+static bool get_nx_auto_mode(void)
+{
+ /* Return true when CPU has the bug, and mitigations are ON */
+ return boot_cpu_has_bug(X86_BUG_ITLB_MULTIHIT) && !cpu_mitigations_off();
+}
+
+static void __set_nx_huge_pages(bool val)
+{
+ nx_huge_pages = itlb_multihit_kvm_mitigation = val;
+}
+
+static int set_nx_huge_pages(const char *val, const struct kernel_param *kp)
+{
+ bool old_val = nx_huge_pages;
+ bool new_val;
+
+ /* In "auto" mode deploy workaround only if CPU has the bug. */
+ if (sysfs_streq(val, "off"))
+ new_val = 0;
+ else if (sysfs_streq(val, "force"))
+ new_val = 1;
+ else if (sysfs_streq(val, "auto"))
+ new_val = get_nx_auto_mode();
+ else if (strtobool(val, &new_val) < 0)
+ return -EINVAL;
+
+ __set_nx_huge_pages(new_val);
+
+ if (new_val != old_val) {
+ struct kvm *kvm;
+ int idx;
+
+ mutex_lock(&kvm_lock);
+
+ list_for_each_entry(kvm, &vm_list, vm_list) {
+ idx = srcu_read_lock(&kvm->srcu);
+ kvm_mmu_zap_all_fast(kvm);
+ srcu_read_unlock(&kvm->srcu, idx);
+ }
+ mutex_unlock(&kvm_lock);
+ }
+
+ return 0;
+}
+