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Message-ID: <e0f5adf6-4f47-75c7-5697-5e928bee14b7@oracle.com>
Date: Thu, 29 Jun 2023 17:31:33 -0500
From: Eric DeVolder <eric.devolder@...cle.com>
To: Randy Dunlap <rdunlap@...radead.org>, linux-kernel@...r.kernel.org,
david@...hat.com, osalvador@...e.de, corbet@....net,
tglx@...utronix.de, mingo@...hat.com, bp@...en8.de,
dave.hansen@...ux.intel.com, x86@...nel.org, bhe@...hat.com,
ebiederm@...ssion.com, kexec@...ts.infradead.org
Cc: hpa@...or.com, gregkh@...uxfoundation.org, rafael@...nel.org,
vgoyal@...hat.com, dyoung@...hat.com, lf32.dev@...il.com,
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boris.ostrovsky@...cle.com
Subject: Re: [PATCH v25 06/10] crash: memory and CPU hotplug sysfs attributes
Randy,
Thanks for looking at this! Inline comments below.
eric
On 6/29/23 15:59, Randy Dunlap wrote:
> Hi--
>
> On 6/29/23 12:21, Eric DeVolder wrote:
>>
>> Signed-off-by: Eric DeVolder <eric.devolder@...cle.com>
>> Reviewed-by: Sourabh Jain <sourabhjain@...ux.ibm.com>
>> Acked-by: Hari Bathini <hbathini@...ux.ibm.com>
>> Acked-by: Baoquan He <bhe@...hat.com>
>> ---
>> Documentation/ABI/testing/sysfs-devices-memory | 8 ++++++++
>> .../ABI/testing/sysfs-devices-system-cpu | 8 ++++++++
>> .../admin-guide/mm/memory-hotplug.rst | 8 ++++++++
>> Documentation/core-api/cpu_hotplug.rst | 18 ++++++++++++++++++
>> drivers/base/cpu.c | 16 ++++++++++++++--
>> drivers/base/memory.c | 13 +++++++++++++
>> include/linux/kexec.h | 8 ++++++++
>> 7 files changed, 77 insertions(+), 2 deletions(-)
>>
>
>> diff --git a/Documentation/admin-guide/mm/memory-hotplug.rst b/Documentation/admin-guide/mm/memory-hotplug.rst
>> index 1b02fe5807cc..eb99d79223a3 100644
>> --- a/Documentation/admin-guide/mm/memory-hotplug.rst
>> +++ b/Documentation/admin-guide/mm/memory-hotplug.rst
>> @@ -291,6 +291,14 @@ The following files are currently defined:
>> Availability depends on the CONFIG_ARCH_MEMORY_PROBE
>> kernel configuration option.
>> ``uevent`` read-write: generic udev file for device subsystems.
>> +``crash_hotplug`` read-only: when changes to the system memory map
>> + occur due to hot un/plug of memory, this file contains
>> + '1' if the kernel updates the kdump capture kernel memory
>> + map itself (via elfcorehdr), or '0' if userspace must update
>> + the kdump capture kernel memory map.
>> +
>> + Availability depends on the CONFIG_MEMORY_HOTPLUG kernel
>> + configuration option.
>> ====================== =========================================================
>
> Did you test build the documentation?
> It looks to me like the end-of-table '=' signs line needs 3 more === to be long
> enough for the text above it.
Hmm, the 'make htmldocs' renders and views ok. Is there perhaps another method I should use?
>
>>
>> .. note::
>> diff --git a/Documentation/core-api/cpu_hotplug.rst b/Documentation/core-api/cpu_hotplug.rst
>> index e6f5bc39cf5c..54581c501562 100644
>> --- a/Documentation/core-api/cpu_hotplug.rst
>> +++ b/Documentation/core-api/cpu_hotplug.rst
>> @@ -741,6 +741,24 @@ will receive all events. A script like::
>>
>> can process the event further.
>>
>> +When changes to the CPUs in the system occur, the sysfs file
>> +/sys/devices/system/cpu/crash_hotplug contains '1' if the kernel
>> +updates the kdump capture kernel list of CPUs itself (via elfcorehdr),
>> +or '0' if userspace must update the kdump capture kernel list of CPUs.
>> +
>> +The availability depends on the CONFIG_HOTPLUG_CPU kernel configuration
>> +option.
>> +
>> +To skip userspace processing of CPU hot un/plug events for kdump
>> +(ie the unload-then-reload to obtain a current list of CPUs), this sysfs
>
> i.e.
>
got it, thanks.
>> +file can be used in a udev rule as follows:
>> +
>> + SUBSYSTEM=="cpu", ATTRS{crash_hotplug}=="1", GOTO="kdump_reload_end"
>> +
>> +For a cpu hot un/plug event, if the architecture supports kernel updates
>
> CPU
> for consistency
>
got it, thanks.
>> +of the elfcorehdr (which contains the list of CPUs), then the rule skips
>> +the unload-then-reload of the kdump capture kernel.
>> +
>> Kernel Inline Documentations Reference
>> ======================================
>>
>
> Thanks.
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