Hi Baoquan, On Wed, Jan 24, 2024 at 01:12:40PM +0800, 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 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. I am seeing a few build failures in my test matrix on next-20240125 that appear to be caused by this series although I have not bisected. Some reproduction steps: $ curl -LSso .config https://git.alpinelinux.org/aports/plain/community/linux-edge/config-edge.armv7 $ make -skj"$(nproc)" ARCH=arm CROSS_COMPILE=arm-linux-gnueabi- olddefconfig all ... arm-linux-gnueabi-ld: arch/arm/kernel/machine_kexec.o: in function `arch_crash_save_vmcoreinfo': machine_kexec.c:(.text+0x488): undefined reference to `vmcoreinfo_append_str' ... $ curl -LSso .config https://github.com/archlinuxarm/PKGBUILDs/raw/master/core/linux-aarch64/config $ make -skj"$(nproc)" ARCH=arm64 CROSS_COMPILE=aarch64-linux- olddefconfig all ... aarch64-linux-ld: kernel/kexec_file.o: in function `kexec_walk_memblock.constprop.0': kexec_file.c:(.text+0x314): undefined reference to `crashk_res' aarch64-linux-ld: kernel/kexec_file.o: relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol `crashk_res' which may bind externally can not be used when making a shared object; recompile with -fPIC kexec_file.c:(.text+0x314): dangerous relocation: unsupported relocation aarch64-linux-ld: kexec_file.c:(.text+0x318): undefined reference to `crashk_res' aarch64-linux-ld: drivers/of/kexec.o: in function `of_kexec_alloc_and_setup_fdt': kexec.c:(.text+0x580): undefined reference to `crashk_res' aarch64-linux-ld: drivers/of/kexec.o: relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol `crashk_res' which may bind externally can not be used when making a shared object; recompile with -fPIC kexec.c:(.text+0x580): dangerous relocation: unsupported relocation aarch64-linux-ld: kexec.c:(.text+0x584): undefined reference to `crashk_res' aarch64-linux-ld: kexec.c:(.text+0x590): undefined reference to `crashk_res' aarch64-linux-ld: kexec.c:(.text+0x5b0): undefined reference to `crashk_low_res' aarch64-linux-ld: drivers/of/kexec.o: relocation R_AARCH64_ADR_PREL_PG_HI21 against symbol `crashk_low_res' which may bind externally can not be used when making a shared object; recompile with -fPIC kexec.c:(.text+0x5b0): dangerous relocation: unsupported relocation aarch64-linux-ld: kexec.c:(.text+0x5b4): undefined reference to `crashk_low_res' aarch64-linux-ld: kexec.c:(.text+0x5c0): undefined reference to `crashk_low_res' ... $ curl -LSso .config https://git.alpinelinux.org/aports/plain/community/linux-edge/config-edge.x86_64 $ make -skj"$(nproc)" ARCH=x86_64 CROSS_COMPILE=x86_64-linux- olddefconfig all ... x86_64-linux-ld: arch/x86/xen/mmu_pv.o: in function `paddr_vmcoreinfo_note': mmu_pv.c:(.text+0x3af3): undefined reference to `vmcoreinfo_note' ... Cheers, Nathan
