sparc: Break up monolithic iommu table/lock into finer graularity pools and lock

Investigation of multithreaded iperf experiments on an ethernet
interface show the iommu->lock as the hottest lock identified by
lockstat, with something of the order of  21M contentions out of
27M acquisitions, and an average wait time of 26 us for the lock.
This is not efficient. A more scalable design is to follow the ppc
model, where the iommu_table has multiple pools, each stretching
over a segment of the map, and with a separate lock for each pool.
This model allows for better parallelization of the iommu map search.

This patch adds the iommu range alloc/free function infrastructure.

Signed-off-by: Sowmini Varadhan <sowmini.varadhan@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 55 insertions, 0 deletions

diff --git a/include/linux/iommu-common.h b/include/linux/iommu-common.h
new file mode 100644
index 000000000000..6be5c863f329
--- /dev/null
+++ b/include/linux/iommu-common.h
@@ -0,0 +1,55 @@
+#ifndef _LINUX_IOMMU_COMMON_H
+#define _LINUX_IOMMU_COMMON_H
+
+#include <linux/spinlock_types.h>
+#include <linux/device.h>
+#include <asm/page.h>
+
+#define IOMMU_POOL_HASHBITS     4
+#define IOMMU_NR_POOLS          (1 << IOMMU_POOL_HASHBITS)
+
+struct iommu_pool {
+	unsigned long	start;
+	unsigned long	end;
+	unsigned long	hint;
+	spinlock_t	lock;
+};
+
+struct iommu_table;
+
+struct iommu_tbl_ops {
+	unsigned long	(*cookie_to_index)(u64, void *);
+	void		(*demap)(void *, unsigned long, unsigned long);
+	void		(*reset)(struct iommu_table *);
+};
+
+struct iommu_table {
+	unsigned long		page_table_map_base;
+	unsigned long		page_table_shift;
+	unsigned long		nr_pools;
+	const struct iommu_tbl_ops  *iommu_tbl_ops;
+	unsigned long		poolsize;
+	struct iommu_pool	arena_pool[IOMMU_NR_POOLS];
+	u32			flags;
+#define	IOMMU_HAS_LARGE_POOL	0x00000001
+	struct iommu_pool	large_pool;
+	unsigned long		*map;
+};
+
+extern void iommu_tbl_pool_init(struct iommu_table *iommu,
+				unsigned long num_entries,
+				u32 page_table_shift,
+				const struct iommu_tbl_ops *iommu_tbl_ops,
+				bool large_pool, u32 npools);
+
+extern unsigned long iommu_tbl_range_alloc(struct device *dev,
+					   struct iommu_table *iommu,
+					   unsigned long npages,
+					   unsigned long *handle,
+					   unsigned int pool_hash);
+
+extern void iommu_tbl_range_free(struct iommu_table *iommu,
+				 u64 dma_addr, unsigned long npages,
+				 bool do_demap, void *demap_arg);
+
+#endif