UBUNTU: SAUCE: rfi-flush: Add barriers to the fallback L1D flushing

CVE-2017-5754

BugLink: http://bugs.launchpad.net/bugs/1742772

Add a hwsync after DCBT_STOP_ALL_STREAM_IDS to order loads/
stores prior to stopping prefetch with loads and stores
as a part of the flushing. A lwsync is needed to ensure
that after we don't mix the flushing of one congruence class
with another
Signed-off-by: Balbir Singh <bsingharora@gmail.com>
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>

arch/powerpc/kernel/exceptions-64s.S

@@ -741,13 +741,15 @@ rfi_flush_fallback:
 	addi	r12,r12,8
 	mtctr	r11
 	DCBT_STOP_ALL_STREAM_IDS(r11) /* Stop prefetch streams */
-	/* XXX: Should an instruction synchronizing operation be done here? */
 
+	/* order ld/st prior to dcbt stop all streams with flushing */
+	hwsync
 1:	li	r8,0
 	.rept	8 /* 8-way set associative */
 	ldx	r11,r10,r8
 	add	r8,r8,r12
 	.endr
+	lwsync	/* Ensure that we do all 8 sets before others */
 	addi	r10,r10,128 /* 128 byte cache line */
 	bdnz	1b
 
@@ -781,13 +783,15 @@ hrfi_flush_fallback:
 	addi	r12,r12,8
 	mtctr	r11
 	DCBT_STOP_ALL_STREAM_IDS(r11) /* Stop prefetch streams */
-	/* XXX: Should an instruction synchronizing operation be done here? */
 
+	/* order ld/st prior to dcbt stop all streams with flushing */
+	hwsync
 1:	li	r8,0
 	.rept	8 /* 8-way set associative */
 	ldx	r11,r10,r8
 	add	r8,r8,r12
 	.endr
+	lwsync	/* Ensure that we do all 8 sets before others */
 	addi	r10,r10,128 /* 128 byte cache line */
 	bdnz	1b