diff --git a/src/boot.c b/src/boot.c
index 119f290..931ec3f 100644
--- a/src/boot.c
+++ b/src/boot.c
@@ -14,7 +14,7 @@
 #include "cmos.h" // inb_cmos
 #include "paravirt.h" // romfile_loadfile
 #include "pci.h" //pci_bdf_to_*
-
+#include "probes.h"
 
 /****************************************************************
  * Boot priority ordering
@@ -512,6 +512,7 @@ call_boot_entry(struct segoff_s bootsegip, u8 bootdrv)
     // Set the magic number in ax and the boot drive in dl.
     br.dl = bootdrv;
     br.ax = 0xaa55;
+    PROBE(BOOT_OS);
     call16(&br);
 }
 
@@ -643,6 +644,7 @@ do_boot(u16 seq_nr)
 void VISIBLE32FLAT
 handle_18(void)
 {
+    PROBE(INT_18);
     debug_serial_setup();
     debug_enter(NULL, DEBUG_HDL_18);
     u16 ebda_seg = get_ebda_seg();
@@ -655,6 +657,7 @@ handle_18(void)
 void VISIBLE32FLAT
 handle_19(void)
 {
+    PROBE(INT_19);
     debug_serial_setup();
     debug_enter(NULL, DEBUG_HDL_19);
     SET_EBDA(boot_sequence, 0);
diff --git a/src/post.c b/src/post.c
index b4ad1fa..59e6a37 100644
--- a/src/post.c
+++ b/src/post.c
@@ -26,6 +26,7 @@
 #include "xen.h" // xen_probe_hvm_info
 #include "ps2port.h" // ps2port_setup
 #include "virtio-blk.h" // virtio_blk_setup
+#include "probes.h"
 
 
 /****************************************************************
@@ -354,6 +355,7 @@ dopost(void)
 void VISIBLE32FLAT
 handle_post(void)
 {
+    PROBE(POST);
     debug_serial_setup();
     dprintf(1, "Start bios (version %s)\n", VERSION);
 
diff --git a/src/probes.h b/src/probes.h
new file mode 100644
index 0000000..1ec639f
--- /dev/null
+++ b/src/probes.h
@@ -0,0 +1,25 @@
+#ifndef __PROBES_H
+#define __PROBES_H
+
+/* Copy from QEMU pc.c */
+enum {
+  PROBE_SEABIOS_POST = 1001,
+  PROBE_SEABIOS_INT_18 = 1002,
+  PROBE_SEABIOS_INT_19 = 1003,
+  PROBE_SEABIOS_BOOT_OS = 1004,
+};
+
+#define PROBE_IO_PORT 0x404
+
+static inline void _probe(u32 event)
+{
+  outl(event, PROBE_IO_PORT);
+}
+
+#define PROBE(name)				\
+  do {						\
+    dprintf(9, "PROBE " #name "\n");		\
+    _probe(PROBE_SEABIOS_ ## name);			\
+  } while (0)
+
+#endif /* __PROBES_H */