Re: [PATCH v6 2/8] x86/crash: Introduce new options to support cpu and memory hotplug

[Eric DeVolder]

On 4/8/22 03:07, Baoquan He wrote:
> On 04/01/22 at 02:30pm, Eric DeVolder wrote:
> > CRASH_HOTPLUG is to enable cpu and memory hotplug support 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.
> >
> > Signed-off-by: Eric DeVolder <eric.devolder@xxxxxxxxxx>
>
> LGTM,
>
> Acked-by: Baoquan He <bhe@xxxxxxxxxx>

Excellent, thanks!
eric

> > ---
> >   arch/x86/Kconfig | 26 ++++++++++++++++++++++++++
> >   1 file changed, 26 insertions(+)
> >
> > diff --git a/arch/x86/Kconfig b/arch/x86/Kconfig
> > index 7340d9f01b62..8b51d3196b82 100644
> > --- a/arch/x86/Kconfig
> > +++ b/arch/x86/Kconfig
> > @@ -2072,6 +2072,32 @@ 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