[Qemu-devel] [RFC PATCH 0/3] IOMMU groups

[Qemu-devel] [RFC PATCH 0/3] IOMMU groups

[Alex Williamson]

This series attempts to make IOMMU device grouping a slightly more
integral part of the device model.  iommu_device_groups were originally
introduced to support the VFIO user space driver interface which needs
to understand the granularity of device isolation in order to ensure
security of devices when assigned for user access.  This information
was provided via a simple group identifier from the IOMMU driver allowing
VFIO to walk devices and assemble groups itself.

The feedback received from this was that groups should be the effective
unit of work for the IOMMU API.  The existing model of allowing domains
to be created and individual devices attached ignores many of the
restrictions of the IOMMU, whether by design, by topology or by defective
devices.  Additionally we should be able to use the grouping information
at the dma ops layer for managing domains and quirking devices.

This series is a sketch at implementing only those aspects and leaving
everything else about the multifaceted hairball of Isolation groups for
another API.  Please comment and let me know if this seems like the
direction we should be headed.  Thanks,

Alex


---

Alex Williamson (3):
      iommu: Create attach/detach group interface
      iommu: Create basic group infrastructure and update AMD-Vi & Intel VT-d
      iommu: Introduce iommu_group


 drivers/iommu/amd_iommu.c   |   50 ++++++----
 drivers/iommu/intel-iommu.c |   76 ++++++++--------
 drivers/iommu/iommu.c       |  210 ++++++++++++++++++++++++++++++++++++++-----
 include/linux/device.h      |    2 
 include/linux/iommu.h       |   43 +++++++++
 5 files changed, 301 insertions(+), 80 deletions(-)

[Qemu-devel] [RFC PATCH 1/3] iommu: Introduce iommu_group

[Alex Williamson]

IOMMUs often do not have visibility of individual devices in the
system.  Due to IOMMU design, bus topology, or device quirks, we
can often only identify groups of devices.  Examples include
Intel VT-d & AMD-Vi which often have function level visibility
compared to POWER partitionable endpoints which have bridge level
granularity.  PCIe-to-PCI bridges also often cloud the IOMMU
visibility as it cannot distiguish devices behind the bridge.
Devices can also sometimes hurt themselves by initiating DMA using
the wrong source ID on a multifunction PCI device.

IOMMU groups are meant to help solve these problems and hopefully
become the working unit of the IOMMI API.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

 include/linux/device.h |    2 ++
 include/linux/iommu.h  |    5 +++++
 2 files changed, 7 insertions(+), 0 deletions(-)

diff --git a/include/linux/device.h b/include/linux/device.h
index b63fb39..6acab1c 100644
--- a/include/linux/device.h
+++ b/include/linux/device.h
@@ -35,6 +35,7 @@ struct subsys_private;
 struct bus_type;
 struct device_node;
 struct iommu_ops;
+struct iommu_group;
 
 struct bus_attribute {
 	struct attribute	attr;
@@ -683,6 +684,7 @@ struct device {
 	const struct attribute_group **groups;	/* optional groups */
 
 	void	(*release)(struct device *dev);
+	struct iommu_group	*iommu_group;
 };
 
 /* Get the wakeup routines, which depend on struct device */
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index d937580..2ee375c 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -26,6 +26,7 @@
 #define IOMMU_CACHE	(4) /* DMA cache coherency */
 
 struct iommu_ops;
+struct iommu_group;
 struct bus_type;
 struct device;
 struct iommu_domain;
@@ -78,6 +79,9 @@ struct iommu_ops {
 	unsigned long pgsize_bitmap;
 };
 
+struct iommu_group {
+};
+
 extern int bus_set_iommu(struct bus_type *bus, struct iommu_ops *ops);
 extern bool iommu_present(struct bus_type *bus);
 extern struct iommu_domain *iommu_domain_alloc(struct bus_type *bus);
@@ -140,6 +144,7 @@ static inline int report_iommu_fault(struct iommu_domain *domain,
 #else /* CONFIG_IOMMU_API */
 
 struct iommu_ops {};
+struct iommu_group {};
 
 static inline bool iommu_present(struct bus_type *bus)
 {

[Qemu-devel] [RFC PATCH 2/3] iommu: Create basic group infrastructure and update AMD-Vi & Intel VT-d

[Alex Williamson]

IOMMU groups define the minimum granularity of the IOMMU.  We therefore
create groups using a dma_dev which is the effective requestor ID for
the entire group.  Additional devices can be added to groups based on
system topology, IOMMU limitations, or device quirks.

