[PATCH 01/10] iommu/ioasid: Introduce system-wide capacity

[Jacob Pan]

IOASID is a limited system-wide resource that can be allocated at
runtime. This limitation can be enumerated during boot. For example, on
x86 platforms, PCI Process Address Space ID (PASID) allocation uses
IOASID service. The number of supported PASID bits are enumerated by
extended capability register as defined in the VT-d spec.

This patch adds a helper to set the system capacity, it expected to be
set during boot prior to any allocation request.

Signed-off-by: Jacob Pan <jacob.jun.pan@xxxxxxxxxxxxxxx>
---
 drivers/iommu/ioasid.c | 15 +++++++++++++++
 include/linux/ioasid.h |  5 ++++-
 2 files changed, 19 insertions(+), 1 deletion(-)

diff --git a/drivers/iommu/ioasid.c b/drivers/iommu/ioasid.c
index 0f8dd377aada..4026e52855b9 100644
--- a/drivers/iommu/ioasid.c
+++ b/drivers/iommu/ioasid.c
@@ -17,6 +17,21 @@ struct ioasid_data {
 	struct rcu_head rcu;
 };
 
+static ioasid_t ioasid_capacity;
+static ioasid_t ioasid_capacity_avail;
+
+/* System capacity can only be set once */
+void ioasid_install_capacity(ioasid_t total)
+{
+	if (ioasid_capacity) {
+		pr_warn("IOASID capacity already set at %d\n", ioasid_capacity);
+		return;
+	}
+
+	ioasid_capacity = ioasid_capacity_avail = total;
+}
+EXPORT_SYMBOL_GPL(ioasid_install_capacity);
+
 /*
  * struct ioasid_allocator_data - Internal data structure to hold information
  * about an allocator. There are two types of allocators:
diff --git a/include/linux/ioasid.h b/include/linux/ioasid.h
index 6f000d7a0ddc..9711fa0dc357 100644
--- a/include/linux/ioasid.h
+++ b/include/linux/ioasid.h
@@ -40,7 +40,7 @@ void *ioasid_find(struct ioasid_set *set, ioasid_t ioasid,
 int ioasid_register_allocator(struct ioasid_allocator_ops *allocator);
 void ioasid_unregister_allocator(struct ioasid_allocator_ops *allocator);
 int ioasid_set_data(ioasid_t ioasid, void *data);
-
+void ioasid_install_capacity(ioasid_t total);
 #else /* !CONFIG_IOASID */
 static inline ioasid_t ioasid_alloc(struct ioasid_set *set, ioasid_t min,
 				    ioasid_t max, void *private)
@@ -72,5 +72,8 @@ static inline int ioasid_set_data(ioasid_t ioasid, void *data)
 	return -ENOTSUPP;
 }
 
+static inline void ioasid_install_capacity(ioasid_t total)
+{
+}
 #endif /* CONFIG_IOASID */
 #endif /* __LINUX_IOASID_H */
-- 
2.7.4