Patch "[PATCH 26/32] x86/speculation: Support 'mitigations=' cmdline option" has been added to the 4.14-stable tree

@@ -2389,15 +2389,20 @@
 			http://repo.or.cz/w/linux-2.6/mini2440.git
 
 	mitigations=
-			Control optional mitigations for CPU vulnerabilities.
-			This is a set of curated, arch-independent options, each
-			of which is an aggregation of existing arch-specific
-			options.
+			[X86] Control optional mitigations for CPU
+			vulnerabilities.  This is a set of curated,
+			arch-independent options, each of which is an
+			aggregation of existing arch-specific options.
 
 			off
 				Disable all optional CPU mitigations.  This
 				improves system performance, but it may also
 				expose users to several CPU vulnerabilities.
+				Equivalent to: nopti [X86]
+					       nospectre_v2 [X86]
+					       spectre_v2_user=off [X86]
+					       spec_store_bypass_disable=off [X86]
+					       l1tf=off [X86]
 
 			auto (default)
 				Mitigate all CPU vulnerabilities, but leave SMT

@@ -2405,12 +2410,13 @@
 				users who don't want to be surprised by SMT
 				getting disabled across kernel upgrades, or who
 				have other ways of avoiding SMT-based attacks.
-				This is the default behavior.
+				Equivalent to: (default behavior)
 
 			auto,nosmt
 				Mitigate all CPU vulnerabilities, disabling SMT
 				if needed.  This is for users who always want to
 				be fully mitigated, even if it means losing SMT.
+				Equivalent to: l1tf=flush,nosmt [X86]
 
 	mminit_loglevel=
 			[KNL] When CONFIG_DEBUG_MEMORY_INIT is set, this

@@ -494,7 +494,8 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 	char arg[20];
 	int ret, i;
 
-	if (cmdline_find_option_bool(boot_command_line, "nospectre_v2"))
+	if (cmdline_find_option_bool(boot_command_line, "nospectre_v2") ||
+	    cpu_mitigations_off())
 		return SPECTRE_V2_CMD_NONE;
 
 	ret = cmdline_find_option(boot_command_line, "spectre_v2", arg, sizeof(arg));

@@ -756,7 +757,8 @@ static enum ssb_mitigation_cmd __init ssb_parse_cmdline(void)
 	char arg[20];
 	int ret, i;
 
-	if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable")) {
+	if (cmdline_find_option_bool(boot_command_line, "nospec_store_bypass_disable") ||
+	    cpu_mitigations_off()) {
 		return SPEC_STORE_BYPASS_CMD_NONE;
 	} else {
 		ret = cmdline_find_option(boot_command_line, "spec_store_bypass_disable",

@@ -1077,6 +1079,11 @@ static void __init l1tf_select_mitigation(void)
 	if (!boot_cpu_has_bug(X86_BUG_L1TF))
 		return;
 
+	if (cpu_mitigations_off())
+		l1tf_mitigation = L1TF_MITIGATION_OFF;
+	else if (cpu_mitigations_auto_nosmt())
+		l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
+
 	override_cache_bits(&boot_cpu_data);
 
 	switch (l1tf_mitigation) {

@@ -35,6 +35,7 @@
 #include <linux/spinlock.h>
 #include <linux/mm.h>
 #include <linux/uaccess.h>
+#include <linux/cpu.h>
 
 #include <asm/cpufeature.h>
 #include <asm/hypervisor.h>

@@ -91,7 +92,8 @@ void __init pti_check_boottime_disable(void)
 			goto autosel;
 	}
 
-	if (cmdline_find_option_bool(boot_command_line, "nopti")) {
+	if (cmdline_find_option_bool(boot_command_line, "nopti") ||
+	    cpu_mitigations_off()) {
 		pti_print_if_insecure("disabled on command line.");
 		return;
 	}