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Re: [Qemu-devel] [PATCH 0/5] s390x: network boot

From: Viktor Mihajlovski
Subject: Re: [Qemu-devel] [PATCH 0/5] s390x: network boot
Date: Tue, 21 Feb 2017 14:35:57 +0100
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.7.0

On 20.02.2017 17:01, Alexander Graf wrote:
> On 20/02/2017 07:43, Thomas Huth wrote:
>> On 20.02.2017 15:19, Cornelia Huck wrote:
>>> This patchset implements network boot for s390x. You need to build
>>> a s390-netboot.img to actually perform the work (not included).
>> Do you plan to include this into the upstream QEMU repository later, or
>> will this stay an external binary?
>>> Basically, we add support for virtio-net devices into the ipl code
>>> and update the ccw bios to handle this as well.
>> Just out of curiosity: What's the reason for shipping an additional
>> binary here? Couldn't it be linked into the ccw bios as well (so that
>> it's easier for the user to select a different version with the -bios
>> parameter)?
> The "other binary" (s390-netboot.img) is the equivalent of grub or
> pxelinux in an x86 network boot environment. That one usually comes from
> a different entity and different department :).
I'd rather compare the other binary to an option ROM.
At this point in time we there's no netboot ROM, but a set of
instructions on how to build a netboot binary from a kernel and a
ramdisk, the series coverletter contains a brief version of that.

> I haven't looked at the patches in detail, but do they follow the
> "normal" PXE boot flow? Do they do a DHCP request, send a proper
> Vendor-Class-Identifier for s390x, fetch the binary described by the
> "filename" property in the DHCP ack via TFTP from next-server and run
> that one then?
It's currently not described with that level of detail, but the idea is
to skip the step of loading a syslinux equivalent, and to immediately
fetch the PXELINUX config file from the TFT next server aka siaddr and
load the kernel and ramdisk specified therein.
I.e. a simulation of the PXELINUX process is done in a similar fashion
to petitboot PXE boot.
> It would be very good to stick to that flow, so that you don't confuse
> your network admins :).
> Alex


Mit freundlichen Grüßen/Kind Regards
   Viktor Mihajlovski

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