During a core dump, kexec creates a header to reference all the memory
blocks in the system. Previously, the kdump kernel command line supported a
"mem=" parameter that limited the memory that was dumped. When this parameter
was set, kexec could not read past the limit when creating the header, and the
dump would result in an I/O error. The "mem=" parameter has been removed
from kexec to ensure that core dumps succeed. Users of kexec should use
makedumpfile filtering to hide superfluous results.