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

This reverts commit ee71154e.

CVE-2017-5754

BugLink: http://bugs.launchpad.net/bugs/1756121

The functionality of this commit will be provided by the following
upstream patch series:
  * powerpc/64s: Allow control of RFI flush via debugfs
  * powerpc/64s: Wire up cpu_show_meltdown()
  * powerpc/powernv: Check device-tree for RFI flush settings
  * powerpc/pseries: Query hypervisor for RFI flush settings
  * powerpc/64s: Support disabling RFI flush with no_rfi_flush and nopti
  * powerpc/64s: Add support for RFI flush of L1-D cache
  * powerpc/64s: Convert slb_miss_common to use RFI_TO_USER/KERNEL
  * powerpc/64: Convert the syscall exit path to use RFI_TO_USER/KERNEL
  * powerpc/64: Convert fast_exception_return to use RFI_TO_USER/KERNEL
  * powerpc/64s: Simple RFI macro conversions
  * powerpc/64: Add macros for annotating the destination of rfid/hrfid
  * powerpc/pseries: Add H_GET_CPU_CHARACTERISTICS flags & wrapper
Signed-off-by: Juerg Haefliger <juergh@canonical.com>
Signed-off-by: Stefan Bader <stefan.bader@canonical.com>

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

@@ -741,15 +741,13 @@ 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 */
-	sync
 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
 
@@ -783,15 +781,13 @@ 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 */
-	sync
 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