kexec: split crashkernel reservation code out from crash_core.c

Patch series "Split crash out from kexec and clean up related config
items", v3.

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@intel.com/

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.


This patch (of 14):

Both kdump and fa_dump of ppc rely on crashkernel reservation.  Move the
relevant codes into separate files: crash_reserve.c,
include/linux/crash_reserve.h.

And also add config item CRASH_RESERVE to control its enabling of the
codes.  And update config items which has relationship with crashkernel
reservation.

And also change ifdeffery from CONFIG_CRASH_CORE to CONFIG_CRASH_RESERVE
when those scopes are only crashkernel reservation related.

And also rename arch/XXX/include/asm/{crash_core.h => crash_reserve.h} on
arm64, x86 and risc-v because those architectures' crash_core.h is only
related to crashkernel reservation.

[akpm@linux-foundation.org: s/CRASH_RESEERVE/CRASH_RESERVE/, per Klara Modin]
Link: https://lkml.kernel.org/r/20240124051254.67105-1-bhe@redhat.com
Link: https://lkml.kernel.org/r/20240124051254.67105-2-bhe@redhat.com
Signed-off-by: Baoquan He <bhe@redhat.com>
Acked-by: Hari Bathini <hbathini@linux.ibm.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Cc: Eric W. Biederman <ebiederm@xmission.com>
Cc: Pingfan Liu <piliu@redhat.com>
Cc: Klara Modin <klarasmodin@gmail.com>
Cc: Michael Kelley <mhklinux@outlook.com>
Cc: Nathan Chancellor <nathan@kernel.org>
Cc: Stephen Rothwell <sfr@canb.auug.org.au>
Cc: Yang Li <yang.lee@linux.alibaba.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

8 files changed, 13 insertions, 12 deletions

diff --git a/arch/arm64/Kconfig b/arch/arm64/Kconfig
index 386566138620..5a7ac1f37bdc 100644
--- a/arch/arm64/Kconfig
+++ b/arch/arm64/Kconfig
@@ -1519,7 +1519,7 @@ config ARCH_SUPPORTS_CRASH_DUMP
 	def_bool y
 
 config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
-	def_bool CRASH_CORE
+	def_bool CRASH_RESERVE
 
 config TRANS_TABLE
 	def_bool y
diff --git a/arch/arm64/include/asm/crash_core.h b/arch/arm64/include/asm/crash_reserve.h
index 9f5c8d339f44..4afe027a4e7b 100644
--- a/arch/arm64/include/asm/crash_core.h
+++ b/arch/arm64/include/asm/crash_reserve.h
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
-#ifndef _ARM64_CRASH_CORE_H
-#define _ARM64_CRASH_CORE_H
+#ifndef _ARM64_CRASH_RESERVE_H
+#define _ARM64_CRASH_RESERVE_H
 
 /* Current arm64 boot protocol requires 2MB alignment */
 #define CRASH_ALIGN                     SZ_2M
diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig
index b9fc064d38d2..7f704ae5c5ef 100644
--- a/arch/powerpc/Kconfig
+++ b/arch/powerpc/Kconfig
@@ -691,6 +691,7 @@ config FA_DUMP
 	bool "Firmware-assisted dump"
 	depends on PPC64 && (PPC_RTAS || PPC_POWERNV)
 	select CRASH_CORE
+	select CRASH_RESERVE
 	select CRASH_DUMP
 	help
 	  A robust mechanism to get reliable kernel crash dump with
diff --git a/arch/powerpc/mm/nohash/kaslr_booke.c b/arch/powerpc/mm/nohash/kaslr_booke.c
index b4f2786a7d2b..cdff129abb14 100644
--- a/arch/powerpc/mm/nohash/kaslr_booke.c
+++ b/arch/powerpc/mm/nohash/kaslr_booke.c
@@ -13,7 +13,7 @@
 #include <linux/delay.h>
 #include <linux/memblock.h>
 #include <linux/libfdt.h>
-#include <linux/crash_core.h>
+#include <linux/crash_reserve.h>
 #include <linux/of.h>
 #include <linux/of_fdt.h>
 #include <asm/cacheflush.h>
@@ -173,7 +173,7 @@ static __init bool overlaps_region(const void *fdt, u32 start,
 
 static void __init get_crash_kernel(void *fdt, unsigned long size)
 {
-#ifdef CONFIG_CRASH_CORE
+#ifdef CONFIG_CRASH_RESERVE
 	unsigned long long crash_size, crash_base;
 	int ret;
 
diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
index bffbd869a068..bd06ad1bb97c 100644
--- a/arch/riscv/Kconfig
+++ b/arch/riscv/Kconfig
@@ -767,7 +767,7 @@ config ARCH_SUPPORTS_CRASH_DUMP
 	def_bool y
 
 config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
-	def_bool CRASH_CORE
+	def_bool CRASH_RESERVE
 
 config COMPAT
 	bool "Kernel support for 32-bit U-mode"
diff --git a/arch/riscv/include/asm/crash_core.h b/arch/riscv/include/asm/crash_reserve.h
index e1874b23feaf..013962e63587 100644
--- a/arch/riscv/include/asm/crash_core.h
+++ b/arch/riscv/include/asm/crash_reserve.h
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0-only */
-#ifndef _RISCV_CRASH_CORE_H
-#define _RISCV_CRASH_CORE_H
+#ifndef _RISCV_CRASH_RESERVE_H
+#define _RISCV_CRASH_RESERVE_H
 
 #define CRASH_ALIGN			PMD_SIZE
 
diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
index 5edec175b9bf..5bd925815154 100644
--- a/arch/x86/Kconfig
+++ b/arch/x86/Kconfig
@@ -2106,7 +2106,7 @@ config ARCH_SUPPORTS_CRASH_HOTPLUG
 	def_bool y
 
 config ARCH_HAS_GENERIC_CRASHKERNEL_RESERVATION
-	def_bool CRASH_CORE
+	def_bool CRASH_RESERVE
 
 config PHYSICAL_START
 	hex "Physical address where the kernel is loaded" if (EXPERT || CRASH_DUMP)
diff --git a/arch/x86/include/asm/crash_core.h b/arch/x86/include/asm/crash_reserve.h
index 76af98f4e801..152239f95541 100644
--- a/arch/x86/include/asm/crash_core.h
+++ b/arch/x86/include/asm/crash_reserve.h
@@ -1,6 +1,6 @@
 /* SPDX-License-Identifier: GPL-2.0 */
-#ifndef _X86_CRASH_CORE_H
-#define _X86_CRASH_CORE_H
+#ifndef _X86_CRASH_RESERVE_H
+#define _X86_CRASH_RESERVE_H
 
 /* 16M alignment for crash kernel regions */
 #define CRASH_ALIGN             SZ_16M
@@ -39,4 +39,4 @@ static inline unsigned long crash_low_size_default(void)
 #endif
 }
 
-#endif /* _X86_CRASH_CORE_H */
+#endif /* _X86_CRASH_RESERVE_H */