This implementation also includes a simple idr database for creating
a flat address space of group IDs across multiple IOMMUs.  Updates
included for Intel VT-d, using example iommu callbacks for adding and
removing devices, as well as AMD-Vi, which tracks devices on it's own.
We should be able to better integrate the iommu_group within existing
AMD-Vi structs or provide a private data location within the iommu_group
where we can eventually reduce redundancy.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

 drivers/iommu/amd_iommu.c   |   50 ++++++-----
 drivers/iommu/intel-iommu.c |   76 +++++++++--------
 drivers/iommu/iommu.c       |  198 ++++++++++++++++++++++++++++++++++++++-----
 include/linux/iommu.h       |   23 +++++
 4 files changed, 267 insertions(+), 80 deletions(-)

diff --git a/drivers/iommu/amd_iommu.c b/drivers/iommu/amd_iommu.c
index f75e060..876db28 100644
--- a/drivers/iommu/amd_iommu.c
+++ b/drivers/iommu/amd_iommu.c
@@ -256,9 +256,10 @@ static bool check_device(struct device *dev)
 
 static int iommu_init_device(struct device *dev)
 {
-	struct pci_dev *pdev = to_pci_dev(dev);
+	struct pci_dev *dma_pdev, *pdev = to_pci_dev(dev);
 	struct iommu_dev_data *dev_data;
 	u16 alias;
+	int ret;
 
 	if (dev->archdata.iommu)
 		return 0;
@@ -279,6 +280,26 @@ static int iommu_init_device(struct device *dev)
 			return -ENOTSUPP;
 		}
 		dev_data->alias_data = alias_data;
+
+		dma_pdev = pci_get_bus_and_slot(alias >> 8, alias & 0xff);
+	} else
+		dma_pdev = pdev;
+
+	/* dma_pdev = iommu_pci_quirk(dma_pdev) */
+
+	if (!dma_pdev->dev.iommu_group) {
+		struct iommu_group *group;
+
+		group = iommu_group_alloc(&dma_pdev->dev);
+		if (IS_ERR(group))
+			return PTR_ERR(group);
+	}
+
+	ret = iommu_group_add_device(dma_pdev->dev.iommu_group, dev);
+	if (ret) {
+		if (iommu_group_empty(dma_pdev->dev.iommu_group))
+			iommu_group_free(dma_pdev->dev.iommu_group);
+		return ret;
 	}
 
 	if (pci_iommuv2_capable(pdev)) {
@@ -309,6 +330,12 @@ static void iommu_ignore_device(struct device *dev)
 
 static void iommu_uninit_device(struct device *dev)
 {
+	struct iommu_group *group = dev->iommu_group;
+
+	iommu_group_remove_device(dev);
+	if (iommu_group_empty(group))
+		iommu_group_free(group);
+
 	/*
 	 * Nothing to do here - we keep dev_data around for unplugged devices
 	 * and reuse it when the device is re-plugged - not doing so would
@@ -3191,26 +3218,6 @@ static int amd_iommu_domain_has_cap(struct iommu_domain *domain,
 	return 0;
 }
 
-static int amd_iommu_device_group(struct device *dev, unsigned int *groupid)
-{
-	struct iommu_dev_data *dev_data = dev->archdata.iommu;
-	struct pci_dev *pdev = to_pci_dev(dev);
-	u16 devid;
-
-	if (!dev_data)
-		return -ENODEV;
-
-	if (pdev->is_virtfn || !iommu_group_mf)
-		devid = dev_data->devid;
-	else
-		devid = calc_devid(pdev->bus->number,
-				   PCI_DEVFN(PCI_SLOT(pdev->devfn), 0));
-
-	*groupid = amd_iommu_alias_table[devid];
-
-	return 0;
-}
-
 static struct iommu_ops amd_iommu_ops = {
 	.domain_init = amd_iommu_domain_init,
 	.domain_destroy = amd_iommu_domain_destroy,
@@ -3220,7 +3227,6 @@ static struct iommu_ops amd_iommu_ops = {
 	.unmap = amd_iommu_unmap,
 	.iova_to_phys = amd_iommu_iova_to_phys,
 	.domain_has_cap = amd_iommu_domain_has_cap,
-	.device_group = amd_iommu_device_group,
 	.pgsize_bitmap	= AMD_IOMMU_PGSIZES,
 };
 
diff --git a/drivers/iommu/intel-iommu.c b/drivers/iommu/intel-iommu.c
index c9c6053..41ab7d0 100644
--- a/drivers/iommu/intel-iommu.c
+++ b/drivers/iommu/intel-iommu.c
@@ -4075,54 +4075,59 @@ static int intel_iommu_domain_has_cap(struct iommu_domain *domain,
 	return 0;
 }
 
