[PATCH V4 06/18] iommu/ioasid: Add free function and states

Jacob Pan
2021-02-28T06:38:54Z

When an actively used IOASID is freed due to exceptions, users must be
notified to perform the cleanup. The IOASID shall be put in a pending
state until all users completed their cleanup work.

This patch adds ioasid_free() function to let the caller initiate the
freeing process. Both ioasid_free() and ioasid_put() decrements
reference counts. Unlike ioasid_put(), the ioasid_free() function also
transition the IOASID to the free pending state where further
ioasid_get() is prohibited. This paves the way for FREE event
notifications that will be introduced next.

Signed-off-by: Jacob Pan <jacob.jun.pan@linux.intel.com>
---
drivers/iommu/ioasid.c | 73 ++++++++++++++++++++++++++++++++++++++++++
include/linux/ioasid.h | 5 +++
2 files changed, 78 insertions(+)

diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
index d7b476651027..a10f8154c680 100644
--- a/drivers/iommu/ioasid.c
+++ b/drivers/iommu/ioasid.c
@@ -15,8 +15,26 @@
static ioasid_t ioasid_capacity = PCI_PASID_MAX;
static ioasid_t ioasid_capacity_avail = PCI_PASID_MAX;
static DEFINE_XARRAY_ALLOC(ioasid_sets);
+
+enum ioasid_state {
+ IOASID_STATE_IDLE,
+ IOASID_STATE_ACTIVE,
+ IOASID_STATE_FREE_PENDING,
+};
+
+/**
+ * struct ioasid_data - Meta data about ioasid
+ *
+ * @id: Unique ID
+ * @refs: Number of active users
+ * @state: Track state of the IOASID
+ * @set: ioasid_set of the IOASID belongs to
+ * @private: Private data associated with the IOASID
+ * @rcu: For free after RCU grace period
+ */
struct ioasid_data {
ioasid_t id;
+ enum ioasid_state state;
struct ioasid_set *set;
void *private;
struct rcu_head rcu;
@@ -597,6 +615,7 @@ ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min, ioasid_t max,
goto exit_free;
}
data->id = id;
+ data->state = IOASID_STATE_IDLE;

/* Store IOASID in the per set data */
if (xa_err(xa_store(&set->xa, id, data, GFP_ATOMIC))) {
@@ -631,6 +650,56 @@ static void ioasid_do_free_locked(struct ioasid_data *data)
ioasid_set_free_locked(data->set);
}

+static void ioasid_free_locked(struct ioasid_set *set, ioasid_t ioasid)
+{
+ struct ioasid_data *data;
+
+ data = xa_load(&active_allocator->xa, ioasid);
+ if (!data) {
+ pr_err_ratelimited("Trying to free unknown IOASID %u\n", ioasid);
+ return;
+ }
+ if (data->set != set) {
+ pr_warn("Cannot free IOASID %u due to set ownership\n", ioasid);
+ return;
+ }
+ /* Check if the set exists */
+ if (WARN_ON(!xa_load(&ioasid_sets, data->set->id)))
+ return;
+
+ /* Free is already in progress */
+ if (data->state == IOASID_STATE_FREE_PENDING)
+ return;
+
+ data->state = IOASID_STATE_FREE_PENDING;
+ /*
+ * 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))
+ return;
+
+ ioasid_do_free_locked(data);
+}
+
+/**
+ * ioasid_free - Drop reference on an IOASID. Free if refcount drops to 0,
+ * including free from its set and system-wide list.
+ * @set: The ioasid_set to check permission with. If not NULL, IOASID
+ * free will fail if the set does not match.
+ * @ioasid: The IOASID to remove
+ *
+ * TODO: return true if all references dropped, false if async work is in
+ * progress, IOASID is in FREE_PENDING state. wait queue to be used for blocking
+ * free task.
+ */
+void ioasid_free(struct ioasid_set *set, ioasid_t ioasid)
+{
+ spin_lock(&ioasid_allocator_lock);
+ ioasid_free_locked(set, ioasid);
+ spin_unlock(&ioasid_allocator_lock);
+}
+EXPORT_SYMBOL_GPL(ioasid_free);
int ioasid_get_locked(struct ioasid_set *set, ioasid_t ioasid)
{
struct ioasid_data *data;
@@ -640,6 +709,10 @@ int ioasid_get_locked(struct ioasid_set *set, ioasid_t ioasid)
pr_err("Trying to get unknown IOASID %u\n", ioasid);
return -EINVAL;
}
+ if (data->state == IOASID_STATE_FREE_PENDING) {
+ pr_err("Trying to get IOASID being freed%u\n", ioasid);
+ return -EBUSY;
+ }

/* Check set ownership if the set is non-null */
if (set && data->set != set) {
diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
index 095f4e50dc58..cabaf0b0348f 100644
--- a/include/linux/ioasid.h
+++ b/include/linux/ioasid.h
@@ -72,6 +72,7 @@ int ioasid_get(struct ioasid_set *set, ioasid_t ioasid);
int ioasid_get_locked(struct ioasid_set *set, ioasid_t ioasid);
bool ioasid_put(struct ioasid_set *set, ioasid_t ioasid);
bool ioasid_put_locked(struct ioasid_set *set, ioasid_t ioasid);
+void ioasid_free(struct ioasid_set *set, ioasid_t ioasid);
void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
bool (*getter)(void *));
int ioasid_register_allocator(struct ioasid_allocator_ops *allocator);
@@ -105,6 +106,10 @@ static inline struct ioasid_set *ioasid_set_alloc(void *token, ioasid_t quota,
return ERR_PTR(-ENOTSUPP);
}

+static inline void ioasid_free(struct ioasid_set *set, ioasid_t ioasid)
+{
+}
+
static inline struct ioasid_set *ioasid_find_mm_set(struct mm_struct *token)
{
return NULL;
--
2.25.1