From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754955AbdJIQ6W (ORCPT ); Mon, 9 Oct 2017 12:58:22 -0400 Received: from david.siemens.de ([192.35.17.14]:37100 "EHLO david.siemens.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754255AbdJIQ6U (ORCPT ); Mon, 9 Oct 2017 12:58:20 -0400 Subject: Re: [PATCH] iommu/vt-d: Don't register bus-notifier under To: Joerg Roedel Cc: iommu@lists.linux-foundation.org, Linux Kernel Mailing List References: <4e9f9665-38f7-c5f0-2a9d-13bb3a00aab2@siemens.com> <6ed4183a-b2eb-b8d3-c54c-fb0c4fd7a813@siemens.com> <82afec06-4eb9-7b91-7b19-c442b77b5769@siemens.com> <20171006130823.a4rtzhusjpbgo3ar@suse.de> From: Jan Kiszka Message-ID: <2ee59dfe-0a02-05b6-8115-5846b49bc053@siemens.com> Date: Mon, 9 Oct 2017 18:58:13 +0200 User-Agent: Mozilla/5.0 (X11; U; Linux i686 (x86_64); de; rv:1.8.1.12) Gecko/20080226 SUSE/2.0.0.12-1.1 Thunderbird/2.0.0.12 Mnenhy/0.7.5.666 MIME-Version: 1.0 In-Reply-To: <20171006130823.a4rtzhusjpbgo3ar@suse.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 2017-10-06 15:08, Joerg Roedel wrote: > Hey Jan, > > On Wed, Sep 27, 2017 at 04:19:15PM +0200, Jan Kiszka wrote: >> If we could drop the dmar_global_lock around bus_register_notifier in >> dmar_dev_scope_init, the issue above would likely be resolved. > > That is true. Can you please try this patch? > >>>From dd7685f84d3954f9361bfb4290fb8a0dd033097a Mon Sep 17 00:00:00 2001 > From: Joerg Roedel > Date: Fri, 6 Oct 2017 15:00:53 +0200 > Subject: [PATCH] iommu/vt-d: Don't register bus-notifier under > dmar_global_lock > > The notifier function will take the dmar_global_lock too, so > lockdep complains about inverse locking order when the > notifier is registered under the dmar_global_lock. > > Reported-by: Jan Kiszka > Fixes: 59ce0515cdaf ('iommu/vt-d: Update DRHD/RMRR/ATSR device scope caches when PCI hotplug happens') > Signed-off-by: Joerg Roedel > --- > drivers/iommu/dmar.c | 7 +++++-- > drivers/iommu/intel-iommu.c | 10 ++++++++++ > include/linux/dmar.h | 1 + > 3 files changed, 16 insertions(+), 2 deletions(-) > > diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c > index 57c920c1372d..1ea7cd537873 100644 > --- a/drivers/iommu/dmar.c > +++ b/drivers/iommu/dmar.c > @@ -801,13 +801,16 @@ int __init dmar_dev_scope_init(void) > dmar_free_pci_notify_info(info); > } > } > - > - bus_register_notifier(&pci_bus_type, &dmar_pci_bus_nb); > } > > return dmar_dev_scope_status; > } > > +void dmar_register_bus_notifier(void) > +{ > + bus_register_notifier(&pci_bus_type, &dmar_pci_bus_nb); > +} > + > > int __init dmar_table_init(void) > { > diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c > index 6784a05dd6b2..934cef924461 100644 > --- a/drivers/iommu/intel-iommu.c > +++ b/drivers/iommu/intel-iommu.c > @@ -4752,6 +4752,16 @@ int __init intel_iommu_init(void) > goto out_free_dmar; > } > > + up_write(&dmar_global_lock); > + > + /* > + * The bus notifier takes the dmar_global_lock, so lockdep will > + * complain later when we register it under the lock. > + */ > + dmar_register_bus_notifier(); > + > + down_write(&dmar_global_lock); > + > if (no_iommu || dmar_disabled) { > /* > * We exit the function here to ensure IOMMU's remapping and > diff --git a/include/linux/dmar.h b/include/linux/dmar.h > index e8ffba1052d3..e2433bc50210 100644 > --- a/include/linux/dmar.h > +++ b/include/linux/dmar.h > @@ -112,6 +112,7 @@ static inline bool dmar_rcu_check(void) > > extern int dmar_table_init(void); > extern int dmar_dev_scope_init(void); > +extern void dmar_register_bus_notifier(void); > extern int dmar_parse_dev_scope(void *start, void *end, int *cnt, > struct dmar_dev_scope **devices, u16 segment); > extern void *dmar_alloc_dev_scope(void *start, void *end, int *cnt); > Silences the warning, but locking in the init paths still smells fishy to me. Thanks, Jan -- Siemens AG, Corporate Technology, CT RDA ITP SES-DE Corporate Competence Center Embedded Linux