[PATCH V4 09/18] iommu/ioasid: Introduce notification APIs

Jacob Pan
2021-02-28T06:33:28Z

Relations among IOASID users largely follow a publisher-subscriber
pattern. E.g. to support guest SVA on Intel Scalable I/O Virtualization
(SIOV) enabled platforms, VFIO, IOMMU, device drivers, KVM are all users
of IOASIDs. When a state change occurs, VFIO publishes the change event
that needs to be processed by other users/subscribers.

This patch introduced two types of notifications: global and per
ioasid_set. The latter is intended for users who only needs to handle
events related to the IOASID of a given set.
For more information, refer to the kernel documentation at
Documentation/ioasid.rst.

Signed-off-by: Liu Yi L <yi.l.liu@intel.com>
Signed-off-by: Wu Hao <hao.wu@intel.com>
Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
drivers/iommu/ioasid.c | 111 +++++++++++++++++++++++++++++++++++++++--
include/linux/ioasid.h | 54 ++++++++++++++++++++
2 files changed, 161 insertions(+), 4 deletions(-)

diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
index 7707bb608bdd..56577e745c4b 100644
--- a/drivers/iommu/ioasid.c
+++ b/drivers/iommu/ioasid.c
@@ -10,12 +10,33 @@
#include <linux/spinlock.h>
#include <linux/xarray.h>

+/*
+ * An IOASID can have multiple consumers where each consumer may have
+ * hardware contexts associated with the IOASID.
+ * When a status change occurs, like on IOASID deallocation, notifier chains
+ * are used to keep the consumers in sync.
+ * This is a publisher-subscriber pattern where publisher can change the
+ * state of each IOASID, e.g. alloc/free, bind IOASID to a device and mm.
+ * On the other hand, subscribers get notified for the state change and
+ * keep local states in sync.
+ */
+static ATOMIC_NOTIFIER_HEAD(ioasid_notifier);
+static DEFINE_SPINLOCK(ioasid_nb_lock);
+
/* Default to PCIe standard 20 bit PASID */
#define PCI_PASID_MAX 0x100000
static ioasid_t ioasid_capacity = PCI_PASID_MAX;
static ioasid_t ioasid_capacity_avail = PCI_PASID_MAX;
static DEFINE_XARRAY_ALLOC(ioasid_sets);

+struct ioasid_set_nb {
+ struct list_head list;
+ struct notifier_block *nb;
+ void *token;
+ struct ioasid_set *set;
+ bool active;
+};
+
enum ioasid_state {
IOASID_STATE_IDLE,
IOASID_STATE_ACTIVE,
@@ -415,6 +436,38 @@ void ioasid_detach_data(ioasid_t ioasid)
}
EXPORT_SYMBOL_GPL(ioasid_detach_data);

