[PATCH v7 06/10] iommu/sva: Refactoring iommu_sva_bind/unbind_device()

[Lu Baolu <baolu.lu@linux.intel.com>]

The existing iommu SVA interfaces are implemented by calling the SVA
specific iommu ops provided by the IOMMU drivers. There's no need for
any SVA specific ops in iommu_ops vector anymore as we can achieve
this through the generic attach/detach_dev_pasid domain ops.

This refactors the IOMMU SVA interfaces implementation by using the
set/block_pasid_dev ops and align them with the concept of the SVA
iommu domain. Put the new SVA code in the sva related file in order
to make it self-contained.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
---
 include/linux/iommu.h         |  48 ++++++++------
 drivers/iommu/iommu-sva-lib.h |   1 +
 drivers/iommu/iommu-sva-lib.c | 113 ++++++++++++++++++++++++++++++++
 drivers/iommu/iommu.c         | 119 ++++++++--------------------------
 4 files changed, 170 insertions(+), 111 deletions(-)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index e8cf82d46ce1..d9ac5ebe5bbb 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -635,6 +635,7 @@ struct iommu_fwspec {
  */
 struct iommu_sva {
 	struct device			*dev;
+	refcount_t			users;
 };
 
 int iommu_fwspec_init(struct device *dev, struct fwnode_handle *iommu_fwnode,
@@ -677,11 +678,6 @@ int iommu_dev_enable_feature(struct device *dev, enum iommu_dev_features f);
 int iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features f);
 bool iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features f);
 
-struct iommu_sva *iommu_sva_bind_device(struct device *dev,
-					struct mm_struct *mm);
-void iommu_sva_unbind_device(struct iommu_sva *handle);
-u32 iommu_sva_get_pasid(struct iommu_sva *handle);
-
 int iommu_device_use_default_domain(struct device *dev);
 void iommu_device_unuse_default_domain(struct device *dev);
 
@@ -693,6 +689,8 @@ int iommu_set_device_pasid(struct iommu_domain *domain, struct device *dev,
 			   ioasid_t pasid);
 void iommu_block_device_pasid(struct iommu_domain *domain, struct device *dev,
 			      ioasid_t pasid);
+struct iommu_domain *
+iommu_get_domain_for_dev_pasid(struct device *dev, ioasid_t pasid);
 #else /* CONFIG_IOMMU_API */
 
 struct iommu_ops {};
@@ -1023,21 +1021,6 @@ iommu_dev_disable_feature(struct device *dev, enum iommu_dev_features feat)
 	return -ENODEV;
 }
 
-static inline struct iommu_sva *
-iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
-{
-	return NULL;
-}
-
-static inline void iommu_sva_unbind_device(struct iommu_sva *handle)
-{
-}
-
-static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
-{
-	return IOMMU_PASID_INVALID;
-}
-
 static inline struct iommu_fwspec *dev_iommu_fwspec_get(struct device *dev)
 {
 	return NULL;
@@ -1077,6 +1060,12 @@ static inline void iommu_block_device_pasid(struct iommu_domain *domain,
 					    struct device *dev, ioasid_t pasid)
 {
 }
+
+static inline struct iommu_domain *
+iommu_get_domain_for_dev_pasid(struct device *dev, ioasid_t pasid)
+{
+	return NULL;
+}
 #endif /* CONFIG_IOMMU_API */
 
 /**
@@ -1108,6 +1097,10 @@ iommu_sva_alloc_domain(struct bus_type *bus, struct mm_struct *mm);
 void iommu_sva_free_domain(struct iommu_domain *domain);
 int iommu_sva_set_domain(struct iommu_domain *domain, struct device *dev,
 			 ioasid_t pasid);
+struct iommu_sva *iommu_sva_bind_device(struct device *dev,
+					struct mm_struct *mm);
+void iommu_sva_unbind_device(struct iommu_sva *handle);
+u32 iommu_sva_get_pasid(struct iommu_sva *handle);
 #else /* CONFIG_IOMMU_SVA */
 static inline struct iommu_domain *
 iommu_sva_alloc_domain(struct bus_type *bus, struct mm_struct *mm)
@@ -1124,6 +1117,21 @@ static inline int iommu_sva_set_domain(struct iommu_domain *domain,
 {
 	return -EINVAL;
 }
+
+static inline struct iommu_sva *
+iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
+{
+	return NULL;
+}
+
+static inline void iommu_sva_unbind_device(struct iommu_sva *handle)
+{
+}
+
+static inline u32 iommu_sva_get_pasid(struct iommu_sva *handle)
+{
+	return IOMMU_PASID_INVALID;
+}
 #endif /* CONFIG_IOMMU_SVA */
 
 #endif /* __LINUX_IOMMU_H */
diff --git a/drivers/iommu/iommu-sva-lib.h b/drivers/iommu/iommu-sva-lib.h
index 1be21e6b93ec..ebab5a8cb126 100644
--- a/drivers/iommu/iommu-sva-lib.h
+++ b/drivers/iommu/iommu-sva-lib.h
@@ -20,6 +20,7 @@ struct iopf_queue;
 struct iommu_sva_domain {
 	struct iommu_domain	domain;
 	struct mm_struct	*mm;
+	struct iommu_sva	bond;
 };
 
