[RFC] opening the disk in raw mode for ieee1275

[diegodo]

Hi,

we are facing some issues when we install a fresh SLES 12 SP3 with LVM 
proposal installation settings on ppc64le architecture. The steps to 
reproduce it are:

1. Install SLES 12 SP3 with an LVM proposal and put / and /boot under 
btrfs on the same LV.... This will reboot just fine.  This is the 
default LVM proposal.

2. pvcreate another disk (2nd disk) and add it to the volume group.  
lvextend the LV that holds /boot and / ... btrfs filesystem resize max / 
  to resize the file system.

Now when it reboots grub will end up in a grub rescue prompt and give 
the error:

error: disk 
'lvmid/eBY8sJ-l5YB-nVGq-dhld-lbDa-hQxT-P8eXl9/zbpPOS-yUU1-pgTr-QLJC-5jeK-d3ts-gNwtzw' 
not found.


I investigated it further and found that Grub tries to open the second 
disk through OpenFirmware and it returns INVALID_IHANDLER, since OPFW 
cannot handle disks with btrfs partitions. I managed to force the grub 
to open it in “raw mode”, appending “:0” in the end of his path, 
so grub takes care of his content. With this change, it was able to open 
the disk and even listing the lv (lvm/system-root).

However, I don't know in which step grub is expected to change this disk 
path. Could someone help me with that?


Thank you,

Diego