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 68D86C0015E for ; Tue, 15 Aug 2023 20:11:05 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S240126AbjHOUKc (ORCPT ); Tue, 15 Aug 2023 16:10:32 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:48928 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S240173AbjHOUKO (ORCPT ); Tue, 15 Aug 2023 16:10:14 -0400 Received: from dfw.source.kernel.org (dfw.source.kernel.org [IPv6:2604:1380:4641:c500::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 334A01BE2; Tue, 15 Aug 2023 13:10:13 -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 B53B665D4A; Tue, 15 Aug 2023 20:10:12 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id BEB47C433C8; Tue, 15 Aug 2023 20:10:11 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1692130212; bh=49CtHvFLjsWdVP/KunpxEt8LNawrL89+unX3+egWjbM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=SVCSHdehYMNtSTV1erQHKXY4UotrI6NWoQqT0HHfEJmYaZRZN92QgUwIJ3xYfODoj piYUzW7kePpvMdmoPuRndNpJ76NlR8sFUtQ6/K+IfPXbDRct9+O9myWLqIiBVaV2Z9 saj1XhW480uTqT7FWgHOynpnh6MOv/A441SvTBcg= Date: Tue, 15 Aug 2023 22:10:09 +0200 From: Greg KH To: Alistair Francis Cc: Lukas Wunner , 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: <2023081538-grab-alongside-ce24@gregkh> References: <20230809232851.1004023-1-alistair.francis@wdc.com> <20230810073457.GA26246@wunner.de> <20230812081526.GC9469@wunner.de> <2023081224-famished-devotion-6e0e@gregkh> <2023081543-clarify-deniable-8de8@gregkh> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org On Tue, Aug 15, 2023 at 03:50:31PM -0400, Alistair Francis wrote: > On Tue, Aug 15, 2023 at 11:11 AM Greg KH wrote: > > > > On Tue, Aug 15, 2023 at 09:44:32AM -0400, Alistair Francis wrote: > > > On Sat, Aug 12, 2023 at 4:26 AM Greg KH wrote: > > > > > > > > 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? > > > > > > Yes, that's what I'm seeing. I see the directory for all PCIe devices > > > > > > This is a WIP that I had: > > > https://github.com/alistair23/linux/commit/61925cd174c31386eaa7e51e3a1be606b38f847c > > > > > > > > > > > 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. > > > > > > That patch sounds like it would fix the issue of empty directories > > > that I'm seeing. Do you mind fixing it up properly? > > > > I am currently unable to do so due to travel and stuff for a few weeks, > > sorry. Feel free to take it and fix the boot crash that is seen with it > > and make it part of your patch series if you can't wait that long. > > No worries. > > It's much harder than I first thought though. There are currently lots > of users who expect the group to remain even if empty, as they > dynamically add/merge properties later. Which is what we end up doing > for DOE as well > > I'll keep looking into this and see if I can figure something out. Yeah, now that I think about it, that's where stuff fell apart for me as well. We should be able to create the group and then only create the file when they are added/merged, so I bet I missed a codepath somewhere. > Would an .attr_is_visible() function pointer for struct > attribute_group something that the kernel would accept? Worst case, yes, that would be acceptable. But try to see where I messed up on the original patch, it should be able to be done automatically somehow... thanks, greg k-h