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

[Dave Young]

Hi, Simon

On 10/16/15 at 10:33am, Simon Horman wrote:
> 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.

I did not notice this problem until Jan reported it so I thouhgt that it is
just a hidden assumption, people might not notice it and use it that way.

For Fedora/RHEL kdump we will copy 1st kernel cmdline by default so one do
not need to use it. For kexec and other distributions I'm not sure..

Since it is more of a fix to original logic, personally I tend to not introducing
a new option. But if you think we need to add a new option I can do it. 

> 
> 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.

arm also uses the function, but I need verify the behavior. Will tune the changelog
after I confirming it.

Thanks
Dave