[PATCH 8/9] iommu: Add iommu page fault cookie helpers

[Lu Baolu]

Add an xarray in iommu_fault_param as place holder for per-{device, pasid}
fault cookie. They could be used in varous cases. For example, SVA needs
to handle IO page faults through work queues to batch process all faults
in a fault group. It needs a fault cookie as a temporary storage of partial
faults, together with other meta data.

The iommufd will also use the fault cookie to store the mapping of device
object ID and a pasid of a device. This allows the iommufd to quickly
retrieve the device object ID for a given {device, pasid} pair in the hot
path of IO page fault delivery.

Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 include/linux/iommu.h | 16 ++++++++++++++++
 drivers/iommu/iommu.c | 44 +++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 60 insertions(+)

diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index c86ff10b40f3..ffd6fe1317f4 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -539,10 +539,12 @@ struct iommu_fault_event {
  * struct iommu_fault_param - per-device IOMMU fault data
  * @faults: holds the pending faults which needs response
  * @lock: protect pending faults list
+ * @pasid_cookie: per-pasid fault cookie
  */
 struct iommu_fault_param {
 	struct list_head faults;
 	struct mutex lock;
+	struct xarray pasid_cookie;
 };
 
 /**
@@ -636,6 +638,8 @@ extern void iommu_set_fault_handler(struct iommu_domain *domain,
 			iommu_fault_handler_t handler, void *token);
 void iommu_domain_set_iopf_handler(struct iommu_domain *domain,
 				   iommu_iopf_handler_t handler, void *data);
+void *iommu_set_device_fault_cookie(struct device *dev, ioasid_t pasid, void *cookie);
+void *iommu_get_device_fault_cookie(struct device *dev, ioasid_t pasid);
 
 extern void iommu_get_resv_regions(struct device *dev, struct list_head *list);
 extern void iommu_put_resv_regions(struct device *dev, struct list_head *list);
@@ -965,6 +969,18 @@ static inline void iommu_domain_set_iopf_handler(struct iommu_domain *domain,
 {
 }
 
+static inline void *iommu_set_device_fault_cookie(struct device *dev,
+						  ioasid_t pasid, void *cookie)
+{
+	return ERR_PTR(-ENODEV);
+}
+
+static inline void *iommu_get_device_fault_cookie(struct device *dev,
+						  ioasid_t pasid)
+{
+	return ERR_PTR(-ENODEV);
+}
+
 static inline void iommu_get_resv_regions(struct device *dev,
 					struct list_head *list)
 {
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 3dc59af24208..d52b827982a4 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -1336,6 +1336,50 @@ int iommu_page_response(struct device *dev,
 }
 EXPORT_SYMBOL_GPL(iommu_page_response);
 
+/**
+ * iommu_set_device_fault_cookie - Set a fault cookie for per-{device, pasid}
+ * @dev: the device to set the cookie
+ * @pasid: the pasid on this device
+ * @cookie: the opaque data
+ *
+ * Return the old cookie on success, or ERR_PTR(err#) on failure.
+ */
+void *iommu_set_device_fault_cookie(struct device *dev, ioasid_t pasid,
+				    void *cookie)
+{
+	struct iommu_fault_param *fault_param;
+	void *curr;
+
+	if (!dev->iommu || !dev->iommu->fault_param)
+		return ERR_PTR(-ENODEV);
+
+	fault_param = dev->iommu->fault_param;
+	curr = xa_store(&fault_param->pasid_cookie, pasid, cookie, GFP_KERNEL);
+
+	return xa_is_err(curr) ? ERR_PTR(xa_err(curr)) : curr;
+}
+EXPORT_SYMBOL_GPL(iommu_set_device_fault_cookie);
+
+/**
+ * iommu_get_device_fault_cookie - Get the fault cookie for {device, pasid}
+ * @dev: the device to set the cookie
+ * @pasid: the pasid on this device
+ *
+ * Return the cookie on success, or ERR_PTR(err#) on failure.
+ */
+void *iommu_get_device_fault_cookie(struct device *dev, ioasid_t pasid)
+{
+	struct iommu_fault_param *fault_param;
+
+	if (!dev->iommu || !dev->iommu->fault_param)
+		return ERR_PTR(-ENODEV);
+
+	fault_param = dev->iommu->fault_param;
+
+	return xa_load(&fault_param->pasid_cookie, pasid);
+}
+EXPORT_SYMBOL_GPL(iommu_get_device_fault_cookie);
+
 /**
  * iommu_group_id - Return ID for a group
  * @group: the group to ID
-- 
2.34.1