Revert "UBUNTU: SAUCE: rfi-flush: Expand the RFI section to two nop slots"

This reverts commit 00d9e152.

CVE-2017-5754

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

The functionality of this commit is 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/include/asm/exception-64s.h

@@ -58,12 +58,10 @@
  */
 #define PREPARE_RFI_TO_USER						\
 	RFI_FLUSH_FIXUP_SECTION;					\
-	nop;								\
 	nop
 
 #define PREPARE_RFI_TO_GUEST						\
 	RFI_FLUSH_FIXUP_SECTION;					\
-	nop;								\
 	nop
 
 #ifdef CONFIG_PPC_DEBUG_RFI

arch/powerpc/lib/feature-fixups.c

@@ -142,8 +142,7 @@ void do_rfi_flush_fixups(enum l1d_flush_type types)
 		dest = (void *)start + *start;
 
 		pr_devel("patching dest %lx\n", (unsigned long)dest);
-		patch_instruction(dest, 0x60000000);
-		patch_instruction(dest + 1, instr);
+		patch_instruction(dest, instr);
 	}
 
 	printk(KERN_DEBUG "rfi-fixups: patched %d locations\n", i);