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charset="us-ascii"; Format="flowed" Sender: "kexec" Errors-To: kexec-bounces+kexec=archiver.kernel.org@lists.infradead.org On 4/23/23 05:52, Sourabh Jain wrote: > The Problem: > ============ > Post CPU/Memory hot plug/unplug and online/offline events the kernel > holds stale information about the system. Dump collection with stale > kdump kernel might end up in dump capture failure or an inaccurate dump > collection. > > Existing solution: > ================== > The existing solution to keep the kdump kernel up-to-date by monitoring > CPU/Memory hotplug/online/offline events via udev rule and trigger a full > kdump kernel reload for every hotplug event. > > Shortcomings: > ------------------------------------------------ > - Leaves a window where kernel crash might not lead to a successful dump > collection. > - Reloading all kexec components for each hotplug is inefficient. > - udev rules are prone to races if hotplug events are frequent. > > More about issues with an existing solution is posted here: > - https://lkml.org/lkml/2020/12/14/532 > - https://lists.ozlabs.org/pipermail/linuxppc-dev/2022-February/240254.html > > Proposed Solution: > ================== > Instead of reloading all kexec segments on CPU/Memory hotplug/online/offline > event, this patch series focuses on updating only the relevant kexec segment. > Once the kexec segments are loaded in the kernel reserved area then an > arch-specific hotplug handler will update the relevant kexec segment based on > hotplug event type. > > Series Dependencies > ==================== > This patch series implements the crash hotplug handler on PowerPC. The generic > crash hotplug handler is introduced by https://lkml.org/lkml/2023/4/4/1136 patch > series. > > Git tree for testing: > ===================== > The below git tree has this patch series applied on top of dependent patch > series. > https://github.com/sourabhjains/linux/tree/e21-s10 > > To realise the feature the kdump udev rule must updated to avoid > reloading of kdump reload on CPU/Memory hotplug/online/offline events. > > RHEL: /usr/lib/udev/rules.d/98-kexec.rules > > -SUBSYSTEM=="cpu", ACTION=="online", GOTO="kdump_reload_cpu" > -SUBSYSTEM=="memory", ACTION=="online", GOTO="kdump_reload_mem" > -SUBSYSTEM=="memory", ACTION=="offline", GOTO="kdump_reload_mem" > +SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end" > +SUBSYSTEM=="memory", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end" > I didn't see in the patch series where you would have the equivalent to the following (needed for the sysfs crash_hotplug entries): #ifdef CONFIG_HOTPLUG_CPU static inline int crash_hotplug_cpu_support(void) { return 1; } #define crash_hotplug_cpu_support crash_hotplug_cpu_support #endif #ifdef CONFIG_MEMORY_HOTPLUG static inline int crash_hotplug_memory_support(void) { return 1; } #define crash_hotplug_memory_support crash_hotplug_memory_support #endif > Note: only kexec_file_load syscall will work. For kexec_load minor changes are > required in kexec tool. > > --- > Changelog: > > v10: > - Drop the patch that adds fdt_index attribute to struct kimage_arch > Find the fdt segment index when needed. > - Added more details into commits messages. > - Rebased onto 6.3.0-rc5 > > v9: > - Removed patch to prepare elfcorehdr crash notes for possible CPUs. > The patch is moved to generic patch series that introduces generic > infrastructure for in kernel crash update. > - Removed patch to pass the hotplug action type to the arch crash > hotplug handler function. The generic patch series has introduced > the hotplug action type in kimage struct. > - Add detail commit message for better understanding. > > v8: > - Restrict fdt_index initialization to machine_kexec_post_load > it work for both kexec_load and kexec_file_load.[3/8] Laurent Dufour > > - Updated the logic to find the number of offline core. [6/8] > > - Changed the logic to find the elfcore program header to accommodate > future memory ranges due memory hotplug events. [8/8] > > v7 > - added a new config to configure this feature > - pass hotplug action type to arch specific handler > > v6 > - Added crash memory hotplug support > > v5: > - Replace COFNIG_CRASH_HOTPLUG with CONFIG_HOTPLUG_CPU. > - Move fdt segment identification for kexec_load case to load path > instead of crash hotplug handler > - Keep new attribute defined under kimage_arch to track FDT segment > under CONFIG_HOTPLUG_CPU config. > > v4: > - Update the logic to find the additional space needed for hotadd CPUs post > kexec load. Refer "[RFC v4 PATCH 4/5] powerpc/crash hp: add crash hotplug > support for kexec_file_load" patch to know more about the change. > - Fix a couple of typo. > - Replace pr_err to pr_info_once to warn user about memory hotplug > support. > - In crash hotplug handle exit the for loop if FDT segment is found. > > v3 > - Move fdt_index and fdt_index_vaild variables to kimage_arch struct. > - Rebase patche on top of https://lkml.org/lkml/2022/3/3/674 [v5] > - Fixed warning reported by checpatch script > > v2: > - Use generic hotplug handler introduced by https://lkml.org/lkml/2022/2/9/1406, a > significant change from v1. > > Sourabh Jain (5): > powerpc/kexec: turn some static helper functions public > powerpc/crash: introduce a new config option CRASH_HOTPLUG > powerpc/crash: add crash CPU hotplug support > crash: forward memory_notify args to arch crash hotplug handler > powerpc/kexec: add crash memory hotplug support > > arch/powerpc/Kconfig | 12 + > arch/powerpc/include/asm/kexec.h | 10 + > arch/powerpc/include/asm/kexec_ranges.h | 1 + > arch/powerpc/kexec/core_64.c | 301 ++++++++++++++++++++++++ > arch/powerpc/kexec/elf_64.c | 12 +- > arch/powerpc/kexec/file_load_64.c | 212 ++++------------- > arch/powerpc/kexec/ranges.c | 85 +++++++ > arch/x86/include/asm/kexec.h | 2 +- > arch/x86/kernel/crash.c | 3 +- > include/linux/kexec.h | 2 +- > kernel/crash_core.c | 14 +- > 11 files changed, 479 insertions(+), 175 deletions(-) > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec