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=-8.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_PATCH,MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 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 A91DEC47E49 for ; Wed, 23 Oct 2019 09:39:37 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8843D21D7B for ; Wed, 23 Oct 2019 09:39:37 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2403918AbfJWJjg (ORCPT ); Wed, 23 Oct 2019 05:39:36 -0400 Received: from mga05.intel.com ([192.55.52.43]:55175 "EHLO mga05.intel.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390380AbfJWJjg (ORCPT ); Wed, 23 Oct 2019 05:39:36 -0400 X-Amp-Result: UNKNOWN X-Amp-Original-Verdict: FILE UNKNOWN X-Amp-File-Uploaded: False Received: from fmsmga001.fm.intel.com ([10.253.24.23]) by fmsmga105.fm.intel.com with ESMTP/TLS/DHE-RSA-AES256-GCM-SHA384; 23 Oct 2019 02:39:35 -0700 X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="5.68,220,1569308400"; d="scan'208";a="209888327" Received: from lahna.fi.intel.com (HELO lahna) ([10.237.72.157]) by fmsmga001.fm.intel.com with SMTP; 23 Oct 2019 02:39:32 -0700 Received: by lahna (sSMTP sendmail emulation); Wed, 23 Oct 2019 12:39:32 +0300 Date: Wed, 23 Oct 2019 12:39:32 +0300 From: "mika.westerberg@linux.intel.com" To: Nicholas Johnson Cc: "linux-kernel@vger.kernel.org" , "linux-pci@vger.kernel.org" , "bhelgaas@google.com" , "corbet@lwn.net" , "benh@kernel.crashing.org" , "logang@deltatee.com" Subject: Re: [PATCH v8 4/6] PCI: Allow extend_bridge_window() to shrink resource if necessary Message-ID: <20191023093932.GS2819@lahna.fi.intel.com> References: <20191008120907.GI2819@lahna.fi.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Organization: Intel Finland Oy - BIC 0357606-4 - Westendinkatu 7, 02160 Espoo User-Agent: Mutt/1.12.1 (2019-06-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, Oct 23, 2019 at 09:16:10AM +0000, Nicholas Johnson wrote: > On Tue, Oct 08, 2019 at 03:09:07PM +0300, mika.westerberg@linux.intel.com wrote: > > On Fri, Jul 26, 2019 at 12:54:22PM +0000, Nicholas Johnson wrote: > > > Remove checks for resource size in extend_bridge_window(). This is > > > necessary to allow the pci_bus_distribute_available_resources() to > > > function when the kernel parameter pci=hpmemsize=nn[KMG] is used to > > > allocate resources. Because the kernel parameter sets the size of all > > > hotplug bridges to be the same, there are problems when nested hotplug > > > bridges are encountered. Fitting a downstream hotplug bridge with size X > > > and normal bridges with size Y into parent hotplug bridge with size X is > > > impossible, and hence the downstream hotplug bridge needs to shrink to > > > fit into its parent. > > > > Maybe you could show the topology here which needs shrinking. > > > > > Add check for if bridge is extended or shrunken and adjust pci_dbg to > > > reflect this. > > > > > > Reset the resource if its new size is zero (if we have run out of a > > > bridge window resource). If it is set to zero size and left, it can > > > cause significant problems when it comes to enabling devices. > > > > Same comment here about explaining the "significant problems". > I have in the past, but because the problems are very hard to describe succinctly, it just turns into a > nightmare. I can try to do it again. > > > > > > > Signed-off-by: Nicholas Johnson > > > --- > > > drivers/pci/setup-bus.c | 16 +++++++++++----- > > > 1 file changed, 11 insertions(+), 5 deletions(-) > > > > > > diff --git a/drivers/pci/setup-bus.c b/drivers/pci/setup-bus.c > > > index a072781ab..7e1dc892a 100644 > > > --- a/drivers/pci/setup-bus.c > > > +++ b/drivers/pci/setup-bus.c > > > @@ -1823,13 +1823,19 @@ static void extend_bridge_window(struct pci_dev *bridge, struct resource *res, > > > > Since it is also shrinking now maybe name it adjust_bridge_window() instead? > I am happy to do this. > > If we can drop the pci_dbg() calls, then I might be able to drop this > function entirely. During the development of this patch, that is exactly > what I did. How important are the pci_dbg calls to you? Well they are still useful when debugging resource allocation issues (and they match similar we do when extending number of buses). I would like to keep them if possible.