From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mga01.intel.com ([192.55.52.88]:44745 "EHLO mga01.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753637Ab2GPRzH (ORCPT ); Mon, 16 Jul 2012 13:55:07 -0400 Date: Mon, 16 Jul 2012 10:55:06 -0700 From: Jon Mason To: Greg KH Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org, linux-pci@vger.kernel.org, Dave Jiang Subject: Re: [RFC 1/2] PCI-Express Non-Transparent Bridge Support Message-ID: <20120716175505.GF9598@jonmason-lab> References: <1342215900-3358-1-git-send-email-jon.mason@intel.com> <20120714171015.GB25775@kroah.com> <20120715235548.GC7551@jonmason-lab> <20120716001921.GA19775@kroah.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii In-Reply-To: <20120716001921.GA19775@kroah.com> Sender: linux-pci-owner@vger.kernel.org List-ID: On Sun, Jul 15, 2012 at 05:19:21PM -0700, Greg KH wrote: > On Sun, Jul 15, 2012 at 04:55:48PM -0700, Jon Mason wrote: > > On Sat, Jul 14, 2012 at 10:10:15AM -0700, Greg KH wrote: > > > On Fri, Jul 13, 2012 at 02:44:59PM -0700, Jon Mason wrote: > > > > +static int max_num_cbs = 2; > > > > +module_param(max_num_cbs, uint, 0644); > > > > +MODULE_PARM_DESC(max_num_cbs, "Maximum number of NTB transport connections"); > > > > + > > > > +static bool no_msix; > > > > +module_param(no_msix, bool, 0644); > > > > +MODULE_PARM_DESC(no_msix, "Do not allow MSI-X interrupts to be selected"); > > > > > > How would a user, or a distro, know to set these options? Why are they > > > even options at all? > > > > Good question. There is actually a potential benefit to disabling > > MSI-X. The NTB device on one of our platforms only has 3 MSI-X > > vectors. In the current driver design, that would limit them to 3 > > client/virtual devices. However, there are 15bits in the ISR that can > > be used for the same purpose. So, if you disable MSI-X, you can have > > 15 instead of 3. > > But again, how would a user, or a distro, know to set these? Where is > the documentation describing it? Why really have these options at all > and not just fix the platform issues (only 3 MSI-X vectors? Really?) I believe we'll want multiple clients (or have multiqueue Ethernet). I'm happy to add something to /Documentation to describe it and why it would be useful, or I can remove it and re-introduce it when I add multiqueue Ethernet. 3 MSI-X vectors (plus one for PCI-E link up/down) on Xeon NTB, and 33 for Atom NTB. Yeah, really. > > thanks, > > greg k-h