3 files changed, 19 insertions, 1 deletions
diff --git a/pc-bios/s390-ccw/bootmap.c b/pc-bios/s390-ccw/bootmap.c
index fa54abb4d3..f1756796df 100644
--- a/pc-bios/s390-ccw/bootmap.c
+++ b/pc-bios/s390-ccw/bootmap.c
@@ -51,6 +51,8 @@ static void jump_to_IPL_2(void)
 
 static void jump_to_IPL_code(uint64_t address)
 {
+    /* store the subsystem information _after_ the bootmap was loaded */
+    write_subsystem_identification();
     /*
      * The IPL PSW is at address 0. We also must not overwrite the
      * content of non-BIOS memory after we loaded the guest, so we
diff --git a/pc-bios/s390-ccw/main.c b/pc-bios/s390-ccw/main.c
index dbfb40e685..f9ec2157ad 100644
--- a/pc-bios/s390-ccw/main.c
+++ b/pc-bios/s390-ccw/main.c
@@ -13,6 +13,22 @@
 
 char stack[PAGE_SIZE * 8] __attribute__((__aligned__(PAGE_SIZE)));
 uint64_t boot_value;
+struct subchannel_id blk_schid = { .one = 1 };
+
+/*
+ * Priniciples of Operations (SA22-7832-09) chapter 17 requires that
+ * a subsystem-identification is at 184-187 and bytes 188-191 are zero
+ * after list-directed-IPL and ccw-IPL.
+ */
+void write_subsystem_identification(void)
+{
+    struct subchannel_id *schid = (struct subchannel_id *) 184;
+    uint32_t *zeroes = (uint32_t *) 188;
+
+    *schid = blk_schid;
+    *zeroes = 0;
+}
+
 
 void virtio_panic(const char *string)
 {
@@ -23,7 +39,6 @@ void virtio_panic(const char *string)
 
 static void virtio_setup(uint64_t dev_info)
 {
-    struct subchannel_id blk_schid = { .one = 1 };
     struct schib schib;
     int i;
     int r;
diff --git a/pc-bios/s390-ccw/s390-ccw.h b/pc-bios/s390-ccw/s390-ccw.h
index 959aed0d0b..2b773deafa 100644
--- a/pc-bios/s390-ccw/s390-ccw.h
+++ b/pc-bios/s390-ccw/s390-ccw.h
@@ -50,6 +50,7 @@ void disabled_wait(void);
 
 /* main.c */
 void virtio_panic(const char *string);
+void write_subsystem_identification(void);
 
 /* sclp-ascii.c */
 void sclp_print(const char *string);