+/**
+ * ioasid_notify - Send notification on a given IOASID for status change.
+ *
+ * @data: The IOASID data to which the notification will send
+ * @cmd: Notification event sent by IOASID external users, can be
+ * IOASID_BIND or IOASID_UNBIND.
+ *
+ * @flags: Special instructions, e.g. notify within a set or global by
+ * IOASID_NOTIFY_FLAG_SET or IOASID_NOTIFY_FLAG_ALL flags
+ * Caller must hold ioasid_allocator_lock and reference to the IOASID
+ */
+static int ioasid_notify(struct ioasid_data *data,
+ enum ioasid_notify_val cmd, unsigned int flags)
+{
+ struct ioasid_nb_args args = { 0 };
+ int ret = 0;
+
+ if (flags & ~(IOASID_NOTIFY_FLAG_ALL | IOASID_NOTIFY_FLAG_SET))
+ return -EINVAL;
+
+ args.id = data->id;
+ args.set = data->set;
+ args.pdata = data->private;
+ args.spid = data->spid;
+ if (flags & IOASID_NOTIFY_FLAG_ALL)
+ ret = atomic_notifier_call_chain(&ioasid_notifier, cmd, &args);
+ if (flags & IOASID_NOTIFY_FLAG_SET)
+ ret = atomic_notifier_call_chain(&data->set->nh, cmd, &args);
+
+ return ret;
+}
+
static ioasid_t ioasid_find_by_spid_locked(struct ioasid_set *set, ioasid_t spid, bool get)
{
ioasid_t ioasid = INVALID_IOASID;
@@ -468,7 +521,7 @@ int ioasid_attach_spid(ioasid_t ioasid, ioasid_t spid)
goto done_unlock;
}
data->spid = spid;
-
+ ioasid_notify(data, IOASID_NOTIFY_BIND, IOASID_NOTIFY_FLAG_SET);
done_unlock:
spin_unlock(&ioasid_allocator_lock);
return ret;
@@ -486,8 +539,8 @@ void ioasid_detach_spid(ioasid_t ioasid)
pr_err("Invalid IOASID entry %d to detach\n", ioasid);
goto done_unlock;
}
+ ioasid_notify(data, IOASID_NOTIFY_UNBIND, IOASID_NOTIFY_FLAG_SET);
data->spid = INVALID_IOASID;
-
done_unlock:
spin_unlock(&ioasid_allocator_lock);
}
@@ -603,6 +656,8 @@ struct ioasid_set *ioasid_set_alloc(void *token, ioasid_t quota, int type)
set->quota = quota;
set->id = id;
atomic_set(&set->nr_ioasids, 0);
+ ATOMIC_INIT_NOTIFIER_HEAD(&set->nh);
+
/*
* Per set XA is used to store private IDs within the set, get ready
* for ioasid_set private ID and system-wide IOASID allocation
@@ -655,7 +710,9 @@ int ioasid_set_free(struct ioasid_set *set)
int ret = 0;

spin_lock(&ioasid_allocator_lock);
+ spin_lock(&ioasid_nb_lock);
ret = ioasid_set_free_locked(set);
+ spin_unlock(&ioasid_nb_lock);
spin_unlock(&ioasid_allocator_lock);
return ret;
}
@@ -728,6 +785,7 @@ ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
goto exit_free;
}
atomic_inc(&set->nr_ioasids);
+ ioasid_notify(data, IOASID_NOTIFY_ALLOC, IOASID_NOTIFY_FLAG_SET);
goto done_unlock;
exit_free:
kfree(data);
@@ -780,9 +838,11 @@ static void ioasid_free_locked(struct ioasid_set *set, ioasid_t ioasid)
* If the refcount is 1, it means there is no other users of the IOASID
* other than IOASID core itself. There is no need to notify anyone.
*/
- if (!refcount_dec_and_test(&data->refs))
+ if (!refcount_dec_and_test(&data->refs)) {
+ ioasid_notify(data, IOASID_NOTIFY_FREE,
+ IOASID_NOTIFY_FLAG_SET | IOASID_NOTIFY_FLAG_ALL);
return;
-
+ }
ioasid_do_free_locked(data);
}

@@ -833,15 +893,39 @@ void ioasid_free_all_in_set(struct ioasid_set *set)
if (!atomic_read(&set->nr_ioasids))
return;
spin_lock(&ioasid_allocator_lock);
+ spin_lock(&ioasid_nb_lock);
xa_for_each(&set->xa, index, entry) {
ioasid_free_locked(set, index);
/* Free from per set private pool */
xa_erase(&set->xa, index);
}
+ spin_unlock(&ioasid_nb_lock);
spin_unlock(&ioasid_allocator_lock);
}
EXPORT_SYMBOL_GPL(ioasid_free_all_in_set);

+/*
+ * ioasid_find_mm_set - Retrieve IOASID set with mm token
+ * Take a reference of the set if found.
+ */
+struct ioasid_set *ioasid_find_mm_set(struct mm_struct *token)
+{
+ struct ioasid_set *set;
+ unsigned long index;
+
+ spin_lock(&ioasid_allocator_lock);
+
+ xa_for_each(&ioasid_sets, index, set) {
+ if (set->type == IOASID_SET_TYPE_MM && set->token == token)
+ goto exit_unlock;
+ }
+ set = NULL;
+exit_unlock:
+ spin_unlock(&ioasid_allocator_lock);
+ return set;
+}
+EXPORT_SYMBOL_GPL(ioasid_find_mm_set);
+
/**
* ioasid_set_for_each_ioasid
* @brief
@@ -1021,6 +1105,25 @@ void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
}
EXPORT_SYMBOL_GPL(ioasid_find);

