[PATCH linux-next v3 00/14] Split crash out from kexec and clean up related config items

From: Baoquan He
Date: Wed Jan 24 2024 - 00:13:20 EST

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Motivation:
=============
Previously, LKP reported a building error. When investigating, it can't
be resolved reasonablly with the present messy kdump config items.

https://lore.kernel.org/oe-kbuild-all/202312182200.Ka7MzifQ-lkp@xxxxxxxxx/

The kdump (crash dumping) related config items could causes confusions:

Firstly,
---
CRASH_CORE enables codes including
- crashkernel reservation;
- elfcorehdr updating;
- vmcoreinfo exporting;
- crash hotplug handling;

Now fadump of powerpc, kcore dynamic debugging and kdump all selects
CRASH_CORE, while fadump
- fadump needs crashkernel parsing, vmcoreinfo exporting, and accessing
global variable 'elfcorehdr_addr';
- kcore only needs vmcoreinfo exporting;
- kdump needs all of the current kernel/crash_core.c.

So only enabling PROC_CORE or FA_DUMP will enable CRASH_CORE, this
mislead people that we enable crash dumping, actual it's not.

Secondly,
---
It's not reasonable to allow KEXEC_CORE select CRASH_CORE.

Because KEXEC_CORE enables codes which allocate control pages, copy
kexec/kdump segments, and prepare for switching. These codes are
shared by both kexec reboot and kdump. We could want kexec reboot,
but disable kdump. In that case, CRASH_CORE should not be selected.

--------------------
CONFIG_CRASH_CORE=y
CONFIG_KEXEC_CORE=y
CONFIG_KEXEC=y
CONFIG_KEXEC_FILE=y
---------------------

Thirdly,
---
It's not reasonable to allow CRASH_DUMP select KEXEC_CORE.

That could make KEXEC_CORE, CRASH_DUMP are enabled independently from
KEXEC or KEXEC_FILE. However, w/o KEXEC or KEXEC_FILE, the KEXEC_CORE
code built in doesn't make any sense because no kernel loading or
switching will happen to utilize the KEXEC_CORE code.
---------------------
CONFIG_CRASH_CORE=y
CONFIG_KEXEC_CORE=y
CONFIG_CRASH_DUMP=y
---------------------

In this case, what is worse, on arch sh and arm, KEXEC relies on MMU,
while CRASH_DUMP can still be enabled when !MMU, then compiling error is
seen as the lkp test robot reported in above link.

------arch/sh/Kconfig------
config ARCH_SUPPORTS_KEXEC
def_bool MMU

config ARCH_SUPPORTS_CRASH_DUMP
def_bool BROKEN_ON_SMP
---------------------------

Changes:
===========
1, split out crash_reserve.c from crash_core.c;
2, split out vmcore_infoc. from crash_core.c;
3, move crash related codes in kexec_core.c into crash_core.c;
4, remove dependency of FA_DUMP on CRASH_DUMP;
5, clean up kdump related config items;
6, wrap up crash codes in crash related ifdefs on all 8 arch-es
which support crash dumping, except of ppc;

Achievement:
===========
With above changes, I can rearrange the config item logic as below (the right
item depends on or is selected by the left item):

PROC_KCORE -----------> VMCORE_INFO

|----------> VMCORE_INFO
FA_DUMP----|
|----------> CRASH_RESERVE

---->VMCORE_INFO
/
|---->CRASH_RESERVE
KEXEC --| /|
|--> KEXEC_CORE--> CRASH_DUMP-->/-|---->PROC_VMCORE
KEXEC_FILE --| \ |
\---->CRASH_HOTPLUG

KEXEC --|
|--> KEXEC_CORE (for kexec reboot only)
KEXEC_FILE --|

Test
========
On all 8 architectures, including x86_64, arm64, s390x, sh, arm, mips,
riscv, loongarch, I did below three cases of config item setting and
building all passed. Take configs on x86_64 as exampmle here:

(1) Both CONFIG_KEXEC and KEXEC_FILE is unset, then all kexec/kdump
items are unset automatically:
# Kexec and crash features
# CONFIG_KEXEC is not set
# CONFIG_KEXEC_FILE is not set
# end of Kexec and crash features

(2) set CONFIG_KEXEC_FILE and 'make olddefconfig':
---------------
# Kexec and crash features
CONFIG_CRASH_RESERVE=y
CONFIG_VMCORE_INFO=y
CONFIG_KEXEC_CORE=y
CONFIG_KEXEC_FILE=y
CONFIG_CRASH_DUMP=y
CONFIG_CRASH_HOTPLUG=y
CONFIG_CRASH_MAX_MEMORY_RANGES=8192
# end of Kexec and crash features
---------------

(3) unset CONFIG_CRASH_DUMP in case 2 and execute 'make olddefconfig':
------------------------
# Kexec and crash features
CONFIG_KEXEC_CORE=y
CONFIG_KEXEC_FILE=y
# end of Kexec and crash features
------------------------

Note:
For ppc, it needs investigation to make clear how to split out crash
code in arch folder. Hope Hari and Pingfan can help have a look, see if
it's doable. Now, I make it either have both kexec and crash enabled, or
disable both of them altogether.

Changelog
==========
v2->v3:
- In patch 2, there's conflict when rebasing to linux-next in
kernel/crash_core.c because of below commits from Uladzislau:
- commit 699d9351822e ("mm: vmalloc: Fix a warning in the crash_save_vmcoreinfo_init()")
- commit 5f4c0c1e2a51 (:mm/vmalloc: remove vmap_area_list")
- In patch 13, fix the lkp reported issue by using CONFIG_CRASH_RESERVE
ifdef, giving up the earlier IS_ENABLED(CONFIG_CRASH_RESERVE) checking in v2.
- In patch 14, update code change after below commit merged into
mainline:
- commit 78de91b45860 ("LoongArch: Use generic interface to support crashkernel=X,[high,low]")

Baoquan He (14):
kexec: split crashkernel reservation code out from crash_core.c
crash: split vmcoreinfo exporting code out from crash_core.c
crash: remove dependency of FA_DUMP on CRASH_DUMP
crash: split crash dumping code out from kexec_core.c
crash: clean up kdump related config items
x86, crash: wrap crash dumping code into crash related ifdefs
arm64, crash: wrap crash dumping code into crash related ifdefs
ppc, crash: enforce KEXEC and KEXEC_FILE to select CRASH_DUMP
s390, crash: wrap crash dumping code into crash related ifdefs
sh, crash: wrap crash dumping code into crash related ifdefs
mips, crash: wrap crash dumping code into crash related ifdefs
riscv, crash: wrap crash dumping code into crash related ifdefs
arm, crash: wrap crash dumping code into crash related ifdefs
loongarch, crash: wrap crash dumping code into crash related ifdefs

