some questions about elf_ppc64_load

[liu.song11 at zte.com.cn]

Laurent Dufour <ldufour at linux.vnet.ibm.com> wrote on 2015-01-06 18:00:07:

> From: Laurent Dufour <ldufour at linux.vnet.ibm.com>
> To: liu.song11 at zte.com.cn,
> Cc: kexec at lists.infradead.org
> Date: 2015-01-06 18:00
> Subject: Re: some questions about elf_ppc64_load
>
> On 06/01/2015 10:20, liu.song11 at zte.com.cn wrote:
> >
> >
> > Laurent Dufour <ldufour at linux.vnet.ibm.com> wrote on 2015-01-06 16:37:03:
> >
> >> From: Laurent Dufour <ldufour at linux.vnet.ibm.com>
> >> To: liu.song11 at zte.com.cn,
> >> Cc: kexec at lists.infradead.org
> >> Date: 2015-01-06 16:37
> >> Subject: Re: some questions about elf_ppc64_load
> >>
> >> On 06/01/2015 07:44, liu.song11 at zte.com.cn wrote:
> >>>
> >>> hi all，
> >>>
> >>> I use kexec-tools-2.0.8 for ppc64, in fuction elf_ppc64_load prompt "Can't use ramdisk with device tree blob input".
> >>>
> >>> I don't know why here ramdisk can't together with dtb,and need some help.
> >>
> >> The device tree is also specifying initrd (see kexec/fs2dt.c putnode),
> >> so there is 2 initrd specify in that case. The code is a bit rough here,
> >> but I guess this is because there is not yet a valid use case.
> > hi Cheers,
> > In "elf_ppc64_load", if we haven't assign a special dtb by --dtb=<filename>, then here will use "create_flatten_tree" to
> > create one. However, My board need assign a dtb, so I use --dtb=my.dtb to assign it. The dtb file is valid which I use it
> > to start kernel under uboot. For now, I just confuse is why the "create_flatten_tree" create dtb could work, but I assigned
> > dtb couldn't, my.dtb is 40KB and smaller than create dtb's 76KB. The two ways both use add_buffer with param "buf_end = -1",
> > so will add segment for the top of the valid mem range, and my.dtb is smaller which less chance of overlap some data in memory.
>
> The service create_flatten_tree create a DTB from the one inherited at
> the boot time of the currently running kernel (/proc/device-tree). I
> guess this device tree is valid since the current kernel is running ;)
>
> You may try to see what the device tree passed to your kexed kernel is,
> may be there is something wrong there. Also looking at what going wrong
> when the kexed kernel is panicing may be helpful.
>
> Cheers,
> Laurent.
>
Thanks Laurent, the dtb which I used is invalid for kexec a kernel, this dtb just used in u-boot and it would be processed by u-boot,
then it could fit to kernel's require.

Thanks
Regards

> >
> >>
> >>> I also have some questions, when I just ./kexe -l vmlinux then ./kexec -e, will jump to second kernel sucessfully,
> >>>
> >>> but without useful dtb, then device can't init correct. But, when I input ./kexec -l vmlinux --dtb=my.dtb , then
> >>>
> >>> ./kexec -e, the kernel couldn't work and crash in head_64.S, this problem also make me confused.
> >>
> >> It's hard to state with no more details. I guess the device tree blob
> >> you're using is not valid, or contain bad data.
> >>
> >> Cheers,
> >> Laurent.
> >>
> >>> Thanks
> >>> Regards
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