x86/split_lock: Restructure the unwieldy switch-case in sld_state_show()

Split the handling in two parts:

1. handle the sld_state option first

2. handle X86_FEATURE flag-based printing afterwards

This splits the function nicely into two, separate logical things which
are easier to parse and understand.

Also, zap the printing in the disabled case.

Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Reviewed-by: Xiaoyao Li <xiaoyao.li@intel.com>
Link: https://patch.msgid.link/20260226145033.GAaaBduQ0rWXydOkAm@fat_crate.local

diff --git a/arch/x86/kernel/cpu/bus_lock.c b/arch/x86/kernel/cpu/bus_lock.c
index fb166662bc0d6acd9d89df8a8fe923380e9647c2..660aa9aa8bec27d287deb3494984dc5d71686f88 100644 (file)
--- a/arch/x86/kernel/cpu/bus_lock.c
+++ b/arch/x86/kernel/cpu/bus_lock.c
@@ -391,34 +391,35 @@ supported:
 
 static void sld_state_show(void)
 {
-       if (!boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT) &&
-           !boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT))
+       const char *action = "warning";
+
+       if ((!boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT) &&
+            !boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT)) ||
+           (sld_state == sld_off))
                return;
 
-       switch (sld_state) {
-       case sld_off:
-               pr_info("disabled\n");
-               break;
-       case sld_warn:
-               if (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT)) {
-                       pr_info("#AC: crashing the kernel on kernel split_locks and warning on user-space split_locks\n");
-                       if (cpuhp_setup_state(CPUHP_AP_ONLINE_DYN,
-                                             "x86/splitlock", NULL, splitlock_cpu_offline) < 0)
-                               pr_warn("No splitlock CPU offline handler\n");
-               } else if (boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT)) {
-                       pr_info("#DB: warning on user-space bus_locks\n");
-               }
-               break;
-       case sld_fatal:
-               if (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT))
-                       pr_info("#AC: crashing the kernel on kernel split_locks and sending SIGBUS on user-space split_locks\n");
-               else if (boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT))
-                       pr_info("#DB: sending SIGBUS on user-space bus_locks\n");
-               break;
-       case sld_ratelimit:
+       if (sld_state == sld_ratelimit) {
                if (boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT))
                        pr_info("#DB: setting system wide bus lock rate limit to %u/sec\n", bld_ratelimit.burst);
-               break;
+               return;
+       } else if (sld_state == sld_fatal) {
+               action = "sending SIGBUS";
+       }
+
+       if (boot_cpu_has(X86_FEATURE_SPLIT_LOCK_DETECT)) {
+               pr_info("#AC: crashing the kernel on kernel split_locks and %s on user-space split_locks\n", action);
+
+               /*
+                * This is handling the case where a CPU goes offline at the
+                * moment where split lock detection is disabled in the warn
+                * setting, see split_lock_warn(). It doesn't have any effect
+                * in the fatal case.
+                */
+               if (cpuhp_setup_state(CPUHP_AP_ONLINE_DYN, "x86/splitlock", NULL, splitlock_cpu_offline) < 0)
+                       pr_warn("No splitlock CPU offline handler\n");
+
+       } else if (boot_cpu_has(X86_FEATURE_BUS_LOCK_DETECT)) {
+               pr_info("#DB: %s on user-space bus_locks\n", action);
        }
 }