-/*
- * Group numbers are arbitrary.  Device with the same group number
- * indicate the iommu cannot differentiate between them.  To avoid
- * tracking used groups we just use the seg|bus|devfn of the lowest
- * level we're able to differentiate devices
- */
-static int intel_iommu_device_group(struct device *dev, unsigned int *groupid)
+static int intel_iommu_add_device(struct device *dev)
 {
 	struct pci_dev *pdev = to_pci_dev(dev);
-	struct pci_dev *bridge;
-	union {
-		struct {
-			u8 devfn;
-			u8 bus;
-			u16 segment;
-		} pci;
-		u32 group;
-	} id;
-
-	if (iommu_no_mapping(dev))
-		return -ENODEV;
-
-	id.pci.segment = pci_domain_nr(pdev->bus);
-	id.pci.bus = pdev->bus->number;
-	id.pci.devfn = pdev->devfn;
+	struct pci_dev *bridge, *dma_pdev = pdev;
+	int ret;
 
-	if (!device_to_iommu(id.pci.segment, id.pci.bus, id.pci.devfn))
+	if (!device_to_iommu(pci_domain_nr(pdev->bus),
+			     pdev->bus->number, pdev->devfn))
 		return -ENODEV;
 
 	bridge = pci_find_upstream_pcie_bridge(pdev);
 	if (bridge) {
-		if (pci_is_pcie(bridge)) {
-			id.pci.bus = bridge->subordinate->number;
-			id.pci.devfn = 0;
-		} else {
-			id.pci.bus = bridge->bus->number;
-			id.pci.devfn = bridge->devfn;
-		}
+		if (pci_is_pcie(bridge))
+			dma_pdev = pci_get_domain_bus_and_slot(
+						pci_domain_nr(pdev->bus),
+						bridge->subordinate->number, 0);
+		else
+			dma_pdev = bridge;
+	}
+
+	if (!bridge && !pdev->is_virtfn && iommu_group_mf)
+		dma_pdev = pci_get_slot(dma_pdev->bus, 0);
+
+	/* dma_pdev = iommu_pci_quirk(dma_pdev); */
+
+	if (!dma_pdev->dev.iommu_group) {
+		struct iommu_group *group;
+
+		group = iommu_group_alloc(&dma_pdev->dev);
+		if (IS_ERR(group))
+			return PTR_ERR(group);
 	}
 
-	if (!pdev->is_virtfn && iommu_group_mf)
-		id.pci.devfn = PCI_DEVFN(PCI_SLOT(id.pci.devfn), 0);
+	ret = iommu_group_add_device(dma_pdev->dev.iommu_group, dev);
+	if (ret) {
+		if (iommu_group_empty(dma_pdev->dev.iommu_group))
+			iommu_group_free(dma_pdev->dev.iommu_group);
 
-	*groupid = id.group;
+		return ret;
+	}
 
 	return 0;
 }
 
+static void intel_iommu_remove_device(struct device *dev)
+{
+	struct iommu_group *group = dev->iommu_group;
+
+	iommu_group_remove_device(dev);
+	if (iommu_group_empty(group))
+		iommu_group_free(group);
+}
+
 static struct iommu_ops intel_iommu_ops = {
 	.domain_init	= intel_iommu_domain_init,
 	.domain_destroy = intel_iommu_domain_destroy,
@@ -4132,7 +4137,8 @@ static struct iommu_ops intel_iommu_ops = {
 	.unmap		= intel_iommu_unmap,
 	.iova_to_phys	= intel_iommu_iova_to_phys,
 	.domain_has_cap = intel_iommu_domain_has_cap,
-	.device_group	= intel_iommu_device_group,
+	.add_device	= intel_iommu_add_device,
+	.remove_device	= intel_iommu_remove_device,
 	.pgsize_bitmap	= INTEL_IOMMU_PGSIZES,
 };
 
