Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751294AbdCOCzz (ORCPT ); Tue, 14 Mar 2017 22:55:55 -0400 Received: from mail.kernel.org ([198.145.29.136]:60188 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750797AbdCOCzy (ORCPT ); Tue, 14 Mar 2017 22:55:54 -0400 Date: Tue, 14 Mar 2017 21:55:49 -0500 From: Bjorn Helgaas To: Andi Kleen Cc: Thomas Gleixner , Andi Kleen , bhelgaas@google.com, x86@kernel.org, linux-pci@vger.kernel.org, eranian@google.com, Peter Zijlstra , LKML Subject: Re: [PATCH 3/4] x86, pci: Add interface to force mmconfig Message-ID: <20170315025549.GA13191@bhelgaas-glaptop.roam.corp.google.com> References: <20170302232104.10136-1-andi@firstfloor.org> <20170302232104.10136-3-andi@firstfloor.org> <20170314154155.GG32070@tassilo.jf.intel.com> <20170314170255.GH32070@tassilo.jf.intel.com> <20170314194720.GD26264@bhelgaas-glaptop.roam.corp.google.com> <20170315022414.GC14380@two.firstfloor.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170315022414.GC14380@two.firstfloor.org> 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: 1067 Lines: 28 On Tue, Mar 14, 2017 at 07:24:14PM -0700, Andi Kleen wrote: > > I agree that it should be fairly safe to do ECAM/MMCONFIG without > > locking. Can we handle the decision part by adding a "lockless" bit > > to struct pci_ops? Old ops don't mention that bit, so it will be > > initialized to zero and we'll do locking as today. ECAM/MMCONFIG ops > > can set it and we can skip the locking. > > That's what my other patch already did. Yes, your 1/4 patch does add the "ll_allowed" bit in struct pci_ops. What I was wondering, but didn't explain very well, was whether instead of setting that bit at run-time in pci_mmcfg_arch_init(), we could set it statically in the pci_ops definition, e.g., static struct pci_ops ecam_ops = { .lockless = 1, .read = ecam_read, .write = ecam_write, }; I think it would be easier to read if the lockless-ness were declared right next to the accessors that need it (or don't need it). But it is a little confusing with all the different paths, at least on x86, so maybe it wouldn't be quite that simple. Bjorn