if (notify_debug(regs, &dr6))
goto out;
- if (WARN_ON_ONCE(dr6 & DR_STEP)) {
- /*
- * Historical junk that used to handle SYSENTER single-stepping.
- * This should be unreachable now. If we survive for a while
- * without anyone hitting this warning, we'll turn this into
- * an oops.
- */
- dr6 &= ~DR_STEP;
- set_thread_flag(TIF_SINGLESTEP);
+ /*
+ * The kernel doesn't use TF single-step outside of:
+ *
+ * - Kprobes, consumed through kprobe_debug_handler()
+ * - KGDB, consumed through notify_debug()
+ *
+ * So if we get here with DR_STEP set, something is wonky.
+ *
+ * A known way to trigger this is through QEMU's GDB stub,
+ * which leaks #DB into the guest and causes IST recursion.
+ */
+ if (WARN_ON_ONCE(current->thread.debugreg6 & DR_STEP))
regs->flags &= ~X86_EFLAGS_TF;
- }
-
out:
instrumentation_end();
idtentry_exit_nmi(regs, irq_state);