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=-16.7 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_CR_TRAILER,INCLUDES_PATCH, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=unavailable 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 CAB15C432BE for ; Wed, 28 Jul 2021 18:13:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id AF84F603E9 for ; Wed, 28 Jul 2021 18:13:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230309AbhG1SNi (ORCPT ); Wed, 28 Jul 2021 14:13:38 -0400 Received: from mail.kernel.org ([198.145.29.99]:49798 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229556AbhG1SNh (ORCPT ); Wed, 28 Jul 2021 14:13:37 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 9F2CB603E9; Wed, 28 Jul 2021 18:13:34 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1627496014; bh=P9TGmCBS0wuxkvlhnvMb3ep94V2sHg4ndhlIOEsYpvI=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=FyqBaEFQkl0CmWU9XMmwfG9QcL2snj6dpKkBW788okugWB16M/Iy3s5g8W22DNVK2 bEYTtKN43/nd7HJ5SASDNM1RKZwrNNR3acZK8qpcH7ZQFKj40YvS9WI/+C/B8ek8US yIm5Tu4smegsNQXXpUMowpwvkzcLaSFTpYv03R+wep5w9kkktKgNUnfc5BbfGdwALK IBABu339u0p8C5BpYoMmTF8vIzg8yjce+NeDVES7O+INP6UrKHRJzwOgw29gsJMqgM 5C5xSDtAqej2p7FGgNkXaXUsMCAeDCSYnhFWoIlsE4Y2emZgM013s91YYIGdtFlfG2 jG81tTfVd5VtQ== Date: Wed, 28 Jul 2021 13:13:33 -0500 From: Bjorn Helgaas To: Amey Narkhede Cc: alex.williamson@redhat.com, Raphael Norwitz , linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, kw@linux.com, Shanker Donthineni , Sinan Kaya , Len Brown , "Rafael J . Wysocki" Subject: Re: [PATCH v10 4/8] PCI/sysfs: Allow userspace to query and set device reset mechanism Message-ID: <20210728181333.GA836307@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210728175950.q75qcrfas5mcjych@archlinux> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Jul 28, 2021 at 11:29:50PM +0530, Amey Narkhede wrote: > On 21/07/27 06:28PM, Bjorn Helgaas wrote: > > On Fri, Jul 09, 2021 at 06:08:09PM +0530, Amey Narkhede wrote: > > > Add reset_method sysfs attribute to enable user to query and set user > > > preferred device reset methods and their ordering. > > > > > > Co-developed-by: Alex Williamson > > > Signed-off-by: Alex Williamson > > > Signed-off-by: Amey Narkhede > > > --- > > > Documentation/ABI/testing/sysfs-bus-pci | 19 +++++ > > > drivers/pci/pci-sysfs.c | 103 ++++++++++++++++++++++++ > > > 2 files changed, 122 insertions(+) > > > > > > diff --git a/Documentation/ABI/testing/sysfs-bus-pci b/Documentation/ABI/testing/sysfs-bus-pci > > > index ef00fada2..43f4e33c7 100644 > > > --- a/Documentation/ABI/testing/sysfs-bus-pci > > > +++ b/Documentation/ABI/testing/sysfs-bus-pci > > > @@ -121,6 +121,25 @@ Description: > > > child buses, and re-discover devices removed earlier > > > from this part of the device tree. > > > > > > +What: /sys/bus/pci/devices/.../reset_method > > > +Date: March 2021 > > > +Contact: Amey Narkhede > > > +Description: > > > + Some devices allow an individual function to be reset > > > + without affecting other functions in the same slot. > > > + > > > + For devices that have this support, a file named > > > + reset_method will be present in sysfs. Initially reading > > > + this file will give names of the device supported reset > > > + methods and their ordering. After write, this file will > > > + give names and ordering of currently enabled reset methods. > > > + Writing the name or comma separated list of names of any of > > > + the device supported reset methods to this file will set > > > + the reset methods and their ordering to be used when > > > + resetting the device. Writing empty string to this file > > > + will disable ability to reset the device and writing > > > + "default" will return to the original value. > > > + > > > What: /sys/bus/pci/devices/.../reset > > > Date: July 2009 > > > Contact: Michael S. Tsirkin > > > [...] > > > > + int i; > > > + > > > + if (sysfs_streq(name, "")) > > > + continue; > > > + > > > + name = strim(name); > > > + > > > + for (i = 1; i < PCI_NUM_RESET_METHODS; i++) { > > > + if (sysfs_streq(name, pci_reset_fn_methods[i].name) && > > > + !pci_reset_fn_methods[i].reset_fn(pdev, 1)) { > > > + reset_methods[n++] = i; > > > > Can we build this directly in pdev->reset_methods[] so we don't need > > the memcpy() below? > > > This is to avoid writing partial values directly to dev->reset_methods. > So for example if user writes flr,unsupported_value then > dev->reset_methods should not be modified even though flr is valid reset > method in this example to avoid partial writes. Either operation(in this > case writing supported reset methods to reset_method attr) succeeds > completely or it fails othewise. I guess the question is, if somebody writes flr junk bus and we set the supported methods to "flr bus", is that OK? It seems OK to me; obviously we have to protect ourselves from attack, but over-zealous checking can make things unnecessarily complicated.