1 files changed, 25 insertions, 21 deletions

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index 29f40a92f5a8..9cab538e10f1 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -530,40 +530,44 @@ specv2_set_mode:
         arch_smt_update();
 }
 
-static bool stibp_needed(void)
+static void update_stibp_msr(void * __unused)
 {
-        /* Enhanced IBRS makes using STIBP unnecessary. */
-        if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
-                return false;
-
-        /* Check for strict user mitigation mode */
-        return spectre_v2_user == SPECTRE_V2_USER_STRICT;
+        wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
 }
 
-static void update_stibp_msr(void *info)
+/* Update x86_spec_ctrl_base in case SMT state changed. */
+static void update_stibp_strict(void)
 {
-        wrmsrl(MSR_IA32_SPEC_CTRL, x86_spec_ctrl_base);
+        u64 mask = x86_spec_ctrl_base & ~SPEC_CTRL_STIBP;
+
+        if (sched_smt_active())
+                mask |= SPEC_CTRL_STIBP;
+
+        if (mask == x86_spec_ctrl_base)
+                return;
+
+        pr_info("Update user space SMT mitigation: STIBP %s\n",
+                mask & SPEC_CTRL_STIBP ? "always-on" : "off");
+        x86_spec_ctrl_base = mask;
+        on_each_cpu(update_stibp_msr, NULL, 1);
 }
 
 void arch_smt_update(void)
 {
-        u64 mask;
-
-        if (!stibp_needed())
+        /* Enhanced IBRS implies STIBP. No update required. */
+        if (spectre_v2_enabled == SPECTRE_V2_IBRS_ENHANCED)
                 return;
 
         mutex_lock(&spec_ctrl_mutex);
 
-        mask = x86_spec_ctrl_base & ~SPEC_CTRL_STIBP;
-        if (sched_smt_active())
-                mask |= SPEC_CTRL_STIBP;
-
-        if (mask != x86_spec_ctrl_base) {
-                pr_info("Spectre v2 cross-process SMT mitigation: %s STIBP\n",
-                        mask & SPEC_CTRL_STIBP ? "Enabling" : "Disabling");
-                x86_spec_ctrl_base = mask;
-                on_each_cpu(update_stibp_msr, NULL, 1);
+        switch (spectre_v2_user) {
+        case SPECTRE_V2_USER_NONE:
+                break;
+        case SPECTRE_V2_USER_STRICT:
+                update_stibp_strict();
+                break;
         }
+
         mutex_unlock(&spec_ctrl_mutex);
 }