Comment 0 for bug 1728115

The linux kernel won't boot when crashkernel parameter tells it to load a crash kernel at 32Mi on ppc64el on artful.

This happens because the artful kernel is too big. In fact, multiple requirements on the architecture lead to that:

Kernel memory at address 0 is reserved.
crashkernel must be at first RMO, so architecture puts it at 128Mi. However, kdump-tools currently puts it at @32Mi because of bug https://bugs.launchpad.net/ubuntu/+source/makedumpfile/+bug/1567539.
PACA and LPPACA need to be at the first RMO as well, and with 2048 CPUs, they take more than 5MB and 2MiB, respectively.

With the kernel now taking around 25MB from stext to _end, the kernel can't reserve enough memory for PACA or LPPACA right after boot, and it panics.

So, right after installing kdump-tools on artful, and rebooting, the kernel won't boot, with no sign of life as we haven't even started any console. Investigation for this issue took an entire day.

The fix would be setting the loading address to 128MiB, and start reducing size of PACA and maybe remove some of the requirements for the location of PACA and crash kernel.

I would not even set the loading address of the crash kernel in the parameter itself, and leave it to the kernel to decide it, which it already does and already would put it at 128Mi.

Cascardo.