2 files changed, 35 insertions, 11 deletions

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index f405281bb202..05a252e5178d 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -4241,11 +4241,23 @@
                                   per thread.  The mitigation control state
                                   is inherited on fork.
 
+                        prctl,ibpb
+                                - Like "prctl" above, but only STIBP is
+                                  controlled per thread. IBPB is issued
+                                  always when switching between different user
+                                  space processes.
+
                         seccomp
                                 - Same as "prctl" above, but all seccomp
                                   threads will enable the mitigation unless
                                   they explicitly opt out.
 
+                        seccomp,ibpb
+                                - Like "seccomp" above, but only STIBP is
+                                  controlled per thread. IBPB is issued
+                                  always when switching between different
+                                  user space processes.
+
                         auto    - Kernel selects the mitigation depending on
                                   the available CPU features and vulnerability.
 
diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index c9e304960534..500278f5308e 100644
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -256,7 +256,9 @@ enum spectre_v2_user_cmd {
         SPECTRE_V2_USER_CMD_AUTO,
         SPECTRE_V2_USER_CMD_FORCE,
         SPECTRE_V2_USER_CMD_PRCTL,
+        SPECTRE_V2_USER_CMD_PRCTL_IBPB,
         SPECTRE_V2_USER_CMD_SECCOMP,
+        SPECTRE_V2_USER_CMD_SECCOMP_IBPB,
 };
 
 static const char * const spectre_v2_user_strings[] = {
@@ -271,11 +273,13 @@ static const struct {
         enum spectre_v2_user_cmd        cmd;
         bool                            secure;
 } v2_user_options[] __initdata = {
-        { "auto",       SPECTRE_V2_USER_CMD_AUTO,       false },
-        { "off",        SPECTRE_V2_USER_CMD_NONE,       false },
-        { "on",         SPECTRE_V2_USER_CMD_FORCE,      true  },
-        { "prctl",      SPECTRE_V2_USER_CMD_PRCTL,      false },
-        { "seccomp",    SPECTRE_V2_USER_CMD_SECCOMP,    false },
+        { "auto",               SPECTRE_V2_USER_CMD_AUTO,               false },
+        { "off",                SPECTRE_V2_USER_CMD_NONE,               false },
+        { "on",                 SPECTRE_V2_USER_CMD_FORCE,              true  },
+        { "prctl",              SPECTRE_V2_USER_CMD_PRCTL,              false },
+        { "prctl,ibpb",         SPECTRE_V2_USER_CMD_PRCTL_IBPB,         false },
+        { "seccomp",            SPECTRE_V2_USER_CMD_SECCOMP,            false },
+        { "seccomp,ibpb",       SPECTRE_V2_USER_CMD_SECCOMP_IBPB,       false },
 };
 
 static void __init spec_v2_user_print_cond(const char *reason, bool secure)
@@ -321,6 +325,7 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
 {
         enum spectre_v2_user_mitigation mode = SPECTRE_V2_USER_NONE;
         bool smt_possible = IS_ENABLED(CONFIG_SMP);
+        enum spectre_v2_user_cmd cmd;
 
         if (!boot_cpu_has(X86_FEATURE_IBPB) && !boot_cpu_has(X86_FEATURE_STIBP))
                 return;
@@ -329,17 +334,20 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
             cpu_smt_control == CPU_SMT_NOT_SUPPORTED)
                 smt_possible = false;
 
-        switch (spectre_v2_parse_user_cmdline(v2_cmd)) {
+        cmd = spectre_v2_parse_user_cmdline(v2_cmd);
+        switch (cmd) {
         case SPECTRE_V2_USER_CMD_NONE:
                 goto set_mode;
         case SPECTRE_V2_USER_CMD_FORCE:
                 mode = SPECTRE_V2_USER_STRICT;
                 break;
         case SPECTRE_V2_USER_CMD_PRCTL:
+        case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
                 mode = SPECTRE_V2_USER_PRCTL;
                 break;
         case SPECTRE_V2_USER_CMD_AUTO:
         case SPECTRE_V2_USER_CMD_SECCOMP:
+        case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
                 if (IS_ENABLED(CONFIG_SECCOMP))
                         mode = SPECTRE_V2_USER_SECCOMP;
                 else
@@ -351,12 +359,15 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
         if (boot_cpu_has(X86_FEATURE_IBPB)) {
                 setup_force_cpu_cap(X86_FEATURE_USE_IBPB);
 
-                switch (mode) {
-                case SPECTRE_V2_USER_STRICT:
+                switch (cmd) {
+                case SPECTRE_V2_USER_CMD_FORCE:
+                case SPECTRE_V2_USER_CMD_PRCTL_IBPB:
+                case SPECTRE_V2_USER_CMD_SECCOMP_IBPB:
                         static_branch_enable(&switch_mm_always_ibpb);
                         break;
-                case SPECTRE_V2_USER_PRCTL:
-                case SPECTRE_V2_USER_SECCOMP:
+                case SPECTRE_V2_USER_CMD_PRCTL:
+                case SPECTRE_V2_USER_CMD_AUTO:
+                case SPECTRE_V2_USER_CMD_SECCOMP:
                         static_branch_enable(&switch_mm_cond_ibpb);
                         break;
                 default:
@@ -364,7 +375,8 @@ spectre_v2_user_select_mitigation(enum spectre_v2_mitigation_cmd v2_cmd)
                 }
 
                 pr_info("mitigation: Enabling %s Indirect Branch Prediction Barrier\n",
-                        mode == SPECTRE_V2_USER_STRICT ? "always-on" : "conditional");
+                        static_key_enabled(&switch_mm_always_ibpb) ?
+                        "always-on" : "conditional");
         }
 
         /* If enhanced IBRS is enabled no STIPB required */