gru: fix prefetch and speculation bugs

Fix several bugs related to prefetch, ordering & speculation:

	- GRU cch_allocate() instruction causes cacheable memory
	  to be created. Add a barriers to prevent speculation
	  from prefetching data before it exists.
	- Add memory barriers before cache-flush instructions to ensure
	  that previously stored data is included in the line flushed to memory.

Signed-off-by: Jack Steiner <steiner@sgi.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 20 insertions, 2 deletions

diff --git a/drivers/misc/sgi-gru/gruhandles.c b/drivers/misc/sgi-gru/gruhandles.c
index 806419a6b44c..f1117a7637a2 100644
--- a/drivers/misc/sgi-gru/gruhandles.c
+++ b/drivers/misc/sgi-gru/gruhandles.c
@@ -91,9 +91,18 @@ static int wait_instruction_complete(void *h, enum mcs_op opc)
 
 int cch_allocate(struct gru_context_configuration_handle *cch)
 {
+	int ret;
+
 	cch->opc = CCHOP_ALLOCATE;
 	start_instruction(cch);
-	return wait_instruction_complete(cch, cchop_allocate);
+	ret = wait_instruction_complete(cch, cchop_allocate);
+
+	/*
+	 * Stop speculation into the GSEG being mapped by the previous ALLOCATE.
+	 * The GSEG memory does not exist until the ALLOCATE completes.
+	 */
+	sync_core();
+	return ret;
 }
 
 int cch_start(struct gru_context_configuration_handle *cch)
@@ -112,9 +121,18 @@ int cch_interrupt(struct gru_context_configuration_handle *cch)
 
 int cch_deallocate(struct gru_context_configuration_handle *cch)
 {
+	int ret;
+
 	cch->opc = CCHOP_DEALLOCATE;
 	start_instruction(cch);
-	return wait_instruction_complete(cch, cchop_deallocate);
+	ret = wait_instruction_complete(cch, cchop_deallocate);
+
+	/*
+	 * Stop speculation into the GSEG being unmapped by the previous
+	 * DEALLOCATE.
+	 */
+	sync_core();
+	return ret;
 }
 
 int cch_interrupt_sync(struct gru_context_configuration_handle