linux-kernel - Re: [PATCH v4 02/10] crash hp: Introduce CRASH

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Message-ID: <10d67f14-c5fe-0a17-e8b5-97702823cc1c@oracle.com>
Date:   Tue, 1 Mar 2022 14:04:08 -0600
From:   Eric DeVolder <eric.devolder@...cle.com>
To:     Baoquan He <bhe@...hat.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,
        konrad.wilk@...cle.com, boris.ostrovsky@...cle.com
Subject: Re: [PATCH v4 02/10] crash hp: Introduce CRASH_HOTPLUG configuration
 options



On 2/22/22 21:25, Baoquan He wrote:
> On 02/09/22 at 02:56pm, Eric DeVolder wrote:
>> Support for CPU and memory hotplug for crash is controlled by the
>> CRASH_HOTPLUG configuration option, introduced by this patch.
>>
>> The CRASH_HOTPLUG_ELFCOREHDR_SZ related configuration option is
>> also introduced with this patch.
>>
>> Signed-off-by: Eric DeVolder <eric.devolder@...cle.com>
>> ---
>>   arch/x86/Kconfig | 26 ++++++++++++++++++++++++++
>>   1 file changed, 26 insertions(+)
>>
>> diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
>> index ebe8fc76949a..4e3374edab02 100644
>> --- a/arch/x86/Kconfig
>> +++ b/arch/x86/Kconfig
>> @@ -2060,6 +2060,32 @@ config CRASH_DUMP
>>   	  (CONFIG_RELOCATABLE=y).
>>   	  For more details see Documentation/admin-guide/kdump/kdump.rst
>>   
>> +config CRASH_HOTPLUG
>> +	bool "kernel updates of crash elfcorehdr"
>> +	depends on CRASH_DUMP && (HOTPLUG_CPU || MEMORY_HOTPLUG) && KEXEC_FILE
>> +	help
>> +	  Enable the kernel to update the crash elfcorehdr (which contains
>> +	  the list of CPUs and memory regions) directly when hot plug/unplug
>> +	  of CPUs or memory. Otherwise userspace must monitor these hot
>> +	  plug/unplug change notifications via udev in order to
>> +	  unload-then-reload the crash kernel so that the list of CPUs and
>> +	  memory regions is kept up-to-date. Note that the udev CPU and
>> +	  memory change notifications still occur (however, userspace is not
>> +	  required to monitor for crash dump purposes).
>> +
>> +config CRASH_HOTPLUG_ELFCOREHDR_SZ
>> +	depends on CRASH_HOTPLUG
>> +	int
>> +	default 131072
>> +	help
>> +	  Specify the maximum size of the elfcorehdr buffer/segment.
>> +	  The 128KiB default is sized so that it can accommodate 2048
>> +	  Elf64_Phdr, where each Phdr represents either a CPU or a
>> +	  region of memory.
>> +	  For example, this size can accommodate hotplugging a machine
>> +	  with up to 1024 CPUs and up to 1024 memory regions (e.g. 1TiB
>> +	  with 1024 1GiB memory DIMMs).
> 
> This example of memory could be a little misleading. The memory regions
> may not be related to memory DIMMs. System could split them into many
> smaller regions during bootup.

I changed "with 1024 1GiB memory DIMMs" to "with 1024 1GiB hotplug memories".
eric

> 
> Otherwise, this patch looks good to me.
> 
>> +
>>   config KEXEC_JUMP
>>   	bool "kexec jump"
>>   	depends on KEXEC && HIBERNATION
>> -- 
>> 2.27.0
>>
>