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 2198b2d..6a51ed9 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -26,48 +26,96 @@
 #include <linux/slab.h>
 #include <linux/errno.h>
 #include <linux/iommu.h>
+#include <linux/idr.h>
 
-static ssize_t show_iommu_group(struct device *dev,
-				struct device_attribute *attr, char *buf)
+static struct kset *iommu_group_kset;
+static struct idr iommu_group_idr;
+static struct mutex iommu_group_mutex;
+
+struct iommu_group_attribute {
+	struct attribute attr;
+	ssize_t (*show)(struct iommu_group *group, char *buf);
+	ssize_t (*store)(struct iommu_group *group,
+			 const char *buf, size_t count);
+};
+
+#define to_iommu_group_attr(_attr)	\
+	container_of(_attr, struct iommu_group_attribute, attr)
+#define to_iommu_group(_kobj)		\
+	container_of(_kobj, struct iommu_group, kobj)
+
+static ssize_t iommu_group_attr_show(struct kobject *kobj,
+				     struct attribute *__attr, char *buf)
 {
-	unsigned int groupid;
+	struct iommu_group_attribute *attr = to_iommu_group_attr(__attr);
+	struct iommu_group *group = to_iommu_group(kobj);
+	ssize_t ret = -EIO;
 
-	if (iommu_device_group(dev, &groupid))
-		return 0;
+	if (attr->show)
+		ret = attr->show(group, buf);
+	return ret;
+}
+
+static ssize_t iommu_group_attr_store(struct kobject *kobj,
+				      struct attribute *__attr,
+				      const char *buf, size_t count)
+{
+	struct iommu_group_attribute *attr = to_iommu_group_attr(__attr);
+	struct iommu_group *group = to_iommu_group(kobj);
+	ssize_t ret = -EIO;
 
-	return sprintf(buf, "%u", groupid);
+	if (attr->store)
+		ret = attr->store(group, buf, count);
+	return ret;
 }
-static DEVICE_ATTR(iommu_group, S_IRUGO, show_iommu_group, NULL);
 
-static int add_iommu_group(struct device *dev, void *data)
+static void iommu_group_release(struct kobject *kobj)
 {
-	unsigned int groupid;
+	struct iommu_group *group = to_iommu_group(kobj);
 
-	if (iommu_device_group(dev, &groupid) == 0)
-		return device_create_file(dev, &dev_attr_iommu_group);
+	mutex_lock(&iommu_group_mutex);
+	idr_remove(&iommu_group_idr, group->id);
+	mutex_unlock(&iommu_group_mutex);
 
-	return 0;
+	kfree(group);
 }
 
-static int remove_iommu_group(struct device *dev)
+static const struct sysfs_ops iommu_group_sysfs_ops = {
+	.show = iommu_group_attr_show,
+	.store = iommu_group_attr_store,
+};
+
+static struct kobj_type iommu_group_ktype = {
+	.sysfs_ops = &iommu_group_sysfs_ops,
+	.release = iommu_group_release,
+};
+
+static int add_iommu_group(struct device *dev, void *data)
 {
-	unsigned int groupid;
+	struct iommu_ops *ops = data;
 
-	if (iommu_device_group(dev, &groupid) == 0)
-		device_remove_file(dev, &dev_attr_iommu_group);
+	if (!ops->add_device)
+		return -ENODEV;
 
-	return 0;
+	WARN_ON(dev->iommu_group);
+
+	return ops->add_device(dev);
 }
 
 static int iommu_device_notifier(struct notifier_block *nb,
 				 unsigned long action, void *data)
 {
 	struct device *dev = data;
+	struct iommu_ops *ops = dev->bus->iommu_ops;
 
 	if (action == BUS_NOTIFY_ADD_DEVICE)
-		return add_iommu_group(dev, NULL);
-	else if (action == BUS_NOTIFY_DEL_DEVICE)
-		return remove_iommu_group(dev);
+		return add_iommu_group(dev, ops);
+	else if (action == BUS_NOTIFY_DEL_DEVICE) {
+		if (ops->remove_device && dev->iommu_group) {
+			ops->remove_device(dev);
+			return 0;
+		}
+	}
 
