FAILED: patch "[PATCH] x86/speculation: Enable cross-hyperthread spectre v2 STIBP" failed to apply to 4.4-stable tree

index 40bdaea97fe7..53eb14a65610 100644
@@ -35,12 +35,10 @@ static void __init spectre_v2_select_mitigation(void);
 static void __init ssb_select_mitigation(void);
 static void __init l1tf_select_mitigation(void);
 
-/*
- * Our boot-time value of the SPEC_CTRL MSR. We read it once so that any
- * writes to SPEC_CTRL contain whatever reserved bits have been set.
- */
-u64 __ro_after_init x86_spec_ctrl_base;
+/* The base value of the SPEC_CTRL MSR that always has to be preserved. */
+u64 x86_spec_ctrl_base;
 EXPORT_SYMBOL_GPL(x86_spec_ctrl_base);
+static DEFINE_MUTEX(spec_ctrl_mutex);
 
 /*
  * The vendor and possibly platform specific bits which can be modified in

@@ -325,6 +323,46 @@ static enum spectre_v2_mitigation_cmd __init spectre_v2_parse_cmdline(void)
 	return cmd;
 }
 
+static bool stibp_needed(void)
+{
+	if (spectre_v2_enabled == SPECTRE_V2_NONE)
+		return false;
+
+	if (!boot_cpu_has(X86_FEATURE_STIBP))
+		return false;
+
+	return true;
+}
+
+static void update_stibp_msr(void *info)
+{
+	wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
+}
+
+void arch_smt_update(void)
+{
+	u64 mask;
+
+	if (!stibp_needed())
+		return;
+
+	mutex_lock(&spec_ctrl_mutex);
+	mask = x86_spec_ctrl_base;
+	if (cpu_smt_control == CPU_SMT_ENABLED)
+		mask |= SPEC_CTRL_STIBP;
+	else
+		mask &= ~SPEC_CTRL_STIBP;
+
+	if (mask != x86_spec_ctrl_base) {
+		pr_info("Spectre v2 cross-process SMT mitigation: %s STIBP\n",
+				cpu_smt_control == CPU_SMT_ENABLED ?
+				"Enabling" : "Disabling");
+		x86_spec_ctrl_base = mask;
+		on_each_cpu(update_stibp_msr, NULL, 1);
+	}
+	mutex_unlock(&spec_ctrl_mutex);
+}
+
 static void __init spectre_v2_select_mitigation(void)
 {
 	enum spectre_v2_mitigation_cmd cmd = spectre_v2_parse_cmdline();

@@ -424,6 +462,9 @@ static void __init spectre_v2_select_mitigation(void)
 		setup_force_cpu_cap(X86_FEATURE_USE_IBRS_FW);
 		pr_info("Enabling Restricted Speculation for firmware calls\n");
 	}
+
+	/* Enable STIBP if appropriate */
+	arch_smt_update();
 }
 
 #undef pr_fmt

@@ -814,6 +855,8 @@ static ssize_t l1tf_show_state(char *buf)
 static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr,
 			       char *buf, unsigned int bug)
 {
+	int ret;
+
 	if (!boot_cpu_has_bug(bug))
 		return sprintf(buf, "Not affected\n");
 

@@ -831,10 +874,12 @@ static ssize_t cpu_show_common(struct device *dev, struct device_attribute *attr
 		return sprintf(buf, "Mitigation: __user pointer sanitization\n");
 
 	case X86_BUG_SPECTRE_V2:
-		return sprintf(buf, "%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
+		ret = sprintf(buf, "%s%s%s%s%s\n", spectre_v2_strings[spectre_v2_enabled],
 			       boot_cpu_has(X86_FEATURE_USE_IBPB) ? ", IBPB" : "",
 			       boot_cpu_has(X86_FEATURE_USE_IBRS_FW) ? ", IBRS_FW" : "",
+			       (x86_spec_ctrl_base & SPEC_CTRL_STIBP) ? ", STIBP" : "",
 			       spectre_v2_module_string());
+		return ret;
 
 	case X86_BUG_SPEC_STORE_BYPASS:
 		return sprintf(buf, "%s\n", ssb_strings[ssb_mode]);

index aa7fe85ad62e..2fb49916ea56 100644
@@ -2025,6 +2025,12 @@ static void cpuhp_online_cpu_device(unsigned int cpu)
 	kobject_uevent(&dev->kobj, KOBJ_ONLINE);
 }
 
+/*
+ * Architectures that need SMT-specific errata handling during SMT hotplug
+ * should override this.
+ */
+void __weak arch_smt_update(void) { };
+
 static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
 {
 	int cpu, ret = 0;

@@ -2051,8 +2057,10 @@ static int cpuhp_smt_disable(enum cpuhp_smt_control ctrlval)
 		 */
 		cpuhp_offline_cpu_device(cpu);
 	}
-	if (!ret)
+	if (!ret) {
 		cpu_smt_control = ctrlval;
+		arch_smt_update();
+	}
 	cpu_maps_update_done();
 	return ret;
 }

@@ -2063,6 +2071,7 @@ static int cpuhp_smt_enable(void)
 
 	cpu_maps_update_begin();
 	cpu_smt_control = CPU_SMT_ENABLED;
+	arch_smt_update();
 	for_each_present_cpu(cpu) {
 		/* Skip online CPUs and CPUs on offline nodes */
 		if (cpu_online(cpu) || !node_online(cpu_to_node(cpu)))