#include <linux/device.h>
#include <linux/seq_buf.h>
+#include <asm/debugfs.h>
#include <asm/security_features.h>
#include <asm/setup.h>
do_barrier_nospec_fixups(enable);
}
+void setup_barrier_nospec(void)
+{
+ bool enable;
+
+ /*
+ * It would make sense to check SEC_FTR_SPEC_BAR_ORI31 below as well.
+ * But there's a good reason not to. The two flags we check below are
+ * both are enabled by default in the kernel, so if the hcall is not
+ * functional they will be enabled.
+ * On a system where the host firmware has been updated (so the ori
+ * functions as a barrier), but on which the hypervisor (KVM/Qemu) has
+ * not been updated, we would like to enable the barrier. Dropping the
+ * check for SEC_FTR_SPEC_BAR_ORI31 achieves that. The only downside is
+ * we potentially enable the barrier on systems where the host firmware
+ * is not updated, but that's harmless as it's a no-op.
+ */
+ enable = security_ftr_enabled(SEC_FTR_FAVOUR_SECURITY) &&
+ security_ftr_enabled(SEC_FTR_BNDS_CHK_SPEC_BAR);
+
+ enable_barrier_nospec(enable);
+}
+
+#ifdef CONFIG_DEBUG_FS
+static int barrier_nospec_set(void *data, u64 val)
+{
+ switch (val) {
+ case 0:
+ case 1:
+ break;
+ default:
+ return -EINVAL;
+ }
+
+ if (!!val == !!barrier_nospec_enabled)
+ return 0;
+
+ enable_barrier_nospec(!!val);
+
+ return 0;
+}
+
+static int barrier_nospec_get(void *data, u64 *val)
+{
+ *val = barrier_nospec_enabled ? 1 : 0;
+ return 0;
+}
+
+DEFINE_SIMPLE_ATTRIBUTE(fops_barrier_nospec,
+ barrier_nospec_get, barrier_nospec_set, "%llu\n");
+
+static __init int barrier_nospec_debugfs_init(void)
+{
+ debugfs_create_file("barrier_nospec", 0600, powerpc_debugfs_root, NULL,
+ &fops_barrier_nospec);
+ return 0;
+}
+device_initcall(barrier_nospec_debugfs_init);
+#endif /* CONFIG_DEBUG_FS */
+
ssize_t cpu_show_meltdown(struct device *dev, struct device_attribute *attr, char *buf)
{
bool thread_priv;