 	return 0;
 }
@@ -79,7 +127,97 @@ static struct notifier_block iommu_device_nb = {
 static void iommu_bus_init(struct bus_type *bus, struct iommu_ops *ops)
 {
 	bus_register_notifier(bus, &iommu_device_nb);
-	bus_for_each_dev(bus, NULL, NULL, add_iommu_group);
+	bus_for_each_dev(bus, NULL, ops, add_iommu_group);
+}
+
+struct iommu_group *iommu_group_alloc(struct device *dma_dev)
+{
+	struct iommu_group *group;
+	int ret;
+
+	group = kzalloc(sizeof(*group), GFP_KERNEL);
+	if (!group)
+		return ERR_PTR(-ENOMEM);
+
+	group->kobj.kset = iommu_group_kset;
+	group->dma_dev = dma_dev;
+	atomic_set(&group->refcnt, 0);
+
+	mutex_lock(&iommu_group_mutex);
+
+again:
+	if (unlikely(0 == idr_pre_get(&iommu_group_idr, GFP_KERNEL))) {
+		kfree(group);
+		mutex_unlock(&iommu_group_mutex);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	if (-EAGAIN == idr_get_new(&iommu_group_idr, group, &group->id))
+		goto again;
+
+	mutex_unlock(&iommu_group_mutex);
+
+	ret = kobject_init_and_add(&group->kobj, &iommu_group_ktype,
+				   NULL, "%d", group->id);
+	if (ret) {
+		iommu_group_release(&group->kobj);
+		return ERR_PTR(ret);
+	}
+
+	group->devices_kobj = kobject_create_and_add("devices", &group->kobj);
+        if (!group->devices_kobj) {
+		kobject_put(&group->kobj);
+		return ERR_PTR(-ENOMEM);
+	}
+
+	dma_dev->iommu_group = group;
+
+	return group;
+}
+
+void iommu_group_free(struct iommu_group *group)
+{
+	group->dma_dev->iommu_group = NULL;
+	WARN_ON(atomic_read(&group->refcnt));
+	kobject_put(group->devices_kobj);
+	kobject_put(&group->kobj);
+}
+
+bool iommu_group_empty(struct iommu_group *group)
+{
+	return (0 == atomic_read(&group->refcnt));
+}
+
+int iommu_group_add_device(struct iommu_group *group, struct device *dev)
+{
+	int ret;
+
+	atomic_inc(&group->refcnt);
+
+	ret = sysfs_create_link(&dev->kobj, &group->kobj, "iommu_group");
+	if (ret)
+		return ret;
+
+	ret = sysfs_create_link(group->devices_kobj, &dev->kobj,
+                                kobject_name(&dev->kobj));
+	if (ret) {
+		sysfs_remove_link(&dev->kobj, "iommu_group");
+		return ret;
+	}
+
+	dev->iommu_group = group;
+
+	return 0;
+}
+
+void iommu_group_remove_device(struct device *dev)
+{
+	sysfs_remove_link(dev->iommu_group->devices_kobj,
+			  kobject_name(&dev->kobj));
+	sysfs_remove_link(&dev->kobj, "iommu_group");
+
+	atomic_dec(&dev->iommu_group->refcnt);
+	dev->iommu_group = NULL;
 }
 
 /**
@@ -335,9 +473,23 @@ EXPORT_SYMBOL_GPL(iommu_unmap);
 
 int iommu_device_group(struct device *dev, unsigned int *groupid)
 {
-	if (iommu_present(dev->bus) && dev->bus->iommu_ops->device_group)
-		return dev->bus->iommu_ops->device_group(dev, groupid);
+	if (dev->iommu_group) {
+		*groupid = dev->iommu_group->id;
+		return 0;
+	}
 
 	return -ENODEV;
 }
 EXPORT_SYMBOL_GPL(iommu_device_group);
+
+static int __init iommu_init(void)
+{
+	iommu_group_kset = kset_create_and_add("iommu_groups", NULL, NULL);
+	idr_init(&iommu_group_idr);
+	mutex_init(&iommu_group_mutex);
+
+	BUG_ON(!iommu_group_kset);
+
+	return 0;
+}
+subsys_initcall(iommu_init);
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 2ee375c..24004d6 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -60,6 +60,8 @@ struct iommu_domain {
  * @iova_to_phys: translate iova to physical address
  * @domain_has_cap: domain capabilities query
  * @commit: commit iommu domain
+ * @add_device: add device to iommu grouping
+ * @remove_device: remove device from iommu grouping
  * @pgsize_bitmap: bitmap of supported page sizes
  */
 struct iommu_ops {
@@ -76,10 +78,25 @@ struct iommu_ops {
 	int (*domain_has_cap)(struct iommu_domain *domain,
 			      unsigned long cap);
 	int (*device_group)(struct device *dev, unsigned int *groupid);
+	int (*add_device)(struct device *dev);
+	void (*remove_device)(struct device *dev);
 	unsigned long pgsize_bitmap;
 };
 
