Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754508AbdDLPXU (ORCPT ); Wed, 12 Apr 2017 11:23:20 -0400 Received: from mail.kernel.org ([198.145.29.136]:45538 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752862AbdDLPXS (ORCPT ); Wed, 12 Apr 2017 11:23:18 -0400 Date: Wed, 12 Apr 2017 10:22:16 -0500 From: Bjorn Helgaas To: Bodong Wang Cc: bhelgaas@google.com, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, saeedm@mellanox.com, Eli Cohen Subject: Re: [v2] PCI: Add an option to control probing of VFs before enabling SR-IOV Message-ID: <20170412152216.GA25197@bhelgaas-glaptop.roam.corp.google.com> References: <1490198038-20465-1-git-send-email-bodong@mellanox.com> <20170411211211.GB14778@bhelgaas-glaptop.roam.corp.google.com> <2e39e1b6-0205-2780-0223-3552d2c871a3@mellanox.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <2e39e1b6-0205-2780-0223-3552d2c871a3@mellanox.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2283 Lines: 56 On Wed, Apr 12, 2017 at 09:37:22AM -0500, Bodong Wang wrote: > On 4/11/2017 4:12 PM, Bjorn Helgaas wrote: > >Hi Bodong, > > > >On Wed, Mar 22, 2017 at 05:53:58PM +0200, bodong@mellanox.com wrote: > >>From: Bodong Wang > >> > >>Sometimes it is not desirable to probe the virtual functions after > >>SRIOV is enabled. This can save host side resource usage by VF > >>instances which would be eventually probed to VMs. > >> > >>Add a new PCI sysfs interface "sriov_probe_vfs" to control that > >>from the PF, all current callers still retain the same functionality. > >>To modify it, echo 0/n/N (disable probe) or 1/y/Y (enable probe) to > >> > >>/sys/bus/pci/devices//sriov_probe_vfs > >Is this basically the same functionality as /sys/bus/pci/drivers_autoprobe, > >but limited to a specific PF? I.e., could we accomplish the same thing > >with the following? > > > > # echo 0 > /sys/bus/pci/devices/DDDD:BB:dd.f/sriov_numvfs > > # echo 0 > /sys/bus/pci/drivers_autoprobe > > # echo 2 > /sys/bus/pci/devices/DDDD:BB:dd.f/sriov_numvfs > > # echo 1 > /sys/bus/pci/drivers_autoprobe > > > >If not, can you contrast the above with drivers_autoprobe? If we need > >both, should they be named more similarly? > Hi Bjorn, > > I agree with Alex about not using driver_autoprobe to achieve this. > It will affect all pci related device once it's disabled(probably in > a bad way). I agree drivers_autoprobe is racy with respect to other PCI devices, so it's not a great solution to your issue. But I do want to make it obvious that these are related concepts. Alex mooted the idea of a generic driver core knob for devices that create child devices. That's intriguing. What other situations besides SR-IOV do this? Maybe we could add a "drivers_autoprobe" inside the directory of each device that's capable of having child devices? If we continue with the current approach (instead of Alex's idea), I propose that you: - Name your new knob "sriov_drivers_autoprobe" to be consistent with other sriov sysfs files while also being parallel to "drivers_autoprobe" - Update Documentation/ABI/testing/sysfs-bus-pci to document your new knob - Update Documentation/ABI/... to document drivers_autoprobe Bjorn