gru: fix cache coherency issues with instruction retry

Fix two problems related to GRU instruction failures.  Cache coherency is
not maintained for CBEs except when loading or unloading contexts.  When
reading a CBE to extract error information, the CBE must first be flushed
from the cache.

The function that reads kerrnel CBEs was reading the wrong CBE.

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>
diff --git a/drivers/misc/sgi-gru/grufault.c b/drivers/misc/sgi-gru/grufault.c
index a4898076..6d06812 100644
--- a/drivers/misc/sgi-gru/grufault.c
+++ b/drivers/misc/sgi-gru/grufault.c
@@ -614,7 +614,7 @@
 	} else if (gts->ts_gru) {
 		cbrnum = thread_cbr_number(gts, ucbnum);
 		cbe = get_cbe_by_index(gts->ts_gru, cbrnum);
-		prefetchw(cbe);/* Harmless on hardware, required for emulator */
+		gru_flush_cache(cbe);	/* CBE not coherent */
 		excdet.opc = cbe->opccpy;
 		excdet.exopc = cbe->exopccpy;
 		excdet.ecause = cbe->ecause;
@@ -622,6 +622,7 @@
 		excdet.exceptdet1 = cbe->idef3upd;
 		excdet.cbrstate = cbe->cbrstate;
 		excdet.cbrexecstatus = cbe->cbrexecstatus;
+		gru_flush_cache(cbe);
 		ret = 0;
 	} else {
 		ret = -EAGAIN;