linux-kernel - Re: [PATCH v12 7/7] x86/crash: Add x86 crash hotplug support

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Message-ID: <Y1w76RwZUKUvsS7A@zn.tnic>
Date:   Fri, 28 Oct 2022 22:30:33 +0200
From:   Borislav Petkov <bp@...en8.de>
To:     Eric DeVolder <eric.devolder@...cle.com>
Cc:     Baoquan He <bhe@...hat.com>, david@...hat.com,
        Oscar Salvador <osalvador@...e.de>,
        Andrew Morton <akpm@...ux-foundation.org>,
        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, dave.hansen@...ux.intel.com, hpa@...or.com,
        nramas@...ux.microsoft.com, thomas.lendacky@....com,
        robh@...nel.org, efault@....de, rppt@...nel.org,
        sourabhjain@...ux.ibm.com, linux-mm@...ck.org
Subject: Re: [PATCH v12 7/7] x86/crash: Add x86 crash hotplug support

On Fri, Oct 28, 2022 at 02:26:58PM -0500, Eric DeVolder wrote:
> config CRASH_MAX_MEMORY_RANGES
>     depends on CRASH_DUMP && KEXEC_FILE && MEMORY_HOTPLUG
>     int
>     default 8192
>     help
>       For the kexec_file_load path, specify the maximum number of
>       memory regions, eg. as represented by the 'System RAM' entries
>       in /proc/iomem, that the elfcorehdr buffer/segment can accommodate.
>       This value is combined with NR_CPUS and multiplied by Elf64_Phdr
>       size to determine the final buffer size.

No, do this:

config CRASH_MEMORY_HOTPLUG_SUPPORT
    depends on CRASH_DUMP && KEXEC_FILE && MEMORY_HOTPLUG
    help
      Help text explaining what this feature is

this thing will simply get enabled when the user enables MEMORY_HOTPLUG
and CRASH_DUMP.

and then you do in the code:

/*
 * A comment explaining how the 8192 value has been selected.
 */
#define CRASH_MAX_MEMORY_RANGES	8192

Thx.

-- 
Regards/Gruss,
    Boris.

https://people.kernel.org/tglx/notes-about-netiquette