[Qemu-devel] [PATCH 2/7] pc-bios/s390-ccw: handle more ECKD DASD block sizes

[Jens Freimann <jfrei@linux.vnet.ibm.com>]

From: "Eugene (jno) Dvurechenski" <jno@linux.vnet.ibm.com>

Using dasdfmt(8) to format a DASD allows to choose a block size.
There are four supported values: 512, 1024, 2048, and 4096 bytes
per block. Each block size leads to selection of new count of
sectors per track. The head count remains always the same: 15.

This empiric knowledge is used to detect ECKD DASD to IPL from.

Signed-off-by: Eugene (jno) Dvurechenski <jno@linux.vnet.ibm.com>
Reviewed-by: David Hildenbrand <dahi@linux.vnet.ibm.com>
Acked-by: Christian Borntraeger <borntraeger@de.ibm.com>
Signed-off-by: Jens Freimann <jfrei@linux.vnet.ibm.com>
---
 pc-bios/s390-ccw/virtio.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/pc-bios/s390-ccw/virtio.c b/pc-bios/s390-ccw/virtio.c
index 04977e4..6ed3dc9 100644
--- a/pc-bios/s390-ccw/virtio.c
+++ b/pc-bios/s390-ccw/virtio.c
@@ -299,14 +299,35 @@ bool virtio_disk_is_scsi(void)
         && (virtio_get_block_size()  == 512);
 }
 
+/*
+ * Other supported value pairs, if any, would need to be added here.
+ * Note: head count is always 15.
+ */
+static inline u8 virtio_eckd_sectors_for_block_size(int size)
+{
+    switch (size) {
+    case 512:
+        return 49;
+    case 1024:
+        return 33;
+    case 2048:
+        return 21;
+    case 4096:
+        return 12;
+    }
+    return 0;
+}
+
 bool virtio_disk_is_eckd(void)
 {
+    const int block_size = virtio_get_block_size();
+
     if (guessed_disk_nature) {
-        return (virtio_get_block_size()  == 4096);
+        return (block_size  == 4096);
     }
     return (blk_cfg.geometry.heads == 15)
-        && (blk_cfg.geometry.sectors == 12)
-        && (virtio_get_block_size()  == 4096);
+        && (blk_cfg.geometry.sectors ==
+            virtio_eckd_sectors_for_block_size(block_size));
 }
 
 bool virtio_ipl_disk_is_valid(void)
-- 
1.8.5.5