Re: [edk2-devel] How /sys/firmware/fdt getting created

["dann frazier" <dann.frazier@canonical.com>]

On Fri, Nov 01, 2019 at 10:17:30AM +0530, Prabhakar Kushwaha wrote:
> On Fri, Nov 1, 2019 at 2:04 AM dann frazier <dann.frazier@canonical.com> wrote:
> >
> > On Thu, Oct 31, 2019 at 12:55:10PM -0600, dann frazier wrote:
> > > On Thu, Oct 31, 2019 at 6:16 AM Leif Lindholm <leif.lindholm@linaro.org> wrote:
> > > >
> > > > On Thu, Oct 31, 2019 at 11:07:52AM +0100, Laszlo Ersek wrote:
> > > > > +Leif, comment at bottom
> > > >
> > > > Thanks Laszlo. +Dann, -kexec.
> > > >
> > > > > On 10/30/19 09:16, Prabhakar Kushwaha wrote:
> > > > > >> So if you want to add these properties, you should add them there.
> > > > > >>
> > > > > >> Can you explain why doing this is necessary?
> > > > > >
> > > > > > I am trying to test kexec -p (kdump feature) on CentOS-release
> > > > > > 7.7.1908 and Ubuntu-18.04 distributions.
> > > > > >
> > > > > >  "kexec -p" command show error on Ubuntu. While no error on CentOS
> > > > > >
> > > > > > CentOS:
> > > > > > $ kexec -p /boot/vmlinuz-`uname -r` --initrd=/boot/initramfs-`uname
> > > > > > -r`.img --reuse-cmdline
> > > > > > $    ==> No error
> > > > > >
> > > > > > Ubuntu
> > > > > > $ kexec -p /boot/vmlinuz-`uname -r` --initrd=/boot/initrd.img-`uname
> > > > > > -r` --reuse-cmdline
> > > > > > $ kexec: elfcorehdr doesn't fit cells-size.
> > > > > > $ kexec: setup_2nd_dtb failed.
> > > > > > $ kexec: load failed.
> > > > > > $ Cannot load /boot/vmlinuz-5.4.0-rc4+
> > > > > >
> > > > > > Note: Both CentOS and Ubuntu has Linux-5.4-rc4 tag.
> > > > > >
> > > > > > When i debugged further reason for Ubuntu error is due to
> > > > > > address-cells and size-cells as "1"
> > > > > > log from kexec tool :-
> > > > > > load_crashdump_segments: elfcorehdr 0x7f7cbfc000-0x7f7cbff7ff
> > > > > > read_1st_dtb: found name =dtb_sys  /sys/firmware/fdt
> > > > > > get_cells_size: #address-cells:1 #size-cells:1
> > > > > >
> > > > > > On CentOS both values are "2".
> > > > > > log from kexec tool :-
> > > > > > load_crashdump_segments: elfcorehdr 0xbf98bf0000-0xbf98bf33ff
> > > > > > read_1st_dtb: found nmae=dtb_sys /sys/firmware/fdt
> > > > > > get_cells_size: #address-cells:2 #size-cells:2
> > > > > >
> > > > > > Note: Kexec tool read values from /sys/firmware/fdt.
> > > > > >
> > > > > > I am trying to figure out why 2 distributions showing different values.
> > > > >
> > > > > http://git.savannah.gnu.org/cgit/grub.git/commit/?id=347210a5d5ce655b95315f320faa515afb723c11
> > > > >
> > > > > Ubuntu probably ships a grub version that lacks this commit.
> > > >
> > > > Yes, it came after the 18.04 release.
> > > > Dann: given that 18.04 is LTS, would it be reasonable to cherry-pick
> > > > this grub patch? I would consider the behaviour without it to be a
> > > > bug.
> > >
> > > Leif,
> > >
> > >   Likely - I'll run some tests and get back to you...
> >
> > Can you help me understand the scenario in which the above patch is
> > required? I tested an 18.04 VM w/ AAVMF (ACPI-mode), and kexec -p
> > worked fine. I also verified that 18.04 does not carry the above patch.
> >
> 
> This issue is only visible when crashkernel region reserved beyond 4GB
> by kernel.
> I reproduced this issue by providing "crashkernel=2G" in bootargs.

Prabhakar,

Thanks. I was able to reproduce w/ crashkernel=1G@4G.

In order to get this addressed in 18.04 we'll need a LP bug to track
it - would you mind filing one at
https://bugs.launchpad.net/ubuntu/+source/grub2 and subscribing me
(lpid dannf) to it?

  -dann

> 
> if kernel is not reserving memory due to crashkernel region
> overlapping with "reserved regions", you can apply below patch.
> https://patchwork.kernel.org/patch/10144305/
> 
> Update: When I migrated ubuntu grub to 2.05 this issue is gone.
> 
> --pk