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Message-ID: <a4b6b21a-f3f7-09cf-9d50-1706d8da7c97@oracle.com>
Date:   Mon, 23 May 2022 10:04:54 -0500
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Subject: Re: [PATCH v8 3/7] crash: add generic infrastructure for crash
 hotplug support
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To:     Sourabh Jain <sourabhjain@linux.ibm.com>,
        linux-kernel@vger.kernel.org, x86@kernel.org,
        kexec@lists.infradead.org, ebiederm@xmission.com,
        dyoung@redhat.com, bhe@redhat.com, vgoyal@redhat.com
Cc:     tglx@linutronix.de, mingo@redhat.com, bp@alien8.de,
        dave.hansen@linux.intel.com, hpa@zytor.com,
        nramas@linux.microsoft.com, thomas.lendacky@amd.com,
        robh@kernel.org, efault@gmx.de, rppt@kernel.org, david@redhat.com,
        konrad.wilk@oracle.com, boris.ostrovsky@oracle.com
References: <20220505184603.1548-1-eric.devolder@oracle.com>
 <20220505184603.1548-4-eric.devolder@oracle.com>
 <88ec248e-e00f-a84e-c652-97e49fbf2674@linux.ibm.com>
From:   Eric DeVolder <eric.devolder@oracle.com>
In-Reply-To: <88ec248e-e00f-a84e-c652-97e49fbf2674@linux.ibm.com>
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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@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