x86/kaiser: Rename and simplify X86_FEATURE_KAISER handling

Concentrate it in arch/x86/mm/kaiser.c and use the upstream string "nopti".
Signed-off-by: Borislav Petkov <bp@suse.de>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

CVE-2017-5754
Signed-off-by: Colin Ian King <colin.king@canonical.com>
Signed-off-by: Kleber Sacilotto de Souza <kleber.souza@canonical.com>

Documentation/kernel-parameters.txt

@@ -2531,7 +2531,7 @@ bytes respectively. Such letter suffixes can also be entirely omitted.
 
 	nojitter	[IA-64] Disables jitter checking for ITC timers.
 
-	nokaiser	[X86-64] Disable KAISER isolation of kernel from user.
+	nopti		[X86-64] Disable KAISER isolation of kernel from user.
 
 	no-kvmclock	[X86,KVM] Disable paravirtualized KVM clock driver
 

arch/x86/kernel/cpu/common.c

@@ -180,20 +180,6 @@ static int __init x86_sep_setup(char *s)
 }
 __setup("nosep", x86_sep_setup);
 
-static int __init x86_nokaiser_setup(char *s)
-{
-	/* nokaiser doesn't accept parameters */
-	if (s)
-		return -EINVAL;
-#ifdef CONFIG_KAISER
-	kaiser_enabled = 0;
-	setup_clear_cpu_cap(X86_FEATURE_KAISER);
-	pr_info("nokaiser: KAISER feature disabled\n");
-#endif
-	return 0;
-}
-early_param("nokaiser", x86_nokaiser_setup);
-
 /* Standard macro to see if a specific flag is changeable */
 static inline int flag_is_changeable_p(u32 flag)
 {
@@ -730,10 +716,6 @@ void get_cpu_cap(struct cpuinfo_x86 *c)
 		c->x86_power = cpuid_edx(0x80000007);
 
 	init_scattered_cpuid_features(c);
-#ifdef CONFIG_KAISER
-	if (kaiser_enabled)
-		set_cpu_cap(c, X86_FEATURE_KAISER);
-#endif
 }
 
 static void identify_cpu_without_cpuid(struct cpuinfo_x86 *c)

arch/x86/mm/kaiser.c

@@ -275,8 +275,13 @@ void __init kaiser_init(void)
 {
 	int cpu;
 
-	if (!kaiser_enabled)
+	if (!kaiser_enabled) {
+		setup_clear_cpu_cap(X86_FEATURE_KAISER);
 		return;
+	}
+
+	setup_force_cpu_cap(X86_FEATURE_KAISER);
+
 	kaiser_init_all_pgds();
 
 	for_each_possible_cpu(cpu) {
@@ -419,3 +424,16 @@ void kaiser_flush_tlb_on_return_to_user(void)
 			X86_CR3_PCID_USER_FLUSH | KAISER_SHADOW_PGD_OFFSET);
 }
 EXPORT_SYMBOL(kaiser_flush_tlb_on_return_to_user);
+
+static int __init x86_nokaiser_setup(char *s)
+{
+	/* nopti doesn't accept parameters */
+	if (s)
+		return -EINVAL;
+
+	kaiser_enabled = 0;
+	pr_info("Kernel/User page tables isolation: disabled\n");
+
+	return 0;
+}
+early_param("nopti", x86_nokaiser_setup);