On 2/9/23 13:10, Sourabh Jain wrote:
Hello Eric, On 01/02/23 04:12, Eric DeVolder wrote:To support crash hotplug, a mechanism is needed to update the crash elfcorehdr upon CPU or memory changes (eg. hot un/plug or off/ onlining). To track CPU changes, callbacks are registered with the cpuhp mechanism via cpuhp_setup_state_nocalls(CPUHP_BP_PREPARE_DYN). The crash hotplug elfcorehdr update has no explicit ordering requirement (relative to other cpuhp states), so meets the criteria for utilizing CPUHP_BP_PREPARE_DYN. CPUHP_BP_PREPARE_DYN is a dynamic state and avoids the need to introduce a new state for crash hotplug. Also, this is the last state in the PREPARE group, just prior to the STARTING group, which is very close to the CPU starting up in an plug/online situation, or stopping in a unplug/ offline situation. This minimizes the window of time during an actual plug/online or unplug/offline situation in which the elfcorehdr would be inaccurate. Note, that when a CPU is being unplugged/offlined, the CPU is still in the foreach_present_cpu() during the regeneration of the elfcorehdr. Thus there is a need to explicitly check and exclude the soon-to-be offlined CPU. See patch 'kexec: exclude hot remove cpu from elfcorehdr notes'. To track memory changes, a notifier is registered to capture the memblock MEM_ONLINE and MEM_OFFLINE events via register_memory_notifier(). The cpu callbacks and memory notifiers invoke handle_hotplug_event() which performs needed tasks and then dispatches the event to the architecture specific arch_crash_handle_hotplug_event() to update the elfcorehdr with the current state of CPUs and memory. During the process, the kexec_lock is held. Signed-off-by: Eric DeVolder <eric.devolder@xxxxxxxxxx> Acked-by: Baoquan He <bhe@xxxxxxxxxx> --- include/linux/crash_core.h | 9 +++ include/linux/kexec.h | 12 ++++ kernel/crash_core.c | 139 +++++++++++++++++++++++++++++++++++++ 3 files changed, 160 insertions(+) diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h index de62a722431e..ed868d237c07 100644 --- a/include/linux/crash_core.h +++ b/include/linux/crash_core.h @@ -84,4 +84,13 @@ int parse_crashkernel_high(char *cmdline, unsigned long long system_ram, int parse_crashkernel_low(char *cmdline, unsigned long long system_ram, unsigned long long *crash_size, unsigned long long *crash_base); +#define KEXEC_CRASH_HP_NONE 0 +#define KEXEC_CRASH_HP_REMOVE_CPU 1 +#define KEXEC_CRASH_HP_ADD_CPU 2 +#define KEXEC_CRASH_HP_REMOVE_MEMORY 3 +#define KEXEC_CRASH_HP_ADD_MEMORY 4 +#define KEXEC_CRASH_HP_INVALID_CPU -1U + +struct kimage; + #endif /* LINUX_CRASH_CORE_H */ diff --git a/include/linux/kexec.h b/include/linux/kexec.h index 27ef420c7a45..a52624ae4452 100644 --- a/include/linux/kexec.h +++ b/include/linux/kexec.h @@ -33,6 +33,7 @@ extern note_buf_t __percpu *crash_notes; #include <linux/compat.h> #include <linux/ioport.h> #include <linux/module.h> +#include <linux/highmem.h> #include <asm/kexec.h> /* Verify architecture specific macros are defined */ @@ -371,6 +372,13 @@ struct kimage { struct purgatory_info purgatory_info; #endif +#ifdef CONFIG_CRASH_HOTPLUG + int hp_action; + unsigned int offlinecpu; + bool elfcorehdr_index_valid; + int elfcorehdr_index;May be I am reiterating myself but I think we can manage without elfcorehdr_index_valid. Here is how: Initialize the elfcorehdr_index with a negative value in do_kimage_alloc_init function (it is called for both kexec_load and kexec_file_load). Now when the control reaches to handle_hotplug_event function and if elfcorehdr_index has negative value find the correct index and re-initialize the elfcorehdr_index. Thoughts? Thanks, Sourabh Jain
ok, I'll eliminate elfcorehdr_index_valid. eric _______________________________________________ kexec mailing list kexec@xxxxxxxxxxxxxxxxxxx http://lists.infradead.org/mailman/listinfo/kexec
