On 02/02/24 at 10:53am, Hari Bathini wrote: > Hi Baoquan, > > On 19/01/24 8:22 pm, Baoquan He wrote: > > 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 9 arch-es > > which support crash dumping; > > > > 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 > > FA_DUMP also needs PROC_VMCORE (CRASH_DUMP by dependency, I guess). > So, the FA_DUMP related changes here will need a relook.. Thanks for checking this. So FA_DUMP needs vmcoreinfo exporting, crashkernel reservation, /proc/vmcore. Then it's easy to adjust the kernel config item of FA_DUMP to make it select CRASH_DUMP. Except of this, do you have concern about the current code and Kconfig refactorying? ---->VMCORE_INFO /| FA_DUMP--> CRASH_DUMP-->/-|---->CRASH_RESERVE \ | \---->PROC_VMCORE > > > > ---->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. Let me 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. > > On powerpc, both kdump and fadump need PROC_VMCORE & CRASH_DUMP. > Hope that clears things. So, patch 3/14 breaks things for FA_DUMP.. I see it now. We can easily fix that with below patch. What do you think? By the way, do you have chance to help test these on powerpc system? I can find ppc64le machine, while I don't know how to operate to test fadump. >From fa8e6c3930d4f22f2b3768399c5bf0523c17adde Mon Sep 17 00:00:00 2001 From: Baoquan He <bhe@xxxxxxxxxx> Date: Sun, 4 Feb 2024 11:06:54 +0800 Subject: [PATCH] power/fadump: make FA_DUMP select CRASH_DUMP Content-type: text/plain FA_DUMP which is similar with kdump needs vmcoreinfo exporting, crashkernel reservation and /proc/vmcore file . After refactoring crash related codes and Kconfig items, make FA_DUMP select CRASH_DUMP. Now the dependency layout is like below: ---->VMCORE_INFO /| FA_DUMP--> CRASH_DUMP-->/-|---->CRASH_RESERVE \ | \---->PROC_VMCORE Signed-off-by: Baoquan He <bhe@xxxxxxxxxx> --- arch/powerpc/Kconfig | 3 +-- 1 file changed, 1 insertion(+), 2 deletions(-) diff --git a/arch/powerpc/Kconfig b/arch/powerpc/Kconfig index f182fb354bef..d5d4c890f010 100644 --- a/arch/powerpc/Kconfig +++ b/arch/powerpc/Kconfig @@ -695,8 +695,7 @@ config ARCH_SELECTS_CRASH_DUMP config FA_DUMP bool "Firmware-assisted dump" depends on PPC64 && (PPC_RTAS || PPC_POWERNV) - select VMCORE_INFO - select CRASH_RESERVE + select CRASH_DUMP help A robust mechanism to get reliable kernel crash dump with assistance from firmware. This approach does not use kexec, -- 2.41.0 > > > 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. > > > Sure. I will take a closer look... Thanks a lot. Please feel free to post patches to make that, or I can do it with your support or suggestion.
