[PATCH 4/5] iommu: Make sure a device is always attached to a domain

[Joerg Roedel <joro@8bytes.org>]

From: Joerg Roedel <jroedel@suse.de>

Make use of the default domain and re-attach a device to it
when it is detached from another domain. Also enforce that a
device has to be in the default domain before it can be
attached to a different domain.

Signed-off-by: Joerg Roedel <jroedel@suse.de>
---
 drivers/iommu/iommu.c | 34 +++++++++++++++++++++++++++++++---
 1 file changed, 31 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index b63a550..5080759 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -53,6 +53,7 @@ struct iommu_group {
 	int id;
 	unsigned dev_cnt;
 	struct iommu_domain *default_domain;
+	struct iommu_domain *domain;
 };
 
 struct iommu_device {
@@ -1040,8 +1041,17 @@ static int iommu_group_do_attach_device(struct device *dev, void *data)
 
 int iommu_attach_group(struct iommu_domain *domain, struct iommu_group *group)
 {
-	return iommu_group_for_each_dev(group, domain,
-					iommu_group_do_attach_device);
+	int ret;
+
+	if (group->default_domain && group->domain != group->default_domain)
+		return -EBUSY;
+
+	ret = iommu_group_for_each_dev(group, domain,
+				       iommu_group_do_attach_device);
+	if (ret == 0)
+		group->domain = domain;
+
+	return ret;
 }
 EXPORT_SYMBOL_GPL(iommu_attach_group);
 
@@ -1056,7 +1066,25 @@ static int iommu_group_do_detach_device(struct device *dev, void *data)
 
 void iommu_detach_group(struct iommu_domain *domain, struct iommu_group *group)
 {
-	iommu_group_for_each_dev(group, domain, iommu_group_do_detach_device);
+	int ret;
+
+	if (!group->default_domain) {
+		iommu_group_for_each_dev(group, domain,
+					 iommu_group_do_detach_device);
+		group->domain = NULL;
+		return;
+	}
+
+	if (group->domain == group->default_domain)
+		return;
+
+	/* Detach by re-attaching to the default domain */
+	ret = iommu_group_for_each_dev(group, group->default_domain,
+				       iommu_group_do_attach_device);
+	if (ret != 0)
+		WARN_ON(1);
+	else
+		group->domain = group->default_domain;
 }
 EXPORT_SYMBOL_GPL(iommu_detach_group);
 
-- 
1.9.1