Re: [Qemu-devel] [RFC PATCH 00/14] Implement network booting directly into the s390-ccw BIOS

[David Hildenbrand]

On 27.06.2017 13:48, Thomas Huth wrote:
> It's already possible to do a network boot of an s390x guest with an
> external netboot image (based on a Linux installation), but it would
> be much more convenient if the s390-ccw firmware supported network
> booting right out of the box, without the need to assemble such an
> external image first.
> 
> This patch series now introduces network booting via DHCP and TFTP
> directly into the s390-ccw firmware by re-using the networking stack
> from the SLOF firmware (see https://github.com/aik/SLOF/ for details),
> and adds a driver for virtio-net-ccw devices.
> 
> Once the patches have been applied, you can download an .INS file
> via TFTP which contains the information about the further files
> that have to be loaded - kernel, initrd, etc. For example, you can
> use the built-in TFTP and DHCP server of QEMU for this by starting
> QEMU with:

Pretty cool stuff!

> 
>  qemu-system-s390x ... -device virtio-net,netdev=n1,bootindex=1 \
>        -netdev user,id=n1,tftp=/path/to/tftp,bootfile=generic.ins
> 
> The .INS file has to use the same syntax as the .INS files that can
> already be found on s390x Linux distribution installation CD-ROMs.
> 
> The patches are still in a rough shape, but before I continue here,
> I though I'd get some feedback first. Specifically:
> 
> - This adds a lot of additional code to the s390-ccw firmware (and
>   the binary is afterwards three times as big as before, 75k instead
>   of 25k) ... is that still acceptable?

As mentioned in patch #1, would it somehow be able to include code
rather than copying it and maintaining it separately?

> 
> - Is it OK to require loading an .INS file first? Or does anybody
>   have a better idea how to load multiple files (kernel, initrd,
>   etc. ...)?

Guess this is the way to go for now.

> 
> - The code from SLOF uses a different coding style (TABs instead
>   of space) ... is it OK to keep that coding style here so we
>   can share patches between SLOF and s390-ccw more easily?
> 
> - The code only supports TFTP (via UDP) ... I think that is OK for
>   most use-cases, but if we ever want to support network booting
>   via HTTP or something else that is based on TCP, we would need to
>   use something else instead... Should we maybe rather head towards
>   grub2, petitboot or something different instead?

Good question, I think all these solutions will require way more effort.

> 
>  Thomas

-- 

Thanks,

David