[PATCH v4 02/10] crash hp: Introduce CRASH_HOTPLUG configuration options

Eric DeVolder
2022-02-09T20:00:11Z

Support for CPU and memory hotplug for crash is controlled by the
CRASH_HOTPLUG configuration option, introduced by this patch.

The CRASH_HOTPLUG_ELFCOREHDR_SZ related configuration option is
also introduced with this patch.

Signed-off-by: Eric DeVolder <eric.devolder@oracle.com>
---
arch/x86/Kconfig | 26 ++++++++++++++++++++++++++
1 file changed, 26 insertions(+)

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index ebe8fc76949a..4e3374edab02 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2060,6 +2060,32 @@ config CRASH_DUMP
(CONFIG_RELOCATABLE=y).
For more details see Documentation/admin-guide/kdump/kdump.rst

+config CRASH_HOTPLUG
+ bool "kernel updates of crash elfcorehdr"
+ depends on CRASH_DUMP && (HOTPLUG_CPU || MEMORY_HOTPLUG) && KEXEC_FILE
+ help
+ Enable the kernel to update the crash elfcorehdr (which contains
+ the list of CPUs and memory regions) directly when hot plug/unplug
+ of CPUs or memory. Otherwise userspace must monitor these hot
+ plug/unplug change notifications via udev in order to
+ unload-then-reload the crash kernel so that the list of CPUs and
+ memory regions is kept up-to-date. Note that the udev CPU and
+ memory change notifications still occur (however, userspace is not
+ required to monitor for crash dump purposes).
+
+config CRASH_HOTPLUG_ELFCOREHDR_SZ
+ depends on CRASH_HOTPLUG
+ int
+ default 131072
+ help
+ Specify the maximum size of the elfcorehdr buffer/segment.
+ The 128KiB default is sized so that it can accommodate 2048
+ Elf64_Phdr, where each Phdr represents either a CPU or a
+ region of memory.
+ For example, this size can accommodate hotplugging a machine
+ with up to 1024 CPUs and up to 1024 memory regions (e.g. 1TiB
+ with 1024 1GiB memory DIMMs).
+
config KEXEC_JUMP
bool "kexec jump"
depends on KEXEC && HIBERNATION
--
2.27.0