arch/arm/kernel/setup.c | 4 +-
arch/arm64/Kconfig | 2 +-
.../asm/{crash_core.h => crash_reserve.h} | 4 +-
arch/arm64/include/asm/kexec.h | 2 +-
arch/arm64/kernel/Makefile | 2 +-
arch/arm64/kernel/machine_kexec.c | 2 +-
arch/arm64/kernel/machine_kexec_file.c | 10 +-
.../kernel/{crash_core.c => vmcore_info.c} | 2 +-
arch/arm64/mm/init.c | 2 +-
arch/loongarch/kernel/setup.c | 2 +-
arch/mips/kernel/setup.c | 17 +-
arch/powerpc/Kconfig | 9 +-
arch/powerpc/kernel/setup-common.c | 2 +-
arch/powerpc/mm/nohash/kaslr_booke.c | 4 +-
arch/powerpc/platforms/powernv/opal-core.c | 2 +-
arch/riscv/Kconfig | 2 +-
.../asm/{crash_core.h => crash_reserve.h} | 4 +-
arch/riscv/kernel/Makefile | 2 +-
arch/riscv/kernel/elf_kexec.c | 9 +-
.../kernel/{crash_core.c => vmcore_info.c} | 2 +-
arch/riscv/mm/init.c | 2 +-
arch/s390/kernel/kexec_elf.c | 2 +
arch/s390/kernel/kexec_image.c | 2 +
arch/s390/kernel/machine_kexec_file.c | 10 +
arch/sh/kernel/machine_kexec.c | 3 +
arch/sh/kernel/setup.c | 2 +-
arch/x86/Kconfig | 2 +-
.../asm/{crash_core.h => crash_reserve.h} | 6 +-
arch/x86/kernel/Makefile | 6 +-
arch/x86/kernel/cpu/mshyperv.c | 4 +
arch/x86/kernel/kexec-bzimage64.c | 4 +
arch/x86/kernel/kvm.c | 4 +-
arch/x86/kernel/machine_kexec_64.c | 3 +
arch/x86/kernel/reboot.c | 2 +-
arch/x86/kernel/setup.c | 2 +-
arch/x86/kernel/smp.c | 2 +-
.../{crash_core_32.c => vmcore_info_32.c} | 2 +-
.../{crash_core_64.c => vmcore_info_64.c} | 2 +-
arch/x86/xen/enlighten_hvm.c | 4 +
drivers/base/cpu.c | 6 +-
drivers/firmware/qemu_fw_cfg.c | 14 +-
fs/proc/Kconfig | 2 +-
fs/proc/kcore.c | 2 +-
include/linux/buildid.h | 2 +-
include/linux/crash_core.h | 152 ++--
include/linux/crash_reserve.h | 48 ++
include/linux/kexec.h | 47 +-
include/linux/vmcore_info.h | 81 ++
init/initramfs.c | 2 +-
kernel/Kconfig.kexec | 12 +-
kernel/Makefile | 5 +-
kernel/crash_core.c | 762 +++++-------------
kernel/crash_reserve.c | 464 +++++++++++
kernel/{crash_dump.c => elfcorehdr.c} | 0
kernel/kexec.c | 11 +-
kernel/kexec_core.c | 250 +-----
kernel/kexec_file.c | 13 +-
kernel/kexec_internal.h | 2 +
kernel/ksysfs.c | 10 +-
kernel/printk/printk.c | 4 +-
kernel/vmcore_info.c | 231 ++++++
lib/buildid.c | 2 +-
62 files changed, 1228 insertions(+), 1043 deletions(-)
rename arch/arm64/include/asm/{crash_core.h => crash_reserve.h} (81%)
rename arch/arm64/kernel/{crash_core.c => vmcore_info.c} (97%)
rename arch/riscv/include/asm/{crash_core.h => crash_reserve.h} (78%)
rename arch/riscv/kernel/{crash_core.c => vmcore_info.c} (96%)
rename arch/x86/include/asm/{crash_core.h => crash_reserve.h} (92%)
rename arch/x86/kernel/{crash_core_32.c => vmcore_info_32.c} (90%)
rename arch/x86/kernel/{crash_core_64.c => vmcore_info_64.c} (94%)
create mode 100644 include/linux/crash_reserve.h
create mode 100644 include/linux/vmcore_info.h
create mode 100644 kernel/crash_reserve.c
rename kernel/{crash_dump.c => elfcorehdr.c} (100%)
create mode 100644 kernel/vmcore_info.c

--
2.41.0

Next message: Baoquan He: "[PATCH linux-next v3 01/14] kexec: split crashkernel reservation code out from crash_core.c"
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Next in thread: Baoquan He: "[PATCH linux-next v3 01/14] kexec: split crashkernel reservation code out from crash_core.c"
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