x86/bugs: Add attack vector controls for L1TF

Use attack vector controls to determine if L1TF mitigation is required.

Disable SMT if cross-thread protection is desired.

Signed-off-by: David Kaplan <david.kaplan@amd.com>
Signed-off-by: Borislav Petkov (AMD) <bp@alien8.de>
Link: https://lore.kernel.org/20250707183316.1349127-17-david.kaplan@amd.com

Author: dkaplan2

arch/x86/kernel/cpu/bugs.c

@@ -2995,17 +2995,23 @@ static void override_cache_bits(struct cpuinfo_x86 *c)
 
 static void __init l1tf_select_mitigation(void)
 {
-	if (!boot_cpu_has_bug(X86_BUG_L1TF) || cpu_mitigations_off()) {
+	if (!boot_cpu_has_bug(X86_BUG_L1TF)) {
 		l1tf_mitigation = L1TF_MITIGATION_OFF;
 		return;
 	}
 
-	if (l1tf_mitigation == L1TF_MITIGATION_AUTO) {
-		if (cpu_mitigations_auto_nosmt())
-			l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
-		else
-			l1tf_mitigation = L1TF_MITIGATION_FLUSH;
+	if (l1tf_mitigation != L1TF_MITIGATION_AUTO)
+		return;
+
+	if (!should_mitigate_vuln(X86_BUG_L1TF)) {
+		l1tf_mitigation = L1TF_MITIGATION_OFF;
+		return;
 	}
+
+	if (smt_mitigations == SMT_MITIGATIONS_ON)
+		l1tf_mitigation = L1TF_MITIGATION_FLUSH_NOSMT;
+	else
+		l1tf_mitigation = L1TF_MITIGATION_FLUSH;
 }
 
 static void __init l1tf_apply_mitigation(void)