S390: BIOS boot from given device

Use the passed device, if there is no device, use the first applicable device.
Signed-off-by: NDominik Dingel <dingel@linux.vnet.ibm.com>
Signed-off-by: NAlexander Graf <agraf@suse.de>

pc-bios/s390-ccw/main.c

@@ -12,6 +12,7 @@
 
 struct subchannel_id blk_schid;
 char stack[PAGE_SIZE * 8] __attribute__((__aligned__(PAGE_SIZE)));
+uint64_t boot_value;
 
 void virtio_panic(const char *string)
 {
@@ -20,15 +21,22 @@ void virtio_panic(const char *string)
     while (1) { }
 }
 
-static void virtio_setup(void)
+static void virtio_setup(uint64_t dev_info)
 {
     struct schib schib;
     int i;
     int r;
     bool found = false;
-
+    bool check_devno = false;
+    uint16_t dev_no = -1;
     blk_schid.one = 1;
 
+    if (dev_info != -1) {
+        check_devno = true;
+        dev_no = dev_info & 0xffff;
+        debug_print_int("device no. ", dev_no);
+    }
+
     for (i = 0; i < 0x10000; i++) {
         blk_schid.sch_no = i;
         r = stsch_err(blk_schid, &schib);
@@ -36,9 +44,11 @@ static void virtio_setup(void)
             break;
         }
         if (schib.pmcw.dnv) {
-            if (virtio_is_blk(blk_schid)) {
-                found = true;
-                break;
+            if (!check_devno || (schib.pmcw.dev == dev_no)) {
+                if (virtio_is_blk(blk_schid)) {
+                    found = true;
+                    break;
+                }
             }
         }
     }
@@ -53,7 +63,9 @@ static void virtio_setup(void)
 int main(void)
 {
     sclp_setup();
-    virtio_setup();
+    debug_print_int("boot reg[7] ", boot_value);
+    virtio_setup(boot_value);
+
     if (zipl_load() < 0)
         sclp_print("Failed to load OS from hard disk\n");
     disabled_wait();

pc-bios/s390-ccw/start.S

@@ -14,6 +14,8 @@
 _start:
 
 larl	%r15, stack + 0x8000    /* Set up stack */
+larl    %r6, boot_value
+stg     %r7, 0(%r6)     /* save the boot_value before any function calls */
 j	main                    /* And call C */
 
 /*