[PATCH v2 04/40] iommu/sva: Add a mm_exit callback for device drivers

[Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>]

When an mm exits, devices that were bound to it must stop performing DMA
on its PASID. Let device drivers register a callback to be notified on mm
exit. Add the callback to the sva_param structure attached to struct
device.

Signed-off-by: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>

---
v1->v2: use iommu_sva_device_init instead of a separate function
---
 drivers/iommu/iommu-sva.c | 11 ++++++++++-
 include/linux/iommu.h     |  9 +++++++--
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/drivers/iommu/iommu-sva.c b/drivers/iommu/iommu-sva.c
index 6ac679c48f3c..0700893c679d 100644
--- a/drivers/iommu/iommu-sva.c
+++ b/drivers/iommu/iommu-sva.c
@@ -303,6 +303,7 @@ static void io_mm_detach_locked(struct iommu_bond *bond)
  * @dev: the device
  * @features: bitmask of features that need to be initialized
  * @max_pasid: max PASID value supported by the device
+ * @mm_exit: callback to notify the device driver of an mm exiting
  *
  * Users of the bind()/unbind() API must call this function to initialize all
  * features required for SVA.
@@ -313,13 +314,20 @@ static void io_mm_detach_locked(struct iommu_bond *bond)
  * description. Setting @max_pasid to a non-zero value smaller than this limit
  * overrides it.
  *
+ * If the driver intends to share process address spaces, it should pass a valid
+ * @mm_exit handler. Otherwise @mm_exit can be NULL. After @mm_exit returns, the
+ * device must not issue any more transaction with the PASID given as argument.
+ * The handler gets an opaque pointer corresponding to the drvdata passed as
+ * argument of bind().
+ *
  * The device should not be performing any DMA while this function is running,
  * otherwise the behavior is undefined.
  *
  * Return 0 if initialization succeeded, or an error.
  */
 int iommu_sva_device_init(struct device *dev, unsigned long features,
-			  unsigned int max_pasid)
+			  unsigned int max_pasid,
+			  iommu_mm_exit_handler_t mm_exit)
 {
 	int ret;
 	struct iommu_sva_param *param;
@@ -337,6 +345,7 @@ int iommu_sva_device_init(struct device *dev, unsigned long features,
 
 	param->features		= features;
 	param->max_pasid	= max_pasid;
+	param->mm_exit		= mm_exit;
 	INIT_LIST_HEAD(&param->mm_list);
 
 	/*
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index d5f21719a5a0..439c8fffd836 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -61,6 +61,7 @@ struct iommu_fault_event;
 typedef int (*iommu_fault_handler_t)(struct iommu_domain *,
 			struct device *, unsigned long, int, void *);
 typedef int (*iommu_dev_fault_handler_t)(struct iommu_fault_event *, void *);
+typedef int (*iommu_mm_exit_handler_t)(struct device *dev, int pasid, void *);
 
 struct iommu_domain_geometry {
 	dma_addr_t aperture_start; /* First address that can be mapped    */
@@ -231,6 +232,7 @@ struct iommu_sva_param {
 	unsigned int min_pasid;
 	unsigned int max_pasid;
 	struct list_head mm_list;
+	iommu_mm_exit_handler_t mm_exit;
 };
 
 /**
@@ -980,17 +982,20 @@ static inline int iommu_sva_unbind_device(struct device *dev, int pasid)
 
 #ifdef CONFIG_IOMMU_SVA
 extern int iommu_sva_device_init(struct device *dev, unsigned long features,
-				 unsigned int max_pasid);
+				 unsigned int max_pasid,
+				 iommu_mm_exit_handler_t mm_exit);
 extern int iommu_sva_device_shutdown(struct device *dev);
 extern int __iommu_sva_bind_device(struct device *dev, struct mm_struct *mm,
 				   int *pasid, unsigned long flags,
 				   void *drvdata);
 extern int __iommu_sva_unbind_device(struct device *dev, int pasid);
 extern void __iommu_sva_unbind_dev_all(struct device *dev);
+
 #else /* CONFIG_IOMMU_SVA */
 static inline int iommu_sva_device_init(struct device *dev,
 					unsigned long features,
-					unsigned int max_pasid)
+					unsigned int max_pasid,
+					iommu_mm_exit_handler_t mm_exit)
 {
 	return -ENODEV;
 }
-- 
2.17.0