[RFC PATCH 1/5] iommu: Add APIs for IOMMU PASID management

[Lu Baolu]

This adds APIs for IOMMU drivers and device drivers to manage
the PASIDs used for DMA transfer and translation. It bases on
I/O ASID allocator for PASID namespace management and relies
on vendor specific IOMMU drivers for paravirtual PASIDs.

Below APIs are added:

* iommu_pasid_init(pasid)
  - Initialize a PASID consumer. The vendor specific IOMMU
    drivers are able to set the PASID range imposed by IOMMU
    hardware through a callback in iommu_ops.

* iommu_pasid_exit(pasid)
  - The PASID consumer stops consuming any PASID.

* iommu_pasid_alloc(pasid, min, max, private, *ioasid)
  - Allocate a PASID and associate a @private data with this
    PASID. The PASID value is stored in @ioaisd if returning
    success.

* iommu_pasid_free(pasid, ioasid)
  - Free a PASID to the pool so that it could be consumed by
    others.

This also adds below helpers to lookup or iterate PASID items
associated with a consumer.

* iommu_pasid_for_each(pasid, func, data)
  - Iterate PASID items of the consumer identified by @pasid,
    and call @func() against each item. An error returned from
    @func() will break the iteration.

* iommu_pasid_find(pasid, ioasid)
  - Retrieve the private data associated with @ioasid.

Cc: Ashok Raj <ashok.raj@xxxxxxxxx>
Cc: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
Cc: Kevin Tian <kevin.tian@xxxxxxxxx>
Cc: Jean-Philippe Brucker <jean-philippe.brucker@xxxxxxx>
Signed-off-by: Lu Baolu <baolu.lu@xxxxxxxxxxxxxxx>
---
 drivers/iommu/Kconfig |  1 +
 drivers/iommu/iommu.c | 89 +++++++++++++++++++++++++++++++++++++++++++
 include/linux/iommu.h | 73 +++++++++++++++++++++++++++++++++++
 3 files changed, 163 insertions(+)

diff --git a/drivers/iommu/Kconfig b/drivers/iommu/Kconfig
index d9a25715650e..39f2bb76c7b8 100644
--- a/drivers/iommu/Kconfig
+++ b/drivers/iommu/Kconfig
@@ -1,6 +1,7 @@
 # IOMMU_API always gets selected by whoever wants it.
 config IOMMU_API
 	bool
+	select IOASID
 
 menuconfig IOMMU_SUPPORT
 	bool "IOMMU Hardware Support"
diff --git a/drivers/iommu/iommu.c b/drivers/iommu/iommu.c
index 0b7c96d1425e..570b244897bb 100644
--- a/drivers/iommu/iommu.c
+++ b/drivers/iommu/iommu.c
@@ -2082,3 +2082,92 @@ void iommu_detach_device_aux(struct iommu_domain *domain, struct device *dev)
 	}
 }
 EXPORT_SYMBOL_GPL(iommu_detach_device_aux);
+
+/*
+ * APIs for PASID used by IOMMU and the device drivers which depend
+ * on IOMMU.
+ */
+struct iommu_pasid *iommu_pasid_init(struct bus_type *bus)
+{
+	struct iommu_pasid *pasid;
+	int ret;
+
+	if (!bus || !bus->iommu_ops)
+		return NULL;
+
+	pasid = kzalloc(sizeof(*pasid), GFP_KERNEL);
+	if (!pasid)
+		return NULL;
+
+	pasid->ops = bus->iommu_ops;
+	/*
+	 * The default range of an IOMMU PASID is from 0 to the full
+	 * 20bit integer.
+	 */
+	pasid->min = 0;
+	pasid->max = 0x100000;
+	/*
+	 * Give vendor specific iommu drivers a chance to set the pasid
+	 * limits imposed by the iommu hardware.
+	 */
+	if (bus->iommu_ops->pasid_init) {
+		ret = bus->iommu_ops->pasid_init(pasid);
+		if (ret) {
+			kfree(pasid);
+			return NULL;
+		}
+	}
+
+	return pasid;
+}
+EXPORT_SYMBOL_GPL(iommu_pasid_init);
+
+void iommu_pasid_exit(struct iommu_pasid *pasid)
+{
+	kfree(pasid);
+}
+EXPORT_SYMBOL_GPL(iommu_pasid_exit);
+
+int iommu_pasid_alloc(struct iommu_pasid *pasid, ioasid_t min,
+		      ioasid_t max, void *private, ioasid_t *ioasid)
+{
+	ioasid_t start, end, hw, val;
+	int ret = -EAGAIN;
+
+	start = max_t(int, min, pasid->min);
+	end = min_t(int, max, pasid->max);
+
+	if (pasid->ops->pasid_alloc)
+		ret = pasid->ops->pasid_alloc(pasid, start, end, &hw);
+
+	if (ret == -EAGAIN)
+                val = ioasid_alloc(&pasid->set, start, end, private);
+	else if (ret == 0)
+		val = ioasid_alloc(&pasid->set, hw, hw + 1, private);
+	else
+		goto hw_ret;
+
+	if (val == INVALID_IOASID)
+		goto ioasid_ret;
+
+	*ioasid = val;
+
+        return 0;
+
+ioasid_ret:
+	if (pasid->ops->pasid_free)
+		pasid->ops->pasid_free(pasid, hw);
+
+hw_ret:
+	return -ENODEV;
+}
+EXPORT_SYMBOL_GPL(iommu_pasid_alloc);
+
+void iommu_pasid_free(struct iommu_pasid *pasid, ioasid_t ioasid)
+{
+	if (pasid->ops->pasid_free)
+		pasid->ops->pasid_free(pasid, ioasid);
+
+	ioasid_free(ioasid);
+}
+EXPORT_SYMBOL_GPL(iommu_pasid_free);
diff --git a/include/linux/iommu.h b/include/linux/iommu.h
index 9bf1b3f2457a..4f5202c8170b 100644
--- a/include/linux/iommu.h
+++ b/include/linux/iommu.h
@@ -20,6 +20,7 @@
 #define __LINUX_IOMMU_H
 
