[PATCH v2 13/13] vfio/type1: track iommu backed group attach

[Liu Yi L]

With the introduction of iommu aware mdev group, user may wrap a PF/VF
as a mdev. Such mdevs will be called as wrapped PF/VF mdevs in following
statements. If it's applied on a non-singleton iommu group, there would
be multiple domain attach on an iommu_device group (equal to iommu backed
group). Reason is that mdev group attaches is finally an iommu_device
group attach in the end. And existing vfio_domain.gorup_list has no idea
about it. Thus multiple attach would happen.

What's more, under default domain policy, group attach is allowed only
when its in-use domain is equal to its default domain as the code below:

static int __iommu_attach_group(struct iommu_domain *domain, ..)
{
	..
	if (group->default_domain && group->domain != group->default_domain)
		return -EBUSY;
	...
}

So for the above scenario, only the first group attach on the
non-singleton iommu group will be successful. Subsequent group
attaches will be failed. However, this is a fairly valid usage case
if the wrapped PF/VF mdevs and other devices are assigned to a single
VM. We may want to prevent it. In other words, the subsequent group
attaches should return success before going to __iommu_attach_group().

However, if user tries to assign the wrapped PF/VF mdevs and other
devices to different VMs, the subsequent group attaches on a single
iommu_device group should be failed. This means the subsequent group
attach should finally calls into __iommu_attach_group() and be failed.

To meet the above requirements, this patch introduces vfio_group_object
structure to track the group attach of an iommu_device group (a.ka.
iommu backed group). Each vfio_domain will have a group_obj_list to
record the vfio_group_objects. The search of the group_obj_list should
use iommu_device group if a group is mdev group.

	struct vfio_group_object {
		atomic_t		count;
		struct iommu_group	*iommu_group;
		struct vfio_domain	*domain;
		struct list_head	next;
	};

Each time, a successful group attach should either have a new
vfio_group_object created or count increasing of an existing
vfio_group_object instance. Details can be found in
vfio_domain_attach_group_object().

For group detach, should have count decreasing. Please check
vfio_domain_detach_group_object().

As the vfio_domain.group_obj_list is within vfio container(vfio_iommu)
scope, if user wants to passthru a non-singleton to multiple VMs, it
will be failed as VMs will have separate vfio containers. Also, if
vIOMMU is exposed, it will also fail the attempts of assigning multiple
devices (via vfio-pci or PF/VF wrapped mdev) to a single VM. This is
aligned with current vfio passthru rules.

Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
Cc: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
Suggested-by: Alex Williamson <alex.williamson@xxxxxxxxxx>
Signed-off-by: Liu Yi L <yi.l.liu@xxxxxxxxx>
---
 drivers/vfio/vfio_iommu_type1.c | 167 ++++++++++++++++++++++++++++++++++++----
 1 file changed, 154 insertions(+), 13 deletions(-)

diff --git a/drivers/vfio/vfio_iommu_type1.c b/drivers/vfio/vfio_iommu_type1.c
index 317430d..6a67bd6 100644
--- a/drivers/vfio/vfio_iommu_type1.c
+++ b/drivers/vfio/vfio_iommu_type1.c
@@ -75,6 +75,7 @@ struct vfio_domain {
 	struct iommu_domain	*domain;
 	struct list_head	next;
 	struct list_head	group_list;
+	struct list_head	group_obj_list;
 	int			prot;		/* IOMMU_CACHE */
 	bool			fgsp;		/* Fine-grained super pages */
 };
@@ -97,6 +98,13 @@ struct vfio_group {
 	bool			mdev_group;	/* An mdev group */
 };
 
+struct vfio_group_object {
+	atomic_t		count;
+	struct iommu_group	*iommu_group;
+	struct vfio_domain	*domain;
+	struct list_head	next;
+};
+
 /*
  * Guest RAM pinning working set or DMA target
  */
@@ -1263,6 +1271,85 @@ static struct vfio_group *find_iommu_group(struct vfio_domain *domain,
 	return NULL;
 }
 
