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, 9 insertions, 0 deletions

diff --git a/drivers/misc/sgi-gru/grumain.c b/drivers/misc/sgi-gru/grumain.c
index 944028871884..a383271d3912 100644
--- a/drivers/misc/sgi-gru/grumain.c
+++ b/drivers/misc/sgi-gru/grumain.c
@@ -499,6 +499,9 @@ static void gru_load_context_data(void *save, void *grubase, int ctxnum,
                         memset(cbe + i * GRU_HANDLE_STRIDE, 0,
                                                 GRU_CACHE_LINE_BYTES);
                 }
+                /* Flush CBE to hide race in context restart */
+                mb();
+                gru_flush_cache(cbe + i * GRU_HANDLE_STRIDE);
                 cb += GRU_HANDLE_STRIDE;
         }
 
@@ -519,6 +522,12 @@ static void gru_unload_context_data(void *save, void *grubase, int ctxnum,
         cb = gseg + GRU_CB_BASE;
         cbe = grubase + GRU_CBE_BASE;
         length = hweight64(dsrmap) * GRU_DSR_AU_BYTES;
+
+        /* CBEs may not be coherent. Flush them from cache */
+        for_each_cbr_in_allocation_map(i, &cbrmap, scr)
+                gru_flush_cache(cbe + i * GRU_HANDLE_STRIDE);
+        mb();           /* Let the CL flush complete */
+
         gru_prefetch_context(gseg, cb, cbe, cbrmap, length);
 
         for_each_cbr_in_allocation_map(i, &cbrmap, scr) {