[PATCH v3 06/14] iommu/ioasid: Introduce API to adjust the quota of an ioasid_set

[Jacob Pan]

Each ioasid_set is given a quota during allocation. As system
administrators balance resources among VMs, we shall support the
adjustment of quota at runtime. The new quota cannot be less than the
outstanding IOASIDs already allocated within the set. The extra quota
will be returned to the system-wide IOASID pool if the new quota is
smaller than the existing one.

Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
---
 drivers/iommu/ioasid.c | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 include/linux/ioasid.h |  6 ++++++
 2 files changed, 53 insertions(+)

diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
index 61e25c2375ab..cf8c7d34e2de 100644
--- a/drivers/iommu/ioasid.c
+++ b/drivers/iommu/ioasid.c
@@ -654,6 +654,53 @@ void ioasid_set_put(struct ioasid_set *set)
 EXPORT_SYMBOL_GPL(ioasid_set_put);
 
 /**
+ * ioasid_adjust_set - Adjust the quota of an IOASID set
+ * @set:	IOASID set to be assigned
+ * @quota:	Quota allowed in this set
+ *
+ * Return 0 on success. If the new quota is smaller than the number of
+ * IOASIDs already allocated, -EINVAL will be returned. No change will be
+ * made to the existing quota.
+ */
+int ioasid_adjust_set(struct ioasid_set *set, int quota)
+{
+	int ret = 0;
+
+	if (quota <= 0)
+		return -EINVAL;
+
+	spin_lock(&ioasid_allocator_lock);
+	if (set->nr_ioasids > quota) {
+		pr_err("New quota %d is smaller than outstanding IOASIDs %d\n",
+			quota, set->nr_ioasids);
+		ret = -EINVAL;
+		goto done_unlock;
+	}
+
+	if ((quota > set->quota) &&
+		(quota - set->quota > ioasid_capacity_avail)) {
+		ret = -ENOSPC;
+		goto done_unlock;
+	}
+
+	/* Return the delta back to system pool */
+	ioasid_capacity_avail += set->quota - quota;
+
+	/*
+	 * May have a policy to prevent giving all available IOASIDs
+	 * to one set. But we don't enforce here, it should be in the
+	 * upper layers.
+	 */
+	set->quota = quota;
+
+done_unlock:
+	spin_unlock(&ioasid_allocator_lock);
+
+	return ret;
+}
+EXPORT_SYMBOL_GPL(ioasid_adjust_set);
+
+/**
  * ioasid_find - Find IOASID data
  * @set: the IOASID set
  * @ioasid: the IOASID to find
diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
index 1ae213b660f0..0a5e82148eb9 100644
--- a/include/linux/ioasid.h
+++ b/include/linux/ioasid.h
@@ -62,6 +62,7 @@ struct ioasid_allocator_ops {
 void ioasid_install_capacity(ioasid_t total);
 ioasid_t ioasid_get_capacity(void);
 struct ioasid_set *ioasid_set_alloc(void *token, ioasid_t quota, int type);
+int ioasid_adjust_set(struct ioasid_set *set, int quota);
 void ioasid_set_get(struct ioasid_set *set);
 void ioasid_set_put(struct ioasid_set *set);
 
@@ -99,6 +100,11 @@ static inline struct ioasid_set *ioasid_set_alloc(void *token, ioasid_t quota, i
 	return ERR_PTR(-ENOTSUPP);
 }
 
+static inline int ioasid_adjust_set(struct ioasid_set *set, int quota)
+{
+	return -ENOTSUPP;
+}
+
 static inline void ioasid_set_put(struct ioasid_set *set)
 {
 }
-- 
2.7.4