Commit ce1bf19a authored by Jiri Bohac's avatar Jiri Bohac Committed by Andrew Morton
Browse files

kdump, documentation: describe craskernel CMA reservation 

Describe the new crashkernel ",cma" suffix in Documentation/

Link: https://lkml.kernel.org/r/aEqpQwUy6gqSiUkV@dwarf.suse.cz


Signed-off-by: default avatarJiri Bohac <jbohac@suse.cz>
Cc: Baoquan He <bhe@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: David Hildenbrand <david@redhat.com>
Cc: Donald Dutile <ddutile@redhat.com>
Cc: Michal Hocko <mhocko@suse.cz>
Cc: Philipp Rudo <prudo@redhat.com>
Cc: Pingfan Liu <piliu@redhat.com>
Cc: Tao Liu <ltao@redhat.com>
Cc: Vivek Goyal <vgoyal@redhat.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent ab475510

Documentation/admin-guide/kdump/kdump.rst

+21 −0
Original line number Diff line number Diff line
@@ -311,6 +311,27 @@ crashkernel syntax 


            crashkernel=0,low



4) crashkernel=size,cma



	Reserve additional crash kernel memory from CMA. This reservation is

	usable by the first system's userspace memory and kernel movable

	allocations (memory balloon, zswap). Pages allocated from this memory

	range will not be included in the vmcore so this should not be used if

	dumping of userspace memory is intended and it has to be expected that

	some movable kernel pages may be missing from the dump.



	A standard crashkernel reservation, as described above, is still needed

	to hold the crash kernel and initrd.



	This option increases the risk of a kdump failure: DMA transfers

	configured by the first kernel may end up corrupting the second

	kernel's memory.



	This reservation method is intended for systems that can't afford to

	sacrifice enough memory for standard crashkernel reservation and where

	less reliable and possibly incomplete kdump is preferable to no kdump at

	all.



Boot into System Kernel

-----------------------

1) Update the boot loader (such as grub, yaboot, or lilo) configuration

Documentation/admin-guide/kernel-parameters.txt

+22 −0
Original line number Diff line number Diff line
@@ -986,6 +986,28 @@ 
			0: to disable low allocation.

			It will be ignored when crashkernel=X,high is not used

			or memory reserved is below 4G.

	crashkernel=size[KMG],cma

			[KNL, X86] Reserve additional crash kernel memory from

			CMA. This reservation is usable by the first system's

			userspace memory and kernel movable allocations (memory

			balloon, zswap). Pages allocated from this memory range

			will not be included in the vmcore so this should not

			be used if dumping of userspace memory is intended and

			it has to be expected that some movable kernel pages

			may be missing from the dump.



			A standard crashkernel reservation, as described above,

			is still needed to hold the crash kernel and initrd.



			This option increases the risk of a kdump failure: DMA

			transfers configured by the first kernel may end up

			corrupting the second kernel's memory.



			This reservation method is intended for systems that

			can't afford to sacrifice enough memory for standard

			crashkernel reservation and where less reliable and

			possibly incomplete kdump is preferable to no kdump at

			all.



	cryptomgr.notests

			[KNL] Disable crypto self-tests