pc-bios/s390-ccw: IPL from DASD with format variations

There are two known cases of DASD format where signatures are
incomplete or absent:

1. result of <dasdfmt -d ldl -L ...> (ECKD_LDL_UNLABELED)
2. CDL with zero keys in IPL1 and IPL2 records

Now the code attempts to
1. find zIPL and use SCSI layout
2. find IPL1 and use CDL layout
3. find CMS1 and use LDL layout
3. find LNX1 and use LDL layout
4. find zIPL and use unlabeled LDL layout
5. find zIPL and use CDL layout
6. die
in this sequence.

Signed-off-by: Eugene (jno) Dvurechenski <jno@linux.vnet.ibm.com>
Acked-by: Cornelia Huck <cornelia.huck@de.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
Signed-off-by: Christian Borntraeger <borntraeger@de.ibm.com>

pc-bios/s390-ccw/bootmap.c

@@ -222,7 +222,6 @@ static void ipl_eckd_cdl(void)
 
     memset(sec, FREE_SPACE_FILLER, sizeof(sec));
     read_block(1, ipl2, "Cannot read IPL2 record at block 1");
-    IPL_assert(magic_match(ipl2, IPL2_MAGIC), "No IPL2 record");
 
     mbr = &ipl2->u.x.mbr;
     IPL_assert(magic_match(mbr, ZIPL_MAGIC), "No zIPL section in IPL2 record.");
@@ -246,12 +245,10 @@ static void ipl_eckd_cdl(void)
     /* no return */
 }
 
-static void ipl_eckd_ldl(ECKD_IPL_mode_t mode)
+static void print_eckd_ldl_msg(ECKD_IPL_mode_t mode)
 {
     LDL_VTOC *vlbl = (void *)sec; /* already read, 3rd block */
     char msg[4] = { '?', '.', '\n', '\0' };
-    block_number_t block_nr;
-    BootInfo *bip;
 
     sclp_print((mode == ECKD_CMS) ? "CMS" : "LDL");
     sclp_print(" version ");
@@ -271,12 +268,27 @@ static void ipl_eckd_ldl(ECKD_IPL_mode_t mode)
     }
     sclp_print(msg);
     print_volser(vlbl->volser);
+}
+
+static void ipl_eckd_ldl(ECKD_IPL_mode_t mode)
+{
+    block_number_t block_nr;
+    BootInfo *bip = (void *)(sec + 0x70); /* BootInfo is MBR for LDL */
+
+    if (mode != ECKD_LDL_UNLABELED) {
+        print_eckd_ldl_msg(mode);
+    }
 
     /* DO NOT read BootMap pointer (only one, xECKD) at block #2 */
 
     memset(sec, FREE_SPACE_FILLER, sizeof(sec));
-    read_block(0, sec, "Cannot read block 0");
+    read_block(0, sec, "Cannot read block 0 to grab boot info.");
-    bip = (void *)(sec + 0x70); /* "boot info" is "eckd mbr" for LDL */
+    if (mode == ECKD_LDL_UNLABELED) {
+        if (!magic_match(bip->magic, ZIPL_MAGIC)) {
+            return; /* not applicable layout */
+        }
+        sclp_print("unlabeled LDL.\n");
+    }
     verify_boot_info(bip);
 
     block_nr = eckd_block_num((void *)&(bip->bp.ipl.bm_ptr.eckd.bptr));
@@ -284,19 +296,6 @@ static void ipl_eckd_ldl(ECKD_IPL_mode_t mode)
     /* no return */
 }
 
-static void ipl_eckd(ECKD_IPL_mode_t mode)
-{
-    switch (mode) {
-    case ECKD_CDL:
-        ipl_eckd_cdl(); /* no return */
-    case ECKD_CMS:
-    case ECKD_LDL:
-        ipl_eckd_ldl(mode); /* no return */
-    default:
-        virtio_panic("\n! Unknown ECKD IPL mode !\n");
-    }
-}
-
 static void print_eckd_msg(void)
 {
     char msg[] = "Using ECKD scheme (block size *****), ";
@@ -471,7 +470,7 @@ void zipl_load(void)
     }
     print_eckd_msg();
     if (magic_match(mbr->magic, IPL1_MAGIC)) {
-        ipl_eckd(ECKD_CDL); /* no return */
+        ipl_eckd_cdl(); /* no return */
     }
 
     /* LDL/CMS? */
@@ -479,11 +478,18 @@ void zipl_load(void)
     read_block(2, vlbl, "Cannot read block 2");
 
     if (magic_match(vlbl->magic, CMS1_MAGIC)) {
-        ipl_eckd(ECKD_CMS); /* no return */
+        ipl_eckd_ldl(ECKD_CMS); /* no return */
     }
     if (magic_match(vlbl->magic, LNX1_MAGIC)) {
-        ipl_eckd(ECKD_LDL); /* no return */
+        ipl_eckd_ldl(ECKD_LDL); /* no return */
     }
 
-    virtio_panic("\n* invalid MBR magic *\n");
+    ipl_eckd_ldl(ECKD_LDL_UNLABELED); /* it still may return */
+    /*
+     * Ok, it is not a LDL by any means.
+     * It still might be a CDL with zero record keys for IPL1 and IPL2
+     */
+    ipl_eckd_cdl();
+
+    virtio_panic("\n* this can never happen *\n");
 }

pc-bios/s390-ccw/bootmap.h

@@ -257,9 +257,9 @@ typedef struct IplVolumeLabel {
 
 typedef enum {
     ECKD_NO_IPL,
-    ECKD_CDL,
     ECKD_CMS,
     ECKD_LDL,
+    ECKD_LDL_UNLABELED,
 } ECKD_IPL_mode_t;
 
 /* utility code below */