+static struct vfio_group_object *find_iommu_group_object(
+		struct vfio_domain *domain, struct iommu_group *iommu_group)
+{
+	struct vfio_group_object *g;
+
+	list_for_each_entry(g, &domain->group_obj_list, next) {
+		if (g->iommu_group == iommu_group)
+			return g;
+	}
+
+	return NULL;
+}
+
+static void vfio_init_iommu_group_object(struct vfio_group_object *group_obj,
+		struct vfio_domain *domain, struct iommu_group *iommu_group)
+{
+	if (!group_obj || !domain || !iommu_group) {
+		WARN_ON(1);
+		return;
+	}
+	atomic_set(&group_obj->count, 1);
+	group_obj->iommu_group = iommu_group;
+	group_obj->domain = domain;
+	list_add(&group_obj->next, &domain->group_obj_list);
+}
+
+static int vfio_domain_attach_group_object(
+		struct vfio_domain *domain, struct iommu_group *iommu_group)
+{
+	struct vfio_group_object *group_obj;
+
+	group_obj = find_iommu_group_object(domain, iommu_group);
+	if (group_obj) {
+		atomic_inc(&group_obj->count);
+		return 0;
+	}
+	group_obj = kzalloc(sizeof(*group_obj), GFP_KERNEL);
+	vfio_init_iommu_group_object(group_obj, domain, iommu_group);
+	return iommu_attach_group(domain->domain, iommu_group);
+}
+
+static int vfio_domain_detach_group_object(
+		struct vfio_domain *domain, struct iommu_group *iommu_group)
+{
+	struct vfio_group_object *group_obj;
+
+	group_obj = find_iommu_group_object(domain, iommu_group);
+	if (!group_obj) {
+		WARN_ON(1);
+		return -EINVAL;
+	}
+	if (atomic_dec_if_positive(&group_obj->count) == 0) {
+		list_del(&group_obj->next);
+		kfree(group_obj);
+	}
+	iommu_detach_group(domain->domain, iommu_group);
+	return 0;
+}
+
+/*
+ * Check if an iommu backed group has been attached to a domain within
+ * a specific container (vfio_iommu). If yes, return the vfio_group_object
+ * which tracks the previous domain attach for this group. Caller of this
+ * function should hold vfio_iommu->lock.
+ */
+static struct vfio_group_object *vfio_iommu_group_object_check(
+		struct vfio_iommu *iommu, struct iommu_group *iommu_group)
+{
+	struct vfio_domain *d;
+	struct vfio_group_object *group_obj;
+
+	list_for_each_entry(d, &iommu->domain_list, next) {
+		group_obj = find_iommu_group_object(d, iommu_group);
+		if (group_obj)
+			return group_obj;
+	}
+	return NULL;
+}
+
 static bool vfio_iommu_has_sw_msi(struct iommu_group *group, phys_addr_t *base)
 {
 	struct list_head group_resv_regions;
@@ -1310,21 +1397,23 @@ static struct device *vfio_mdev_get_iommu_device(struct device *dev)
 
 static int vfio_mdev_attach_domain(struct device *dev, void *data)
 {
-	struct iommu_domain *domain = data;
+	struct vfio_domain *domain = data;
 	struct device *iommu_device;
 	struct iommu_group *group;
 
 	iommu_device = vfio_mdev_get_iommu_device(dev);
 	if (iommu_device) {
 		if (iommu_dev_feature_enabled(iommu_device, IOMMU_DEV_FEAT_AUX))
-			return iommu_aux_attach_device(domain, iommu_device);
+			return iommu_aux_attach_device(domain->domain,
+							iommu_device);
 		else {
 			group = iommu_group_get(iommu_device);
 			if (!group) {
 				WARN_ON(1);
 				return -EINVAL;
 			}
-			return iommu_attach_group(domain, group);
+			return vfio_domain_attach_group_object(
+							domain, group);
 		}
 	}
 
@@ -1333,21 +1422,22 @@ static int vfio_mdev_attach_domain(struct device *dev, void *data)
 
 static int vfio_mdev_detach_domain(struct device *dev, void *data)
 {
-	struct iommu_domain *domain = data;
+	struct vfio_domain *domain = data;
 	struct device *iommu_device;
 	struct iommu_group *group;
 
 	iommu_device = vfio_mdev_get_iommu_device(dev);
 	if (iommu_device) {
 		if (iommu_dev_feature_enabled(iommu_device, IOMMU_DEV_FEAT_AUX))
-			iommu_aux_detach_device(domain, iommu_device);
+			iommu_aux_detach_device(domain->domain, iommu_device);
 		else {
 			group = iommu_group_get(iommu_device);
 			if (!group) {
 				WARN_ON(1);
 				return -EINVAL;
 			}
-			iommu_detach_group(domain, group);
+			return vfio_domain_detach_group_object(
+							domain, group);
 		}
 	}
 
