[PATCH 3.16 011/136] iommu/vt-d: Don't register bus-notifier under dmar_global_lock

[Ben Hutchings]

3.16.54-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Joerg Roedel <jroedel@xxxxxxx>

commit ec154bf56b276a0bb36079a5d22a267b5f417801 upstream.

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 <jan.kiszka@xxxxxxxxxxx>
Fixes: 59ce0515cdaf ('iommu/vt-d: Update DRHD/RMRR/ATSR device scope caches when PCI hotplug happens')
Signed-off-by: Joerg Roedel <jroedel@xxxxxxx>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@xxxxxxxxxxxxxxx>
---
 drivers/iommu/dmar.c        |  7 +++++--
 drivers/iommu/intel-iommu.c | 10 ++++++++++
 include/linux/dmar.h        |  1 +
 3 files changed, 16 insertions(+), 2 deletions(-)

--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -718,13 +718,16 @@ 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)
 {
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4044,6 +4044,16 @@ 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)
 		goto out_free_dmar;
 
--- a/include/linux/dmar.h
+++ b/include/linux/dmar.h
@@ -100,6 +100,7 @@ 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);