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

[Eric DeVolder]

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.