Re: [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@xxxxxxxxxx>
> > ---
> >   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