UBUNTU: SAUCE: rfi-flush: Add no_rfi_flush and nopti comandline options

CVE-2017-5754

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

We use the x86 'nopti' option because all the documenation on earth is
going to refer to that, and we can guess what users mean when they
specify that - they want to avoid any overhead due to Meltdown
mitigations.
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
Signed-off-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>

arch/powerpc/kernel/setup_64.c

@@ -838,8 +838,29 @@ early_initcall(disable_hardlockup_detector);
 #ifdef CONFIG_PPC_BOOK3S_64
 static enum l1d_flush_type enabled_flush_types;
 static void *l1d_flush_fallback_area;
+static bool no_rfi_flush;
 bool rfi_flush;
 
+static int __init handle_no_rfi_flush(char *p)
+{
+	pr_info("rfi-flush: disabled on command line.");
+	no_rfi_flush = true;
+	return 0;
+}
+early_param("no_rfi_flush", handle_no_rfi_flush);
+
+/*
+ * The RFI flush is not KPTI, but because users will see doco that says to use
+ * nopti we hijack that option here to also disable the RFI flush.
+ */
+static int __init handle_no_pti(char *p)
+{
+	pr_info("rfi-flush: disabling due to 'nopti' on command line.\n");
+	handle_no_rfi_flush(NULL);
+	return 0;
+}
+early_param("nopti", handle_no_pti);
+
 static void do_nothing(void *unused)
 {
 	/*
@@ -905,6 +926,8 @@ void __init setup_rfi_flush(enum l1d_flush_type types, bool enable)
 		pr_info("rfi-fixups: Using mttrig type flush\n");
 
 	enabled_flush_types = types;
+
+	if (!no_rfi_flush)
 		rfi_flush_enable(enable);
 }
 #endif /* CONFIG_PPC_BOOK3S_64 */