Date:   Tue, 14 Mar 2023 22:22:54 +0800
From:   Baoquan He <bhe@redhat.com>
To:     Eric DeVolder <eric.devolder@oracle.com>
Cc:     linux-kernel@vger.kernel.org, x86@kernel.org,
        kexec@lists.infradead.org, ebiederm@xmission.com,
        dyoung@redhat.com, vgoyal@redhat.com, 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,
        sourabhjain@linux.ibm.com, konrad.wilk@oracle.com,
        boris.ostrovsky@oracle.com
Subject: Re: [PATCH v19 2/7] crash: add generic infrastructure for crash
 hotplug support
Message-ID: <ZBCDPuTdjMY+7VrG@MiWiFi-R3L-srv>
References: <20230306162228.8277-1-eric.devolder@oracle.com>
 <20230306162228.8277-3-eric.devolder@oracle.com>
 <ZBBPzKBTuzGZe4OC@MiWiFi-R3L-srv>
 <2fd31764-b341-638a-f70e-43dc0d5b0092@oracle.com>
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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.