 #include <linux/scatterlist.h>
+#include <linux/ioasid.h>
 #include <linux/device.h>
 #include <linux/types.h>
 #include <linux/errno.h>
@@ -48,6 +49,7 @@ struct bus_type;
 struct device;
 struct iommu_domain;
 struct notifier_block;
+struct iommu_pasid;
 
 /* iommu fault flags */
 #define IOMMU_FAULT_READ	0x0
@@ -194,6 +196,9 @@ enum iommu_dev_attr {
  * @of_xlate: add OF master IDs to iommu grouping
  * @get_dev_attr: get per device IOMMU attributions
  * @set_dev_attr: set per device IOMMU attributions
+ * @pasid_init: initialize a pasid consumer
+ * @pasid_alloc: allocate a pasid from low level driver
+ * @pasid_free: free a pasid to low level driver
  * @pgsize_bitmap: bitmap of all possible supported page sizes
  */
 struct iommu_ops {
@@ -246,6 +251,12 @@ struct iommu_ops {
 	int (*attach_dev_aux)(struct iommu_domain *domain, struct device *dev);
 	void (*detach_dev_aux)(struct iommu_domain *domain, struct device *dev);
 
+	/* IOMMU pasid callbacks */
+	int (*pasid_init)(struct iommu_pasid *pasid);
+	int (*pasid_alloc)(struct iommu_pasid *pasid, ioasid_t start,
+			   ioasid_t end, ioasid_t *ioasid);
+	void (*pasid_free)(struct iommu_pasid *pasid, ioasid_t ioasid);
+
 	unsigned long pgsize_bitmap;
 };
 
@@ -428,12 +439,41 @@ extern int iommu_attach_device_aux(struct iommu_domain *domain,
 extern void iommu_detach_device_aux(struct iommu_domain *domain,
 				    struct device *dev);
 
+/*
+ * Per IOMMU PASID consumer data.
+ */
+struct iommu_pasid {
+	ioasid_t		max;
+	ioasid_t		min;
+	struct ioasid_set	set;
+	const struct iommu_ops	*ops;
+
+	/* vendor specific iommu private data */
+	void			*priv;
+};
+
+struct iommu_pasid *iommu_pasid_init(struct bus_type *bus);
+void iommu_pasid_exit(struct iommu_pasid *pasid);
+int iommu_pasid_alloc(struct iommu_pasid *pasid, ioasid_t min,
+		      ioasid_t max, void *private, ioasid_t *ioasid);
+void iommu_pasid_free(struct iommu_pasid *pasid, ioasid_t iosid);
+static inline int
+iommu_pasid_for_each(struct iommu_pasid *pasid, ioasid_iter_t func, void *data)
+{
+	return ioasid_for_each(&pasid->set, func, data);
+}
+static inline void*
+iommu_pasid_find(struct iommu_pasid *pasid, ioasid_t ioasid)
+{
+	return ioasid_find(&pasid->set, ioasid);
+}
 #else /* CONFIG_IOMMU_API */
 
 struct iommu_ops {};
 struct iommu_group {};
 struct iommu_fwspec {};
 struct iommu_device {};
+struct iommu_pasid {};
 
 static inline bool iommu_present(struct bus_type *bus)
 {
@@ -734,6 +774,39 @@ static inline void
 iommu_detach_device_aux(struct iommu_domain *domain, struct device *dev)
 {
 }
+
+static inline struct iommu_pasid *
+iommu_pasid_init(struct bus_type *bus)
+{
+	return NULL;
+}
+
+static inline void iommu_pasid_exit(struct iommu_pasid *pasid)
+{
+}
+
+static inline int
+iommu_pasid_alloc(struct iommu_pasid *pasid, ioasid_t min,
+		  ioasid_t max, void *private, ioasid_t *ioasid)
+{
+	return -ENODEV;
+}
+
+static inline void iommu_pasid_free(struct iommu_pasid *pasid, ioasid_t iosid)
+{
+}
+
+static inline int
+iommu_pasid_for_each(struct iommu_pasid *pasid, ioasid_iter_t func, void *data)
+{
+	return -ENODEV;
+}
+
+static inline void*
+iommu_pasid_find(struct iommu_pasid *pasid, ioasid_t ioasid)
+{
+	return NULL;
+}
 #endif /* CONFIG_IOMMU_API */
 
 #ifdef CONFIG_IOMMU_DEBUGFS
-- 
2.17.1