Revert "UBUNTU: SAUCE: rfi-flush: Rework pseries logic to be more cautious"

This reverts commit c049d338.

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/platforms/pseries/setup.c

@@ -505,27 +505,21 @@ static void pSeries_setup_rfi_flush(void)
 	enum l1d_flush_type types;
 	bool enable;
 
-	/* Enable by default */
+	/* Default to fallback in case hcall is not available */
+	types = L1D_FLUSH_FALLBACK;
 	enable = true;
 
 	rc = plpar_get_cpu_characteristics(&character, &behaviour);
 	if (rc == H_SUCCESS) {
+		/* Default to no flush, unless firmware says otherwise */
 		types = L1D_FLUSH_NONE;
-
 		if (character & H_GET_CPU_CHAR_CHAR_MTTRIG2_L1_FLUSH)
 			types |= L1D_FLUSH_MTTRIG;
 		if (character & H_GET_CPU_CHAR_CHAR_ORI30_L1_FLUSH)
 			types |= L1D_FLUSH_ORI;
 
-		/* Use fallback if nothing set in hcall */
-		if (types == L1D_FLUSH_NONE)
-			types = L1D_FLUSH_FALLBACK;
-
 		if (!(behaviour & H_GET_CPU_CHAR_BEHAV_L1_FLUSH_LOW_PRIV))
 			enable = false;
-	} else {
-		/* Default to fallback if case hcall is not available */
-		types = L1D_FLUSH_FALLBACK;
 	}
 
 	setup_rfi_flush(types, enable);