drm/ttm: Fix up io_mem_reserve / io_mem_free calling

This patch attempts to fix up shortcomings with the current calling
sequences.

1) There's a fastpath where no locking occurs and only io_mem_reserved is
   called to obtain needed info for mapping. The fastpath is set per
   memory type manager.
2) If the fastpath is disabled, io_mem_reserve and io_mem_free will be exactly
   balanced and not called recursively for the same struct ttm_mem_reg.
3) Optionally the driver can choose to enable a per memory type manager LRU
   eviction mechanism that, when io_mem_reserve returns -EAGAIN will attempt
   to kill user-space mappings of memory in that manager to free up needed
   resources

Signed-off-by: Thomas Hellstrom <thellstrom@vmware.com>
Reviewed-by: Ben Skeggs <bskeggs@redhat.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>

1 files changed, 5 insertions, 1 deletions

diff --git a/include/drm/ttm/ttm_bo_api.h b/include/drm/ttm/ttm_bo_api.h
index edacd483c59..50852aad260 100644
--- a/include/drm/ttm/ttm_bo_api.h
+++ b/include/drm/ttm/ttm_bo_api.h
@@ -74,6 +74,8 @@ struct ttm_placement {
  * @is_iomem:		is this io memory ?
  * @size:		size in byte
  * @offset:		offset from the base address
+ * @io_reserved_vm:     The VM system has a refcount in @io_reserved_count
+ * @io_reserved_count:  Refcounting the numbers of callers to ttm_mem_io_reserve
  *
  * Structure indicating the bus placement of an object.
  */
@@ -83,7 +85,8 @@ struct ttm_bus_placement {
 	unsigned long	size;
 	unsigned long	offset;
 	bool		is_iomem;
-	bool		io_reserved;
+	bool		io_reserved_vm;
+	uint64_t        io_reserved_count;
 };
 
 
@@ -235,6 +238,7 @@ struct ttm_buffer_object {
 	struct list_head lru;
 	struct list_head ddestroy;
 	struct list_head swap;
+	struct list_head io_reserve_lru;
 	uint32_t val_seq;
 	bool seq_valid;