 #define to_sva_domain(d) container_of_safe(d, struct iommu_sva_domain, domain)
diff --git a/drivers/iommu/iommu-sva-lib.c b/drivers/iommu/iommu-sva-lib.c
index 210c376f6043..568e0f64edac 100644
--- a/drivers/iommu/iommu-sva-lib.c
+++ b/drivers/iommu/iommu-sva-lib.c
@@ -4,6 +4,8 @@
  */
 #include <linux/mutex.h>
 #include <linux/sched/mm.h>
+#include <linux/pci.h>
+#include <linux/pci-ats.h>
 
 #include "iommu-sva-lib.h"
 
@@ -117,3 +119,114 @@ int iommu_sva_set_domain(struct iommu_domain *domain, struct device *dev,
 
 	return iommu_set_device_pasid(domain, dev, pasid);
 }
+
+/**
+ * iommu_sva_bind_device() - Bind a process address space to a device
+ * @dev: the device
+ * @mm: the mm to bind, caller must hold a reference to mm_users
+ *
+ * Create a bond between device and address space, allowing the device to access
+ * the mm using the returned PASID. If a bond already exists between @device and
+ * @mm, it is returned and an additional reference is taken. Caller must call
+ * iommu_sva_unbind_device() to release each reference.
+ *
+ * iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) must be called first, to
+ * initialize the required SVA features.
+ *
+ * On error, returns an ERR_PTR value.
+ */
+struct iommu_sva *iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
+{
+	struct iommu_sva_domain *sva_domain;
+	struct iommu_domain *domain;
+	ioasid_t max_pasid = 0;
+	int ret = -EINVAL;
+
+	/* Allocate mm->pasid if necessary. */
+	if (!dev->iommu->iommu_dev->pasids)
+		return ERR_PTR(-EOPNOTSUPP);
+
+	if (dev_is_pci(dev)) {
+		max_pasid = pci_max_pasids(to_pci_dev(dev));
+		if (max_pasid < 0)
+			return ERR_PTR(max_pasid);
+	} else {
+		ret = device_property_read_u32(dev, "pasid-num-bits",
+					       &max_pasid);
+		if (ret)
+			return ERR_PTR(ret);
+		max_pasid = (1UL << max_pasid);
+	}
+	max_pasid = min_t(u32, max_pasid, dev->iommu->iommu_dev->pasids);
+	ret = iommu_sva_alloc_pasid(mm, 1, max_pasid - 1);
+	if (ret)
+		return ERR_PTR(ret);
+
+	mutex_lock(&iommu_sva_lock);
+	/* Search for an existing domain. */
+	domain = iommu_get_domain_for_dev_pasid(dev, mm->pasid);
+	if (domain) {
+		sva_domain = to_sva_domain(domain);
+		refcount_inc(&sva_domain->bond.users);
+		goto out_success;
+	}
+
+	/* Allocate a new domain and set it on device pasid. */
+	domain = iommu_sva_alloc_domain(dev->bus, mm);
+	if (IS_ERR(domain)) {
+		ret = PTR_ERR(domain);
+		goto out_unlock;
+	}
+
+	ret = iommu_sva_set_domain(domain, dev, mm->pasid);
+	if (ret)
+		goto out_free_domain;
+	sva_domain = to_sva_domain(domain);
+	sva_domain->bond.dev = dev;
+	refcount_set(&sva_domain->bond.users, 1);
+
+out_success:
+	mutex_unlock(&iommu_sva_lock);
+	return &sva_domain->bond;
+
+out_free_domain:
+	iommu_sva_free_domain(domain);
+out_unlock:
+	mutex_unlock(&iommu_sva_lock);
+
+	return ERR_PTR(ret);
+}
+EXPORT_SYMBOL_GPL(iommu_sva_bind_device);
+
+/**
+ * iommu_sva_unbind_device() - Remove a bond created with iommu_sva_bind_device
+ * @handle: the handle returned by iommu_sva_bind_device()
+ *
+ * Put reference to a bond between device and address space. The device should
+ * not be issuing any more transaction for this PASID. All outstanding page
+ * requests for this PASID must have been flushed to the IOMMU.
+ */
+void iommu_sva_unbind_device(struct iommu_sva *handle)
+{
+	struct device *dev = handle->dev;
+	struct iommu_sva_domain *sva_domain =
+			container_of(handle, struct iommu_sva_domain, bond);
+	ioasid_t pasid = iommu_sva_get_pasid(handle);
+
+	mutex_lock(&iommu_sva_lock);
+	if (refcount_dec_and_test(&sva_domain->bond.users)) {
+		iommu_block_device_pasid(&sva_domain->domain, dev, pasid);
+		iommu_sva_free_domain(&sva_domain->domain);
+	}
+	mutex_unlock(&iommu_sva_lock);
+}
+EXPORT_SYMBOL_GPL(iommu_sva_unbind_device);
+
+u32 iommu_sva_get_pasid(struct iommu_sva *handle)
+{
+	struct iommu_sva_domain *sva_domain =
+			container_of(handle, struct iommu_sva_domain, bond);
+
+	return sva_domain->mm->pasid;
+}
+EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 789816e4b9d6..e49c5a5b8cc1 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2766,97 +2766,6 @@ bool iommu_dev_feature_enabled(struct device *dev, enum iommu_dev_features feat)
 }
 EXPORT_SYMBOL_GPL(iommu_dev_feature_enabled);
 
