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kdump, documentation: describe craskernel CMA reservation

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

Link: https://lkml.kernel.org/r/aEqpQwUy6gqSiUkV@dwarf.suse.cz
Signed-off-by: Jiri 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: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Jiri Bohac 2025-06-12 12:17:39 +02:00 • committed by Andrew Morton
parent ab475510e0
commit ce1bf19a34
2 changed files with 43 additions and 0 deletions
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21
Documentation/admin-guide/kdump/kdump.rst
View file

@ -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

22
Documentation/admin-guide/kernel-parameters.txt
View file

@ -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