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=-6.4 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 4C168C48BE5 for ; Mon, 21 Jun 2021 13:01:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 2BFC261156 for ; Mon, 21 Jun 2021 13:01:43 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229876AbhFUND4 (ORCPT ); Mon, 21 Jun 2021 09:03:56 -0400 Received: from mail.kernel.org ([198.145.29.99]:45992 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229640AbhFUNDy (ORCPT ); Mon, 21 Jun 2021 09:03:54 -0400 Received: by mail.kernel.org (Postfix) with ESMTPSA id 8344A600D4; Mon, 21 Jun 2021 13:01:40 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1624280500; bh=W8gtyl5OdibdzPJ1NCZxh+AcF0YQC6Y2zW4xUTjbnVM=; h=Date:From:To:Cc:Subject:In-Reply-To:From; b=rkaSMW08nmJNa2IGQeZFlp3m9VTMGuYz+tJwHa7njfwLre9V+uAbo1asBtfcAdUDO mUnYSg/Zh8ebP4tXcnZ8twrUU33g11JLyU1djKCRkre10DiSRfCtg2QpaUrtmdo7mn MrgHS++4Xod2kAo2vc9OW8QLvpLqu7zmFjDl9nwg1CDQhLQiidtz+FAlK3Q6CMKYGs ACIPGTlGXdQ5PO+Mkzn50OyoCrt0ZiKT0S5w7lAZysJDuyII8gK1HFjpi55AKQ3x9D W9dJj9cnR5ZjBIXJ7Ff3XebP4fJpWvROdygVh2SxXUgp5xbduBoKbn8XziopUuA2eS ERH5If9N7WB4A== Date: Mon, 21 Jun 2021 08:01:35 -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 v7 4/8] PCI/sysfs: Allow userspace to query and set device reset mechanism Message-ID: <20210621130135.GA3288360@bjorn-Precision-5520> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210619135920.h42gp5ie5c2eutfq@archlinux> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Sat, Jun 19, 2021 at 07:29:20PM +0530, Amey Narkhede wrote: > On 21/06/18 03:00PM, Bjorn Helgaas wrote: > > On Tue, Jun 08, 2021 at 11:18:53AM +0530, Amey Narkhede wrote: > > > Add reset_method sysfs attribute to enable user to > > > query and set user preferred device reset methods and > > > their ordering. > > > + if (sysfs_streq(options, "default")) { > > > + for (i = 0; i < PCI_RESET_METHODS_NUM; i++) > > > + reset_methods[i] = reset_methods[i] ? prio-- : 0; > > > + goto set_reset_methods; > > > + } > > > > If you use pci_init_reset_methods() here, you can also get this case > > out of the way early. > > > The problem with alternate encoding is we won't be able to know if > one of the reset methods was disabled previously. For example, > > # cat reset_methods > flr,bus # dev->reset_methods = [3, 5, 0, ...] > # echo bus > reset_methods # dev->reset_methods = [5, 0, 0, ...] > # cat reset_methods > bus > > Now if an user wants to enable flr > > # echo flr > reset_methods # dev->reset_methods = [3, 0, 0, ...] > OR > # echo bus,flr > reset_methods # dev->reset_methods = [5, 3, 0, ...] > > either they need to write "default" first then flr or we will need to > reprobe reset methods each time when user writes to reset_method attribute. Not sure I completely understand the problem here. I think relying on previous state that is invisible to the user is a little problematic because it's hard for the user to predict what will happen. If the user enables a method that was previously "disabled" because the probe failed, won't the reset method itself just fail with -ENOTTY? Is that a problem? > > > + while ((name = strsep(&options, ",")) != NULL) { > > > + if (sysfs_streq(name, "")) > > > + continue; > > > + > > > + name = strim(name); > > > + > > > + for (i = 0; i < PCI_RESET_METHODS_NUM; i++) { > > > + if (reset_methods[i] && > > > + sysfs_streq(name, pci_reset_fn_methods[i].name)) { > > > + reset_methods[i] = prio--; > > > + break; > > > + } > > > + } > > > + > > > + if (i == PCI_RESET_METHODS_NUM) { > > > + kfree(options); > > > + return -EINVAL; > > > + } > > > + } > > > + > > > + if (reset_methods[0] && > > > + reset_methods[0] != PCI_RESET_METHODS_NUM) > > > + pci_warn(pdev, "Device specific reset disabled/de-prioritized by user"); > > > > Is there a specific reason for this warning? Is it just telling the > > user that he might have shot himself in the foot? Not sure that's > > necessary. > > > I think generally presence of device specific reset method means other > methods are potentially broken. Is it okay to skip this? We might want a warning at reset-time if all the methods failed, because that means we may leak state between users. Maybe we also want one here, if *all* reset methods are disabled. I don't really like special treatment of device-specific methods here because it depends on the assumption that "device-specific means all other resets are broken." That's hard to maintain. Bjorn