[PATCH v8 07/11] iommu/sva: Refactoring iommu_sva_bind/unbind_device()

Lu Baolu
2022-06-07T01:54:24Z

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 | 67 +++++++++++--------
drivers/iommu/iommu-sva-lib.c | 98 ++++++++++++++++++++++++++++
drivers/iommu/iommu.c | 119 ++++++++--------------------------
3 files changed, 165 insertions(+), 119 deletions(-)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 9173c5741447..04d3da546eee 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -39,7 +39,6 @@ struct device;
struct iommu_domain;
struct iommu_domain_ops;
struct notifier_block;
-struct iommu_sva;
struct iommu_fault_event;
struct iommu_dma_cookie;

@@ -57,6 +56,14 @@ struct iommu_domain_geometry {
bool force_aperture; /* DMA only allowed in mappable range? */
};

+/**
+ * struct iommu_sva - handle to a device-mm bond
+ */
+struct iommu_sva {
+ struct device *dev;
+ refcount_t users;
+};
+
/* Domain feature flags */
#define __IOMMU_DOMAIN_PAGING (1U << 0) /* Support for iommu_map/unmap */
#define __IOMMU_DOMAIN_DMA_API (1U << 1) /* Domain for use in DMA-API
@@ -105,6 +112,7 @@ struct iommu_domain {
};
struct { /* IOMMU_DOMAIN_SVA */
struct mm_struct *mm;
+ struct iommu_sva bond;
};
};
};
@@ -638,13 +646,6 @@ struct iommu_fwspec {
/* ATS is supported */
#define IOMMU_FWSPEC_PCI_RC_ATS (1 << 0)

-/**
- * struct iommu_sva - handle to a device-mm bond
- */
-struct iommu_sva {
- struct device *dev;
-};
-
int iommu_fwspec_init(struct device *dev, struct fwnode_handle *iommu_fwnode,
const struct iommu_ops *ops);
void iommu_fwspec_free(struct device *dev);
@@ -685,11 +686,6 @@ 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);

@@ -703,6 +699,8 @@ int iommu_attach_device_pasid(struct iommu_domain *domain, struct device *dev,
ioasid_t pasid);
void iommu_detach_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 {};
@@ -1033,21 +1031,6 @@ 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;
@@ -1093,6 +1076,12 @@ static inline void iommu_detach_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 */

/**
@@ -1118,4 +1107,26 @@ void iommu_debugfs_setup(void);
static inline void iommu_debugfs_setup(void) {}
#endif

+#ifdef CONFIG_IOMMU_SVA
+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
+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.c b/drivers/iommu/iommu-sva-lib.c
index 106506143896..1e3e2b395b1e 100644
--- a/drivers/iommu/iommu-sva-lib.c
+++ b/drivers/iommu/iommu-sva-lib.c
@@ -4,6 +4,7 @@
*/
#include <linux/mutex.h>
#include <linux/sched/mm.h>
+#include <linux/iommu.h>

#include "iommu-sva-lib.h"

@@ -69,3 +70,100 @@ struct mm_struct *iommu_sva_find(ioasid_t pasid)
return ioasid_find(&iommu_sva_pasid, pasid, __mmget_not_zero);
}
EXPORT_SYMBOL_GPL(iommu_sva_find);
+
+/**
+ * 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_domain *domain;
+ ioasid_t max_pasids;
+ int ret = -EINVAL;
+
+ /* Allocate mm->pasid if necessary. */
+ max_pasids = dev->iommu->max_pasids;
+ if (!max_pasids)
+ return ERR_PTR(-EOPNOTSUPP);
+
+ ret = iommu_sva_alloc_pasid(mm, 1, max_pasids - 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) {
+ refcount_inc(&domain->bond.users);
+ goto out_success;
+ }
+
+ /* Allocate a new domain and set it on device pasid. */
+ domain = iommu_sva_domain_alloc(dev, mm);
+ if (!domain) {
+ ret = -ENOMEM;
+ goto out_unlock;
+ }
+
+ ret = iommu_attach_device_pasid(domain, dev, mm->pasid);
+ if (ret)
+ goto out_free_domain;
+ domain->bond.dev = dev;
+ refcount_set(&domain->bond.users, 1);
+
+out_success:
+ mutex_unlock(&iommu_sva_lock);
+ return &domain->bond;
+
+out_free_domain:
+ iommu_domain_free(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_domain *domain =
+ container_of(handle, struct iommu_domain, bond);
+ ioasid_t pasid = iommu_sva_get_pasid(handle);
+
+ mutex_lock(&iommu_sva_lock);
+ if (refcount_dec_and_test(&domain->bond.users)) {
+ iommu_detach_device_pasid(domain, dev, pasid);
+ iommu_domain_free(domain);
+ }
+ mutex_unlock(&iommu_sva_lock);
+}
+EXPORT_SYMBOL_GPL(iommu_sva_unbind_device);
+
+u32 iommu_sva_get_pasid(struct iommu_sva *handle)
+{
+ struct iommu_domain *domain =
+ container_of(handle, struct iommu_domain, bond);
+
+ return domain->mm->pasid;
+}
+EXPORT_SYMBOL_GPL(iommu_sva_get_pasid);
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index e92391dcce33..19e562e03284 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2795,97 +2795,6 @@ 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
*
@@ -3370,3 +3279,31 @@ void iommu_detach_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