This gives the physical address where the kernel is loaded.

If kernel is a not relocatable (CONFIG_RELOCATABLE=n) then
bzImage will decompress itself to above physical address and
run from there. Otherwise, bzImage will run from the address where
it has been loaded by the boot loader and will ignore above physical
address.

In normal kdump cases one does not have to set/change this option
as now bzImage can be compiled as a completely relocatable image
(CONFIG_RELOCATABLE=y) and be used to load and run from a different
address. This option is mainly useful for the folks who don't want
to use a bzImage for capturing the crash dump and want to use a
vmlinux instead. vmlinux is not relocatable hence a kernel needs
to be specifically compiled to run from a specific memory area
(normally a reserved region) and this option comes handy.

So if you are using bzImage for capturing the crash dump,
leave the value here unchanged to 0x1000000 and set
CONFIG_RELOCATABLE=y. Otherwise if you plan to use vmlinux
for capturing the crash dump change this value to start of
the reserved region. In other words, it can be set based on
the "X" value as specified in the "crashkernel=YM@XM"
command line boot parameter passed to the panic-ed
kernel. Please take a look at