[SLOF] [PATCH 0/4] Block write support for SCSI and virtio-block disks

[Thomas Huth]

On 16.11.2016 09:32, Alexey Kardashevskiy wrote:
[...]
> btw what precisely did you mean by "opens the whole disk" (place in SLOF
> where I could put a printf to see what part of disk grub is opening)?

When you open a file via the disk-label package, you can choose whether
you want to have the whole disk or just a partition. For example, if
partition 1 is the PReP partition, and you've got two more partitions 2
and 3 with FAT or EXT2 file systems, you could choose to boot from a
certain partition by typing something like:

 \ Boot from PReP partition 1:
 boot disk:1

or

 \ Boot from FAT partition 2:
 boot disk:2,\vmlinux

or

 \ Boot from EXT2 partition 3:
 boot disk:3,\boot\vmlinux

The partition number will be picked up by the disk-label package and
access is then limited to that partition.

However, if you look at what GRUB2 is doing, e.g. by enabling the client
interface debug messages with

 true to debug-client-interface?

then you can see messages like:

 ci: open disk

or:

 ci: open disk:0

which means that GRUB2 tries to use the whole disk, not a specific
partition (otherwise it would say something like "disk:1").

 Thomas