ > > > > The is_visible doen't seem to work in this case. > > > > AFAIK is_visible only applies to the attributes under the group. Which > > means that every PCIe device will see a `doe_protos` directory, no > > matter if DOE is supported. > > internal_create_group() in fs/sysfs/group.c does this: > > if (grp->name) { > ... > kn = kernfs_create_dir_ns(kobj->sd, grp->name, ... > > So I'm under the impression that if you set the ->name member of > struct attribute_group, the attributes in that group appear under > a directory of that name. > > In fact, the kernel-doc for struct attribute_group claims as much: > > * struct attribute_group - data structure used to declare an attribute group. > * @name: Optional: Attribute group name > * If specified, the attribute group will be created in > * a new subdirectory with this name. > > So I don't quite understand why you think that "every PCIe device will > see a `doe_protos` directory, no matter if DOE is supported"? > > Am I missing something? I think the issue might be that the directory will be created even if no attributes are present in it due to the is_visable() check not returning any valid files? If so, I had a patch somewhere around here where I was trying to fix that up: https://git.kernel.org/pub/scm/linux/kernel/git/gregkh/driver-core.git/commit/?h=debugfs_cleanup&id=f670945dfbaf353fe068544c31e3fa45575da5b5 but it didn't seem to work properly and kept crashing. I didn't spend much time on looking into it, but if this is an issue, I can work on fixing this properly. thanks, greg k-h