[PATCH v8 3/7] crash: add generic infrastructure for crash hotplug support

[Eric DeVolder]

On 5/23/22 03:36, Sourabh Jain wrote:
> Hello Eric,
> 
> On 06/05/22 00:15, Eric DeVolder wrote:
>> CPU and memory change notifications are received in order to
>> regenerate the elfcorehdr.
>>
>> To support cpu hotplug, a callback is registered to capture the
>> CPUHP_AP_ONLINE_DYN online and offline events via
>> cpuhp_setup_state_nocalls().
>>
>> To support memory hotplug, a notifier is registered to capture the
>> MEM_ONLINE and MEM_OFFLINE events via register_memory_notifier().
>>
>> The cpu callback and memory notifiers call handle_hotplug_event()
>> to handle the hot plug/unplug event. Then handle_hotplug_event()
>> dispatches the event to the architecture specific
>> arch_crash_handle_hotplug_event(). During the process, the
>> kexec_mutex is held.
>>
>> Signed-off-by: Eric DeVolder <eric.devolder at oracle.com>
>> ---
>>   include/linux/crash_core.h | 10 +++++
>>   include/linux/kexec.h      |  5 +++
>>   kernel/crash_core.c        | 92 ++++++++++++++++++++++++++++++++++++++
>>   3 files changed, 107 insertions(+)
>>
>> diff --git a/include/linux/crash_core.h b/include/linux/crash_core.h
>> index de62a722431e..a240f84348aa 100644
>> --- a/include/linux/crash_core.h
>> +++ b/include/linux/crash_core.h
>> @@ -84,4 +84,14 @@ 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_REMOVE_CPU        0
>> +#define KEXEC_CRASH_HP_ADD_CPU            1
>> +#define KEXEC_CRASH_HP_REMOVE_MEMORY    2
>> +#define KEXEC_CRASH_HP_ADD_MEMORY        3
>> +#define KEXEC_CRASH_HP_INVALID_CPU        -1U
>> +
>> +struct kimage;
>> +void arch_crash_handle_hotplug_event(struct kimage *image, unsigned int hp_action,
>> +                                    unsigned int cpu);
>> +
>>   #endif /* LINUX_CRASH_CORE_H */
>> diff --git a/include/linux/kexec.h b/include/linux/kexec.h
>> index f93f2591fc1e..5935bc78ed7f 100644
>> --- a/include/linux/kexec.h
>> +++ b/include/linux/kexec.h
>> @@ -308,6 +308,11 @@ struct kimage {
>>       struct purgatory_info purgatory_info;
>>   #endif
>> +    bool hotplug_event;
>> +    unsigned int offlinecpu;
>> +    bool elfcorehdr_index_valid;
>> +    int elfcorehdr_index;
> How about keeping above kimage elements under below config?
> #if defined(CONFIG_HOTPLUG_CPU) || defined(CONFIG_MEMORY_HOTPLUG)
> 
> Thanks,
> Sourabh Jain

Yes, of course.
Eric