-/**
- * iommu_sva_bind_device() - Bind a process address space to a device
- * @dev: the device
- * @mm: the mm to bind, caller must hold a reference to it
- *
- * Create a bond between device and address space, allowing the device to access
- * the mm using the returned PASID. If a bond already exists between @device and
- * @mm, it is returned and an additional reference is taken. Caller must call
- * iommu_sva_unbind_device() to release each reference.
- *
- * iommu_dev_enable_feature(dev, IOMMU_DEV_FEAT_SVA) must be called first, to
- * initialize the required SVA features.
- *
- * On error, returns an ERR_PTR value.
- */
-struct iommu_sva *
-iommu_sva_bind_device(struct device *dev, struct mm_struct *mm)
-{
-	struct iommu_group *group;
-	struct iommu_sva *handle = ERR_PTR(-EINVAL);
-	const struct iommu_ops *ops = dev_iommu_ops(dev);
-
-	if (!ops->sva_bind)
-		return ERR_PTR(-ENODEV);
-
-	group = iommu_group_get(dev);
-	if (!group)
-		return ERR_PTR(-ENODEV);
-
-	/* Ensure device count and domain don't change while we're binding */
-	mutex_lock(&group->mutex);
-
-	/*
-	 * To keep things simple, SVA currently doesn't support IOMMU groups
-	 * with more than one device. Existing SVA-capable systems are not
-	 * affected by the problems that required IOMMU groups (lack of ACS
-	 * isolation, device ID aliasing and other hardware issues).
-	 */
-	if (iommu_group_device_count(group) != 1)
-		goto out_unlock;
-
-	handle = ops->sva_bind(dev, mm);
-
-out_unlock:
-	mutex_unlock(&group->mutex);
-	iommu_group_put(group);
-
-	return handle;
-}
-EXPORT_SYMBOL_GPL(iommu_sva_bind_device);
-
-/**
- * iommu_sva_unbind_device() - Remove a bond created with iommu_sva_bind_device
- * @handle: the handle returned by iommu_sva_bind_device()
- *
- * Put reference to a bond between device and address space. The device should
- * not be issuing any more transaction for this PASID. All outstanding page
- * requests for this PASID must have been flushed to the IOMMU.
- */
-void iommu_sva_unbind_device(struct iommu_sva *handle)
-{
-	struct iommu_group *group;
-	struct device *dev = handle->dev;
-	const struct iommu_ops *ops = dev_iommu_ops(dev);
-
-	if (!ops->sva_unbind)
-		return;
-
-	group = iommu_group_get(dev);
-	if (!group)
-		return;
-
-	mutex_lock(&group->mutex);
-	ops->sva_unbind(handle);
-	mutex_unlock(&group->mutex);
-
-	iommu_group_put(group);
-}
-EXPORT_SYMBOL_GPL(iommu_sva_unbind_device);
-
-u32 iommu_sva_get_pasid(struct iommu_sva *handle)
-{
-	const struct iommu_ops *ops = dev_iommu_ops(handle->dev);
-
-	if (!ops->sva_get_pasid)
-		return IOMMU_PASID_INVALID;
-
-	return ops->sva_get_pasid(handle);
-}
-EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
-
 /*
  * Changes the default domain of an iommu group that has *only* one device
  *
@@ -3322,3 +3231,31 @@ void iommu_block_device_pasid(struct iommu_domain *domain, struct device *dev,
 
 	iommu_group_put(group);
 }
+
+/*
+ * This is a variant of iommu_get_domain_for_dev(). It returns the existing
+ * domain attached to pasid of a device. It's only for internal use of the
+ * IOMMU subsystem. The caller must take care to avoid any possible
+ * use-after-free case.
+ */
+struct iommu_domain *
+iommu_get_domain_for_dev_pasid(struct device *dev, ioasid_t pasid)
+{
+	struct iommu_domain *domain;
+	struct iommu_group *group;
+
+	if (!pasid_valid(pasid))
+		return NULL;
+
+	group = iommu_group_get(dev);
+	if (!group)
+		return NULL;
+	/*
+	 * The xarray protects its internal state with RCU. Hence the domain
+	 * obtained is either NULL or fully formed.
+	 */
+	domain = xa_load(&group->pasid_array, pasid);
+	iommu_group_put(group);
+
+	return domain;
+}
-- 
2.25.1