@@ -1359,20 +1449,27 @@ static int vfio_iommu_attach_group(struct vfio_domain *domain,
 {
 	if (group->mdev_group)
 		return iommu_group_for_each_dev(group->iommu_group,
-						domain->domain,
+						domain,
 						vfio_mdev_attach_domain);
 	else
-		return iommu_attach_group(domain->domain, group->iommu_group);
+		return vfio_domain_attach_group_object(domain,
+							group->iommu_group);
 }
 
 static void vfio_iommu_detach_group(struct vfio_domain *domain,
 				    struct vfio_group *group)
 {
+	int ret;
+
 	if (group->mdev_group)
-		iommu_group_for_each_dev(group->iommu_group, domain->domain,
+		iommu_group_for_each_dev(group->iommu_group, domain,
 					 vfio_mdev_detach_domain);
-	else
-		iommu_detach_group(domain->domain, group->iommu_group);
+	else {
+		ret = vfio_domain_detach_group_object(
+						domain, group->iommu_group);
+		if (ret)
+			pr_warn("%s, deatch failed!! ret: %d", __func__, ret);
+	}
 }
 
 static bool vfio_bus_is_mdev(struct bus_type *bus)
@@ -1412,6 +1509,10 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 	int ret;
 	bool resv_msi, msi_remap;
 	phys_addr_t resv_msi_base;
+	struct vfio_group_object *group_obj = NULL;
+	struct device *iommu_device = NULL;
+	struct iommu_group *iommu_device_group;
+
 
 	mutex_lock(&iommu->lock);
 
@@ -1438,14 +1539,20 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 
 	group->iommu_group = iommu_group;
 
+	group_obj = vfio_iommu_group_object_check(iommu, group->iommu_group);
+	if (group_obj) {
+		atomic_inc(&group_obj->count);
+		list_add(&group->next, &group_obj->domain->group_list);
+		mutex_unlock(&iommu->lock);
+		return 0;
+	}
+
 	/* Determine bus_type in order to allocate a domain */
 	ret = iommu_group_for_each_dev(iommu_group, &bus, vfio_bus_type);
 	if (ret)
 		goto out_free;
 
 	if (vfio_bus_is_mdev(bus)) {
-		struct device *iommu_device = NULL;
-
 		group->mdev_group = true;
 
 		/* Determine the isolation type */
@@ -1469,6 +1576,39 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 		bus = iommu_device->bus;
 	}
 
+	/*
+	 * Check if iommu backed group attached to a domain within current
+	 * container. If yes, increase the count; If no, go ahead with a
+	 * new domain attach process.
+	 */
+	group_obj = NULL;
+	if (iommu_device) {
+		iommu_device_group = iommu_group_get(iommu_device);
+		if (!iommu_device_group) {
+			WARN_ON(1);
+			kfree(domain);
+			mutex_unlock(&iommu->lock);
+			return -EINVAL;
+		}
+		group_obj = vfio_iommu_group_object_check(iommu,
+							iommu_device_group);
+	} else
+		group_obj = vfio_iommu_group_object_check(iommu,
+							group->iommu_group);
+
+	if (group_obj) {
+		atomic_inc(&group_obj->count);
+		list_add(&group->next, &group_obj->domain->group_list);
+		kfree(domain);
+		mutex_unlock(&iommu->lock);
+		return 0;
+	}
+
+	/*
+	 * Now we are sure we want to initialize a new vfio_domain.
+	 * First step is to alloc an iommu_domain from iommu abstract
+	 * layer.
+	 */
 	domain->domain = iommu_domain_alloc(bus);
 	if (!domain->domain) {
 		ret = -EIO;
@@ -1484,6 +1624,7 @@ static int vfio_iommu_type1_attach_group(void *iommu_data,
 			goto out_domain;
 	}
 
+	INIT_LIST_HEAD(&domain->group_obj_list);
 	ret = vfio_iommu_attach_group(domain, group);
 	if (ret)
 		goto out_domain;
-- 
2.7.4