[PATCH] kexec-tools: do not copy 1st kernel root= param in fs2dt.c

[Simon Horman]

Hi Dave,

On Fri, Oct 09, 2015 at 01:57:22PM +0800, Dave Young wrote:
> Jan Stodola <jstodola at redhat.com> reported ppc64 root= is always added in kexec
> kernel cmdline. But sometimes we need boot without root= for example we use
> kexec to boot into installation initramfs image like below:
> kexec --load vmlinuz --initrd=initrd.img --command-line=\
> "inst.repo=http://<server>/<path>/Server/ppc64le/os/"
> 
> While creating dtb, in case there's no root= in user provided cmdline params 
> kexec-tools will find the original root= param used in 1st kernel and pass it
> to 2nd kernel. This caused that user have no way to remove root= cmdline.
> 
> Dropping that part of code so that one can get chance to kexec into 2nd kernel
> without root= param. One can still provide root= in --command-line=""

I'm a little concerned about the backwards-compatibility implications of
this change. Though I agree the new behaviour is entirely sane perhaps
it should be activated via a new command line option.

Also, won't this affect other architectures that use DT.
I'm thinking about ARM. If so it might be good to tweak the changelog.