+/**
+ * struct iommu_group - groups of devices representing iommu visibility
+ * @dma_dev: all dma from the group appears to the iommu using this source id
+ * @kobj: iommu group node in sysfs
+ * @devices_kobj: sysfs subdir node for linking devices
+ * @refcnt: number of devices in group
+ * @id: unique id number for the group (for easy sysfs listing)
+ */
 struct iommu_group {
+	struct device *dma_dev;
+	struct kobject kobj;
+	struct kobject *devices_kobj;
+	atomic_t refcnt;
+	int id;
 };
 
 extern int bus_set_iommu(struct bus_type *bus, struct iommu_ops *ops);
@@ -101,6 +118,12 @@ extern int iommu_domain_has_cap(struct iommu_domain *domain,
 extern void iommu_set_fault_handler(struct iommu_domain *domain,
 					iommu_fault_handler_t handler);
 extern int iommu_device_group(struct device *dev, unsigned int *groupid);
+extern struct iommu_group *iommu_group_alloc(struct device *dev);
+extern void iommu_group_free(struct iommu_group *group);
+extern bool iommu_group_empty(struct iommu_group *group);
+extern int iommu_group_add_device(struct iommu_group *group,
+				  struct device *dev);
+extern void iommu_group_remove_device(struct device *dev);
 
 /**
  * report_iommu_fault() - report about an IOMMU fault to the IOMMU framework

[Qemu-devel] [RFC PATCH 3/3] iommu: Create attach/detach group interface

[Alex Williamson]

IOMMU ops should be working at a group level rather than a device
level as we cannot arbitrarily assign devices from the same group
to different domains.  For now this is just a simple wrapper that
makes use of the dma_dev within a group.

Signed-off-by: Alex Williamson <alex.williamson@redhat.com>
---

 drivers/iommu/iommu.c |   12 ++++++++++++
 include/linux/iommu.h |   15 +++++++++++++++
 2 files changed, 27 insertions(+), 0 deletions(-)

diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 6a51ed9..af77da1 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -327,6 +327,18 @@ void iommu_detach_device(struct iommu_domain *domain, struct device *dev)
 }
 EXPORT_SYMBOL_GPL(iommu_detach_device);
 
+int iommu_attach_group(struct iommu_domain *domain, struct iommu_group *group)
+{
+	return iommu_attach_device(domain, group->dma_dev);
+}
+EXPORT_SYMBOL_GPL(iommu_attach_group);
+
+void iommu_detach_group(struct iommu_domain *domain, struct iommu_group *group)
+{
+	iommu_detach_device(domain, group->dma_dev);
+}
+EXPORT_SYMBOL_GPL(iommu_detach_group);
+
 phys_addr_t iommu_iova_to_phys(struct iommu_domain *domain,
 			       unsigned long iova)
 {
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 24004d6..d4e9a7a 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -107,6 +107,10 @@ extern int iommu_attach_device(struct iommu_domain *domain,
 			       struct device *dev);
 extern void iommu_detach_device(struct iommu_domain *domain,
 				struct device *dev);
+extern int iommu_attach_group(struct iommu_domain *domain,
+			      struct iommu_group *group);
+extern void iommu_detach_group(struct iommu_domain *domain,
+			       struct iommu_group *group);
 extern int iommu_map(struct iommu_domain *domain, unsigned long iova,
 		     phys_addr_t paddr, size_t size, int prot);
 extern size_t iommu_unmap(struct iommu_domain *domain, unsigned long iova,
@@ -194,6 +198,17 @@ static inline void iommu_detach_device(struct iommu_domain *domain,
 {
 }
 
+static inline int iommu_attach_group(struct iommu_domain *domain,
+				     struct iommu_group *group)
+{
+	return -ENODEV;
+}
+
+static inline void iommu_detach_group(struct iommu_domain *domain,
+				      struct iommu_group *group)
+{
+}
+
 static inline int iommu_map(struct iommu_domain *domain, unsigned long iova,
 			    phys_addr_t paddr, int gfp_order, int prot)
 {