Re: [PATCH for-5.2 5/6] pc-bios/s390-ccw: Scan through all boot devices if none has been specified

[Thomas Huth]

On 05/08/2020 11.36, Cornelia Huck wrote:
> On Tue, 28 Jul 2020 20:37:33 +0200
> Thomas Huth <thuth@redhat.com> wrote:
> 
>> If no boot device has been specified (via "bootindex=..."), the s390-ccw
>> bios scans through all devices to find a bootable device. But so far, it
>> stops at the very first block device (including virtio-scsi controllers
>> without attached devices) that it finds, no matter whether it is bootable
>> or not. That leads to some weird situatation where it is e.g. possible
>> to boot via:
>>
>>  qemu-system-s390x -hda /path/to/disk.qcow2
>>
>> but not if there is e.g. a virtio-scsi controller specified before:
>>
>>  qemu-system-s390x -device virtio-scsi -hda /path/to/disk.qcow2
>>
>> While using "bootindex=..." is clearly the preferred way of booting
>> on s390x, we still can make the life for the users at least a little
>> bit easier if we look at all available devices to find a bootable one.
>>
>> Buglink: https://bugzilla.redhat.com/show_bug.cgi?id=1846975
>> Signed-off-by: Thomas Huth <thuth@redhat.com>
>> ---
>>  pc-bios/s390-ccw/main.c | 46 +++++++++++++++++++++++++++--------------
>>  1 file changed, 31 insertions(+), 15 deletions(-)
> 
> (...)
> 
>>  int main(void)
>>  {
>>      sclp_setup();
>>      css_setup();
>>      boot_setup();
>> -    find_boot_device();
>> -    enable_subchannel(blk_schid);
>> -    ipl_boot_device();
>> +    if (have_iplb) {
>> +        find_boot_device();
>> +        enable_subchannel(blk_schid);
>> +        ipl_boot_device();
>> +    } else {
>> +        probe_boot_device();
>> +    }
> 
> The one thing that's a bit surprising with the code is that
> enable_subchannel() sticking out now. The code looking for a boot
> device does that for all subchannels it looks at... but I think
> find_boot_device() did that for specified devices already as well, so
> it seems redundant?
> 
> Anyway, that's something that can be looked at later.

Yes, I noticed that, too ... but yes, one clean-up step at a time. I've
put it on my todo-list for later.

>>  
>>      panic("Failed to load OS from hard disk\n");
>>      return 0; /* make compiler happy */
> 
> Reviewed-by: Cornelia Huck <cohuck@redhat.com>

Thanks!

 Thomas