[RFC 1/8] iommu: Introduce a replace API for device pasid

Yi Liu
2023-09-26T09:27:16Z

From: Lu Baolu <baolu.lu@linux.intel.com>

Provide a high-level API to allow replacements of one domain with
another for specific pasid of a device. This is similar to
iommu_group_replace_domain() and it is also expected to be used
only by IOMMUFD.

Signed-off-by: Lu Baolu <baolu.lu@linux.intel.com>
Signed-off-by: Yi Liu <yi.l.liu@intel.com>
---
drivers/iommu/iommu-priv.h | 2 ++
drivers/iommu/iommu.c | 73 ++++++++++++++++++++++++++++++--------
2 files changed, 60 insertions(+), 15 deletions(-)

diff --git a/drivers/iommu/iommu-priv.h b/drivers/iommu/iommu-priv.h
index 2024a2313348..5c32637f6325 100644
--- a/drivers/iommu/iommu-priv.h
+++ b/drivers/iommu/iommu-priv.h
@@ -19,6 +19,8 @@ static inline const struct iommu_ops *dev_iommu_ops(struct device *dev)

int iommu_group_replace_domain(struct iommu_group *group,
struct iommu_domain *new_domain);
+int iommu_replace_device_pasid(struct iommu_domain *domain,
+ struct device *dev, ioasid_t pasid);

int iommu_device_register_bus(struct iommu_device *iommu,
const struct iommu_ops *ops, struct bus_type *bus,
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index e53c9e659ae6..b47581c7b1c6 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -3382,6 +3382,27 @@ static void __iommu_remove_group_pasid(struct iommu_group *group,
}
}

+static int __iommu_group_attach_pasid(struct iommu_domain *domain,
+ struct iommu_group *group, ioasid_t pasid)
+{
+ void *curr;
+ int ret;
+
+ lockdep_assert_held(&group->mutex);
+
+ curr = xa_cmpxchg(&group->pasid_array, pasid, NULL, domain, GFP_KERNEL);
+ if (curr)
+ return xa_err(curr) ? : -EBUSY;
+
+ ret = __iommu_set_group_pasid(domain, group, pasid);
+ if (ret) {
+ __iommu_remove_group_pasid(group, pasid);
+ xa_erase(&group->pasid_array, pasid);
+ }
+
+ return ret;
+}
+
/*
* iommu_attach_device_pasid() - Attach a domain to pasid of device
* @domain: the iommu domain.
@@ -3394,7 +3415,6 @@ int iommu_attach_device_pasid(struct iommu_domain *domain,
struct device *dev, ioasid_t pasid)
{
struct iommu_group *group;
- void *curr;
int ret;

if (!domain->ops->set_dev_pasid)
@@ -3405,19 +3425,9 @@ int iommu_attach_device_pasid(struct iommu_domain *domain,
return -ENODEV;

mutex_lock(&group->mutex);
- curr = xa_cmpxchg(&group->pasid_array, pasid, NULL, domain, GFP_KERNEL);
- if (curr) {
- ret = xa_err(curr) ? : -EBUSY;
- goto out_unlock;
- }
-
- ret = __iommu_set_group_pasid(domain, group, pasid);
- if (ret) {
- __iommu_remove_group_pasid(group, pasid);
- xa_erase(&group->pasid_array, pasid);
- }
-out_unlock:
+ ret = __iommu_group_attach_pasid(domain, group, pasid);
mutex_unlock(&group->mutex);
+
iommu_group_put(group);

return ret;
@@ -3433,8 +3443,8 @@ EXPORT_SYMBOL_GPL(iommu_attach_device_pasid);
* The @domain must have been attached to @pasid of the @dev with
* iommu_attach_device_pasid().
*/
-void iommu_detach_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_group *group = iommu_group_get(dev);

@@ -3447,6 +3457,39 @@ void iommu_detach_device_pasid(struct iommu_domain *domain, struct device *dev,
}
EXPORT_SYMBOL_GPL(iommu_detach_device_pasid);

+/**
+ * iommu_replace_device_pasid - replace the domain that a pasid is attached to
+ * @domain: new IOMMU domain to replace with
+ * @dev: the physical device
+ * @pasid: pasid that will be attached to the new domain
+ *
+ * This API allows the pasid to switch domains. Return 0 on success, or an
+ * error. The pasid will roll back to use the old domain if failure. The
+ * caller could call iommu_detach_device_pasid() before free the old domain
+ * in order to avoid use-after-free case.
+ */
+int iommu_replace_device_pasid(struct iommu_domain *domain,
+ struct device *dev, ioasid_t pasid)
+{
+ struct iommu_group *group = dev->iommu_group;
+ int ret;
+
+ if (!domain)
+ return -EINVAL;
+
+ if (!group)
+ return -ENODEV;
+
+ mutex_lock(&group->mutex);
+ __iommu_remove_group_pasid(group, pasid);
+ xa_erase(&group->pasid_array, pasid);
+ ret = __iommu_group_attach_pasid(domain, group, pasid);
+ mutex_unlock(&group->mutex);
+
+ return ret;
+}
+EXPORT_SYMBOL_NS_GPL(iommu_replace_device_pasid, IOMMUFD_INTERNAL);
+
/*
* iommu_get_domain_for_dev_pasid() - Retrieve domain for @pasid of @dev
* @dev: the queried device
--
2.34.1