[RFC PATCH v2, part 2 16/18] PCI, iommu: use hotplug-safe iterators to walk PCI buses

[Jiang Liu <liuj97-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>]

Enhance iommu drviers to use hotplug-safe iterators to walk
PCI buses.

Signed-off-by: Jiang Liu <jiang.liu-hv44wF8Li93QT0dZR+AlfA@public.gmane.org>
Cc: Joerg Roedel <joro-zLv9SwRftAIdnm+yROfE0A@public.gmane.org>
Cc: Ingo Molnar <mingo-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
Cc: Donald Dutile <ddutile-H+wXaHxf7aLQT0dZR+AlfA@public.gmane.org>
Cc: Hannes Reinecke <hare-l3A5Bk7waGM@public.gmane.org>
Cc: "Li, Zhen-Hua" <zhen-hual-VXdhtT5mjnY@public.gmane.org>
Cc: iommu-cunTk1MwBs9QetFLy7KEm3xJsTq8ys+cHZ5vskTnxNA@public.gmane.org
Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
---
 drivers/iommu/amd_iommu.c | 4 +++-
 drivers/iommu/dmar.c      | 6 ++++--
 2 files changed, 7 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index e046d7a..d6fdf94 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -357,6 +357,7 @@ static int init_iommu_group(struct device *dev)
 	struct iommu_dev_data *dev_data;
 	struct iommu_group *group;
 	struct pci_dev *dma_pdev;
+	struct pci_bus *b = NULL;
 	int ret;
 
 	group = iommu_group_get(dev);
@@ -393,7 +394,7 @@ static int init_iommu_group(struct device *dev)
 		 * the alias.  Be careful to also test the parent device if
 		 * we think the alias is the root of the group.
 		 */
-		bus = pci_find_bus(0, alias >> 8);
+		b = bus = pci_find_bus(0, alias >> 8);
 		if (!bus)
 			goto use_group;
 
@@ -413,6 +414,7 @@ static int init_iommu_group(struct device *dev)
 	dma_pdev = get_isolation_root(pci_dev_get(to_pci_dev(dev)));
 use_pdev:
 	ret = use_pdev_iommu_group(dma_pdev, dev);
+	pci_bus_put(b);
 	pci_dev_put(dma_pdev);
 	return ret;
 use_group:
diff --git a/drivers/iommu/dmar.c b/drivers/iommu/dmar.c
index e5cdaf8..5bb3cdc 100644
--- a/drivers/iommu/dmar.c
+++ b/drivers/iommu/dmar.c
@@ -67,12 +67,12 @@ static void __init dmar_register_drhd_unit(struct dmar_drhd_unit *drhd)
 static int __init dmar_parse_one_dev_scope(struct acpi_dmar_device_scope *scope,
 					   struct pci_dev **dev, u16 segment)
 {
-	struct pci_bus *bus;
+	struct pci_bus *b, *bus;
 	struct pci_dev *pdev = NULL;
 	struct acpi_dmar_pci_path *path;
 	int count;
 
-	bus = pci_find_bus(segment, scope->bus);
+	b = bus = pci_find_bus(segment, scope->bus);
 	path = (struct acpi_dmar_pci_path *)(scope + 1);
 	count = (scope->length - sizeof(struct acpi_dmar_device_scope))
 		/ sizeof(struct acpi_dmar_pci_path);
@@ -97,6 +97,8 @@ static int __init dmar_parse_one_dev_scope(struct acpi_dmar_device_scope *scope,
 		count --;
 		bus = pdev->subordinate;
 	}
+	pci_bus_put(b);
+
 	if (!pdev) {
 		pr_warn("Device scope device [%04x:%02x:%02x.%02x] not found\n",
 			segment, scope->bus, path->dev, path->fn);
-- 
1.8.1.2