+int ioasid_register_notifier(struct ioasid_set *set, struct notifier_block *nb)
+{
+ if (set)
+ return atomic_notifier_chain_register(&set->nh, nb);
+ else
+ return atomic_notifier_chain_register(&ioasid_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(ioasid_register_notifier);
+
+void ioasid_unregister_notifier(struct ioasid_set *set,
+ struct notifier_block *nb)
+{
+ if (set)
+ atomic_notifier_chain_unregister(&set->nh, nb);
+ else
+ atomic_notifier_chain_unregister(&ioasid_notifier, nb);
+}
+EXPORT_SYMBOL_GPL(ioasid_unregister_notifier);
+
MODULE_AUTHOR("Jean-Philippe Brucker <jean-philippe.brucker@arm.com>");
MODULE_AUTHOR("Jacob Pan <jacob.jun.pan@linux.intel.com>");
MODULE_DESCRIPTION("IO Address Space ID (IOASID) allocator");
diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
index dcab02886cb5..d8b85a04214f 100644
--- a/include/linux/ioasid.h
+++ b/include/linux/ioasid.h
@@ -58,6 +58,47 @@ struct ioasid_allocator_ops {
void *pdata;
};

+/* Notification data when IOASID status changed */
+enum ioasid_notify_val {
+ IOASID_NOTIFY_ALLOC = 1,
+ IOASID_NOTIFY_FREE,
+ IOASID_NOTIFY_BIND,
+ IOASID_NOTIFY_UNBIND,
+};
+
+#define IOASID_NOTIFY_FLAG_ALL BIT(0)
+#define IOASID_NOTIFY_FLAG_SET BIT(1)
+/**
+ * enum ioasid_notifier_prios - IOASID event notification order
+ *
+ * When status of an IOASID changes, users might need to take actions to
+ * reflect the new state. For example, when an IOASID is freed due to
+ * exception, the hardware context in virtual CPU, DMA device, and IOMMU
+ * shall be cleared and drained. Order is required to prevent life cycle
+ * problems.
+ */
+enum ioasid_notifier_prios {
+ IOASID_PRIO_LAST,
+ IOASID_PRIO_DEVICE,
+ IOASID_PRIO_IOMMU,
+ IOASID_PRIO_CPU,
+};
+
+/**
+ * struct ioasid_nb_args - Argument provided by IOASID core when notifier
+ * is called.
+ * @id: The IOASID being notified
+ * @spid: The set private ID associated with the IOASID
+ * @set: The IOASID set of @id
+ * @pdata: The private data attached to the IOASID
+ */
+struct ioasid_nb_args {
+ ioasid_t id;
+ ioasid_t spid;
+ struct ioasid_set *set;
+ void *pdata;
+};
+
#if IS_ENABLED(CONFIG_IOASID)
void ioasid_install_capacity(ioasid_t total);
int ioasid_reserve_capacity(ioasid_t nr_ioasid);
@@ -84,6 +125,10 @@ void ioasid_detach_data(ioasid_t ioasid);
int ioasid_attach_spid(ioasid_t ioasid, ioasid_t spid);
void ioasid_detach_spid(ioasid_t ioasid);
ioasid_t ioasid_find_by_spid(struct ioasid_set *set, ioasid_t spid, bool get);
+int ioasid_register_notifier(struct ioasid_set *set,
+ struct notifier_block *nb);
+void ioasid_unregister_notifier(struct ioasid_set *set,
+ struct notifier_block *nb);
void ioasid_set_for_each_ioasid(struct ioasid_set *sdata,
void (*fn)(ioasid_t id, void *data),
void *data);
@@ -149,6 +194,15 @@ static inline void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
return NULL;
}

+static inline int ioasid_register_notifier(struct notifier_block *nb)
+{
+ return -ENOTSUPP;
+}
+
+static inline void ioasid_unregister_notifier(struct notifier_block *nb)
+{
+}
+
static inline int ioasid_register_allocator(struct ioasid_allocator_ops *allocator)
{
return -ENOTSUPP;
--
2.25.1