Re: [PATCH v5 2/8] x86/crash hp: Introduce CRASH_HOTPLUG configuration options

[Eric DeVolder]

On 3/21/22 06:59, Baoquan He wrote:
> On 03/03/22 at 11:27am, 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.
>
> Maybe can rephrase it as:
>
> x86/crash: Introduce new options to support cpu and memory hotplug of crash
>   
> CRASH_HOTPLUG is to enable cpu and memory hotplug of crash.
>
> CRASH_HOTPLUG_ELFCOREHDR_SZ is used to Specify the maximum size of
> the elfcorehdr buffer/segment.
>   
> This is a preparation for later usage.
>
> Otherwise, this looks good to me.
Commit message updated.
eric

> > Signed-off-by: Eric DeVolder <eric.devolder@xxxxxxxxxx>
> > ---
> >   arch/x86/Kconfig | 26 ++++++++++++++++++++++++++
> >   1 file changed, 26 insertions(+)
> >
> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index 9f5bd41bf660..37eb26563f07 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -2061,6 +2061,32 @@ 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 a machine with up to 1024
> > +	  CPUs and up to 1024 memory regions, eg. as represented by the
> > +	  'System RAM' entries in /proc/iomem.
> > +
> >   config KEXEC_JUMP
> >   	bool "kexec jump"
> >   	depends on KEXEC && HIBERNATION
> > --
> > 2.27.0