x86/srso: Disable the mitigation on unaffected configurations

Skip the srso cmd line parsing which is not needed on Zen1/2 with SMT
disabled and with the proper microcode applied (latter should be the
case anyway) as those are not affected.

Fixes: 5a15d8348881 ("x86/srso: Tie SBPB bit setting to microcode patch detection")
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/r/20230813104517.3346-1-bp@alien8.de

diff --git a/arch/x86/kernel/cpu/bugs.c b/arch/x86/kernel/cpu/bugs.c
index d02f73c..6c04aef 100644 (file)
--- a/arch/x86/kernel/cpu/bugs.c
+++ b/arch/x86/kernel/cpu/bugs.c
@@ -2418,8 +2418,10 @@ static void __init srso_select_mitigation(void)
                 * IBPB microcode has been applied.
                 */
                if ((boot_cpu_data.x86 < 0x19) &&
-                   (!cpu_smt_possible() || (cpu_smt_control == CPU_SMT_DISABLED)))
+                   (!cpu_smt_possible() || (cpu_smt_control == CPU_SMT_DISABLED))) {
                        setup_force_cpu_cap(X86_FEATURE_SRSO_NO);
+                       return;
+               }
        }
 
        if (retbleed_mitigation == RETBLEED_MITIGATION_IBPB) {
@@ -2696,6 +2698,9 @@ static ssize_t retbleed_show_state(char *buf)
 
 static ssize_t srso_show_state(char *buf)
 {
+       if (boot_cpu_has(X86_FEATURE_SRSO_NO))
+               return sysfs_emit(buf, "Not affected\n");
+
        return sysfs_emit(buf, "%s%s\n",
                          srso_strings[srso_mitigation],
                          (cpu_has_ibpb_brtype_microcode() ? "" : ", no microcode"));