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Subject[PATCH 3.16 011/136] iommu/vt-d: Don't register bus-notifier under dmar_global_lock
3.16.54-rc1 review patch.  If anyone has any objections, please let me know.

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

From: Joerg Roedel <jroedel@suse.de>

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@siemens.com>
Fixes: 59ce0515cdaf ('iommu/vt-d: Update DRHD/RMRR/ATSR device scope caches when PCI hotplug happens')
Signed-off-by: Joerg Roedel <jroedel@suse.de>
[bwh: Backported to 3.16: adjust context]
Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
---
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);
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