From: Jiri Bohac Date: Thu, 12 Jun 2025 10:17:39 +0000 (+0200) Subject: kdump, documentation: describe craskernel CMA reservation X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=ce1bf19a34dfa1f418037cebe11f5d2c7adf9d1e;p=thirdparty%2Flinux.git 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: Jiri Bohac Cc: Baoquan He Cc: Dave Young Cc: David Hildenbrand Cc: Donald Dutile Cc: Michal Hocko Cc: Philipp Rudo Cc: Pingfan Liu Cc: Tao Liu Cc: Vivek Goyal Signed-off-by: Andrew Morton --- diff --git a/Documentation/admin-guide/kdump/kdump.rst b/Documentation/admin-guide/kdump/kdump.rst index 20fabdf6567e1..9c6cd52f69cf7 100644 --- a/Documentation/admin-guide/kdump/kdump.rst +++ b/Documentation/admin-guide/kdump/kdump.rst @@ -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 diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index f1f2c0874da9d..ac4a239b9388c 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt @@ -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