From patchwork Tue Apr 3 17:53:11 2018 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Bjorn Helgaas X-Patchwork-Id: 10321601 X-Patchwork-Delegate: bhelgaas@google.com Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork.web.codeaurora.org (Postfix) with ESMTP id 8EF8660318 for ; Tue, 3 Apr 2018 17:53:17 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 7DD0128BF6 for ; Tue, 3 Apr 2018 17:53:17 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id 7227628C84; Tue, 3 Apr 2018 17:53:17 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-6.9 required=2.0 tests=BAYES_00,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id D7E9028C82 for ; Tue, 3 Apr 2018 17:53:16 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751749AbeDCRxP (ORCPT ); Tue, 3 Apr 2018 13:53:15 -0400 Received: from mail.kernel.org ([198.145.29.99]:56912 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751638AbeDCRxN (ORCPT ); Tue, 3 Apr 2018 13:53:13 -0400 Received: from localhost (50-81-23-81.client.mchsi.com [50.81.23.81]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPSA id B17EC21720; Tue, 3 Apr 2018 17:53:12 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org B17EC21720 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=helgaas@kernel.org Date: Tue, 3 Apr 2018 12:53:11 -0500 From: Bjorn Helgaas To: John Garry Cc: Thierry Reding , mika.westerberg@linux.intel.com, rafael@kernel.org, lorenzo.pieralisi@arm.com, rjw@rjwysocki.net, hanjun.guo@linaro.org, robh+dt@kernel.org, bhelgaas@google.com, arnd@arndb.de, mark.rutland@arm.com, olof@lixom.net, dann.frazier@canonical.com, andy.shevchenko@gmail.com, robh@kernel.org, andriy.shevchenko@linux.intel.com, joe@perches.com, benh@kernel.crashing.org, linux-pci@vger.kernel.org, linux-kernel@vger.kernel.org, linux-acpi@vger.kernel.org, linuxarm@huawei.com, minyard@acm.org, devicetree@vger.kernel.org, linux-arch@vger.kernel.org, rdunlap@infradead.org, gregkh@linuxfoundation.org, akpm@linux-foundation.org, frowand.list@gmail.com, agraf@suse.de, linux-tegra@vger.kernel.org Subject: Re: [PATCH v17 01/10] LIB: Introduce a generic PIO mapping method Message-ID: <20180403175311.GD60020@bhelgaas-glaptop.roam.corp.google.com> References: <1521051359-34473-1-git-send-email-john.garry@huawei.com> <1521051359-34473-2-git-send-email-john.garry@huawei.com> <20180403140410.GE27789@ulmo> <20180403143909.GA21171@ulmo> <20180403163700.GA10059@ulmo> <19c46196-304a-1574-89c9-01c71d123539@huawei.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <19c46196-304a-1574-89c9-01c71d123539@huawei.com> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-pci-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-pci@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP On Tue, Apr 03, 2018 at 06:02:43PM +0100, John Garry wrote: > On 03/04/2018 17:37, Thierry Reding wrote: > > On Tue, Apr 03, 2018 at 05:01:37PM +0100, John Garry wrote: > > > > > > +int logic_pio_register_range(struct logic_pio_hwaddr *new_range) > > > > > > +{ > > > > > > + struct logic_pio_hwaddr *range; > > > > > > + resource_size_t start = new_range->hw_start; > > > > > > + resource_size_t end = new_range->hw_start + new_range->size; > > > > > > + resource_size_t mmio_sz = 0; > > > > > > + resource_size_t iio_sz = MMIO_UPPER_LIMIT; > > > > > > + int ret = 0; > > > > > > + > > > > > > + if (!new_range || !new_range->fwnode || !new_range->size) > > > > > > + return -EINVAL; > > > > > > + > > > > > > + mutex_lock(&io_range_mutex); > > > > > > + list_for_each_entry_rcu(range, &io_range_list, list) { > > > > > > + if (range->fwnode == new_range->fwnode) { > > > > > > + /* range already there */ > > > > > > + ret = -EFAULT; > > > > > > + goto end_register; > > > > > > + } > > > > > > > > > > > Hi Thierry, > > > > > > > > This is the -EFAULT that propagates to pci-tegra.c's ->probe() and fails > > > > > to bind the driver. > > > > > > > > > > I'm not exactly sure what's causing the duplicate here because it's > > > > > rather difficult to get at something useful from just the ->fwnode, but > > > > > I'm fairly sure that the reason this breaks is because the Tegra driver > > > > > will defer probe due to some regulators that aren't available on the > > > > > first try. Given the above code and the rest of this file, I can't see a > > > > > way to "fix" the driver