[PATCH v7 2/8] x86/crash: Introduce new options to support cpu and memory hotplug

Eric DeVolder
2022-04-13T16:42:31Z

CRASH_HOTPLUG is to enable cpu and memory hotplug support of crash.

CRASH_HOTPLUG_ELFCOREHDR_SZ is used to specify the maximum size of
the elfcorehdr buffer/segment.

This is a preparation for later usage.

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

diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index b0142e01002e..f7b92ee1bcc7 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2072,6 +2072,32 @@ 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 a machine with up to 1024
+ CPUs and up to 1024 memory regions, eg. as represented by the
+ 'System RAM' entries in /proc/iomem.
+
config KEXEC_JUMP
bool "kexec jump"
depends on KEXEC && HIBERNATION
--
2.27.0