linux-kernel - Re: [PATCH v13 7/7] x86/crash: add x86 crash hotplug support

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Message-ID: <c08bb557-846c-0f82-391a-3eeda7e6ea67@oracle.com>
Date:   Wed, 2 Nov 2022 11:54:08 -0500
From:   Eric DeVolder <eric.devolder@...cle.com>
To:     Borislav Petkov <bp@...en8.de>
Cc:     linux-kernel@...r.kernel.org, x86@...nel.org,
        kexec@...ts.infradead.org, ebiederm@...ssion.com,
        dyoung@...hat.com, bhe@...hat.com, vgoyal@...hat.com,
        tglx@...utronix.de, mingo@...hat.com, 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 v13 7/7] x86/crash: add x86 crash hotplug support



On 11/2/22 11:19, Borislav Petkov wrote:
> On Wed, Nov 02, 2022 at 09:55:06AM -0500, Eric DeVolder wrote:
>>> "But on a plain simple laptop or workstation which has CPU hotplug,
>>> would it make sense for the crash ranges to get updated too when CPUs
>>> are offlined?
>>
>> Yes, it does.
> 
> Why?
> 

Technically the answer is no; cpu hotplug events are independent of memory hotplug events, but both 
are written into the elfcorehdr, so in reality yes... The elfcorehdr contains a single list of Phdrs 
describing CPUs and crash memory ranges; the entire list is re-written on a hotplug change.

Eric