diff --git a/arch/powerpc/kernel/security.c b/arch/powerpc/kernel/security.c
index 206475e3e0b4..4856e1a5161c 100644
--- a/arch/powerpc/kernel/security.c
+++ b/arch/powerpc/kernel/security.c
@@ -364,26 +364,27 @@ ssize_t cpu_show_spec_store_bypass(struct device *dev, struct device_attribute *
 
 static int ssb_prctl_get(struct task_struct *task)
 {
-	if (stf_enabled_flush_types == STF_BARRIER_NONE)
-		/*
-		 * We don't have an explicit signal from firmware that we're
-		 * vulnerable or not, we only have certain CPU revisions that
-		 * are known to be vulnerable.
-		 *
-		 * We assume that if we're on another CPU, where the barrier is
-		 * NONE, then we are not vulnerable.
-		 */
+	/*
+	 * The STF_BARRIER feature is on by default, so if it's off that means
+	 * firmware has explicitly said the CPU is not vulnerable via either
+	 * the hypercall or device tree.
+	 */
+	if (!security_ftr_enabled(SEC_FTR_STF_BARRIER))
 		return PR_SPEC_NOT_AFFECTED;
-	else
-		/*
-		 * If we do have a barrier type then we are vulnerable. The
-		 * barrier is not a global or per-process mitigation, so the
-		 * only value we can report here is PR_SPEC_ENABLE, which
-		 * appears as "vulnerable" in /proc.
-		 */
-		return PR_SPEC_ENABLE;
 
-	return -EINVAL;
+	/*
+	 * If the system's CPU has no known barrier (see setup_stf_barrier())
+	 * then assume that the CPU is not vulnerable.
+	 */
+	if (stf_enabled_flush_types == STF_BARRIER_NONE)
+		return PR_SPEC_NOT_AFFECTED;
+
+	/*
+	 * Otherwise the CPU is vulnerable. The barrier is not a global or
+	 * per-process mitigation, so the only value that can be reported here
+	 * is PR_SPEC_ENABLE, which appears as "vulnerable" in /proc.
+	 */
+	return PR_SPEC_ENABLE;
 }
 
 int arch_prctl_spec_ctrl_get(struct task_struct *task, unsigned long which)