and remove the I/O range on failure. > > > > > > > > > > This is doubly bad because this doesn't only leak the ranges on probe > > > > > deferral, but also on driver unload, and we just added support for > > > > > building the Tegra driver as a loadable module, so these are actually > > > > > cases that can happen in regular uses of the driver. > > > > > > > > > > I have no idea on how to fix this. Anyone know of a quick fix to restore > > > > > PCI for Tegra other than reverting all of these changes? > > > > > > > > > > I suppose an API could be added to unregister the range, but the calling > > > > > sequence is rather obfuscated, so removing the range will look totally > > > > > asymmetric, I'm afraid. > > > > > > > > > > Here's the call stack: > > > > > > > > > > tegra_pcie_probe() > > > > > tegra_pcie_parse_dt() > > > > > of_pci_range_to_resource() > > > > > pci_register_io_range() > > > > > logic_pio_register_range() > > > > > > > > > > So the range here is registered as part of a resource parsing function, > > > > > which is supposed to not have any side-effects. There's no equivalent of > > > > > that parsing routine (i.e. no "unparse" function that would undo the > > > > > effects of parsing). > > > > > > > > > > Perhaps a cleaner way would be to decouple the parsing from the actual > > > > > request step that has the side-effect. > > > > > > This could be added if we agreed that it would be useful. > > > > I guess in most cases these ranges will be static at least during one > > boot. But it still feels like this should be removed when the driver > > goes away. While this may not depend on data by the driver, and hence > > won't cause a crash or anything, it just seems wrong to leave it > > around when the driver no longer isn't. > > That sounds reasonable, considering we do unmap the iospace when we release > - so it looks like currently we're leaving some IO range reserved which does > not have a mapping. > > However this change seems non-trivial, considering we're now even coupling > the PIO range registration into DT parsing. > > > > > > > > Going back in history a little, it looks like even before this commit > > > > > the I/O range registration was triggered by the parsing code and even > > > > > the range leak was there, except that it caused pci_register_io_range() > > > > > to return 0 rather than -EFAULT. Perhaps the quickest fix for this would > > > > > be to do the same in the new code and restore drivers that accidentally > > > > > depend on this behaviour. > > > > > > > > I can confirm that the following fixes the issue for me, though I don't > > > > think it's a very clean fix given that the range will remain requested > > > > forever, even if the driver is gone. But since that's already been the > > > > case for quite a while, probably something that can be fixed separately. > > > > > > > > > > Right, there was no way to deregister the range previously. From looking at > > > the history here I see no reason to not support it. > > > > > > As for this patch, as you said, the only difference is that we fault on > > > trying to register the same range again. So this solution seems reasonable. > > > > Okay, I can turn this into a proper patch to fix this up. I suspect that > > other drivers may be subject to the same regression. For the longer term > > I think it'd be better to properly undo the registration on failure and > > removal, but I suspect that it'd be quite a bit of work and not suitable > > for v4.17 anymore. > > Thanks, I had started to put the patch together but if you're happy to > continue then that's fine. Please let me know. Since you seem to agree this is the right short-term fix and I would squash it into the original commit anyway, I went ahead and did that so we could get this into linux-next as soon as possible. Here's the diff from my previous "next" branch with respect to this series: diff --git a/lib/logic_pio.c b/lib/logic_pio.c index 29cedeadb397..4664b87e1c5f 100644 --- a/lib/logic_pio.c +++ b/lib/logic_pio.c @@ -46,7 +46,6 @@ int logic_pio_register_range(struct logic_pio_hwaddr *new_range) list_for_each_entry_rcu(range, &io_range_list, list) { if (range->fwnode == new_range->fwnode) { /* range already there */ - ret = -EFAULT; goto end_register; } if (range->flags == LOGIC_PIO_CPU_MMIO &&