Re: [PATCH v25 06/10] crash: memory and CPU hotplug sysfs attributes

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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@xxxxxxxxxx>
Reviewed-by: Sourabh Jain <sourabhjain@xxxxxxxxxxxxx>
Acked-by: Hari Bathini <hbathini@xxxxxxxxxxxxx>
Acked-by: Baoquan He <bhe@xxxxxxxxxx>
---
  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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