linux-kernel - Re: [PATCH v19 2/7] crash: add generic infrastructure for crash hotplug support

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Date:   Tue, 14 Mar 2023 22:22:54 +0800
From:   Baoquan He <bhe@...hat.com>
To:     Eric DeVolder <eric.devolder@...cle.com>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, ebiederm@...ssion.com,
        dyoung@...hat.com, vgoyal@...hat.com, tglx@...utronix.de,
        mingo@...hat.com, bp@...en8.de, dave.hansen@...ux.intel.com,
        hpa@...or.com, nramas@...ux.microsoft.com, thomas.lendacky@....com,
        robh@...nel.org, efault@....de, rppt@...nel.org, david@...hat.com,
        sourabhjain@...ux.ibm.com, konrad.wilk@...cle.com,
        boris.ostrovsky@...cle.com
Subject: Re: [PATCH v19 2/7] crash: add generic infrastructure for crash
 hotplug support

On 03/14/23 at 08:28am, Eric DeVolder wrote:
......
> > > +static int crash_memhp_notifier(struct notifier_block *nb, unsigned long val, void *v)
> > > +{
> > > +	switch (val) {
> > > +	case MEM_ONLINE:
> > > +		crash_handle_hotplug_event(KEXEC_CRASH_HP_ADD_MEMORY,
> > > +			KEXEC_CRASH_HP_INVALID_CPU);
> > > +		break;
> > > +
> > > +	case MEM_OFFLINE:
> > > +		crash_handle_hotplug_event(KEXEC_CRASH_HP_REMOVE_MEMORY,
> > > +			KEXEC_CRASH_HP_INVALID_CPU);
> > > +		break;
> > > +	}
> > > +	return NOTIFY_OK;
> > > +}
> > > +
> > > +static struct notifier_block crash_memhp_nb = {
> > > +	.notifier_call = crash_memhp_notifier,
> > > +	.priority = 0
> > > +};
> > > +
> > 
> > Because for_each_possible_cpu() is taken in
> > crash_prepare_elf64_headers(), x86 doesn't need to respond to cpu
> > hotplug or doesn't do anything with this patchset. This cpu part in
> > infrastructure is only for the later powerpc usage, right?
> 
> That is true, yes.

Given this patchset is aimed at crash hotplug on x86, while obviously it
does't need to have the cpu hotplug support on x86 since the
for_each_possible_cpu() adjustment. People looking into this may be
confused if they don't follow the discussion thread of v18. Do we need
to mention this in cover letter or somewhere else? I could miss that
though it is has been told, please ignore this if yes.