[PATCH v12 7/7] x86/crash: Add x86 crash hotplug support
Borislav Petkov
bp at alien8.de
Tue Oct 25 03:31:59 PDT 2022
On Thu, Oct 13, 2022 at 10:57:28AM +0800, Baoquan He wrote:
> The concern to range number mainly is on Virt guest systems.
And why would virt emulate 1K hotpluggable DIMM slots and not emulate a
real machine?
> On baremetal system, basically only very high end server support
> memory hotplug. I ever visited customer's lab and saw one server,
> it owns 8 slots, on each slot a box containing about 20 cpus and 2T
> memory at most can be plugged in at one time. So people won't make too
> many slots for hotplugging since it's too expensive.
There you have it - the persuading argument.
> I checked user space kexec code, the maximum memory range number is
> honored to x86_64 because of a HPE SGI system. After that, nobody
> complains about it. Please see below user space kexec-tools commit in
> https://git.kernel.org/pub/scm/utils/kernel/kexec/kexec-tools.git
>
> The memory ranges may be not all made by different DIMM slots, could be
> firmware reservatoin, e.g efi/BIOS diggged out physical memory,
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
I don't know what that means.
If it is firmware crap, you want to exclude that from kdump anyway.
> Now CONFIG_NR_CPUS has the maximum number as 8192. And user space
> kexec-tools has maximum memory range number as 2048. We can take
> the current 8192 + 2048 = 10K as default value conservatively. Or
> take 8192 + 2048 * 2 = 12K which has two times of maximum memory range
> bumber in kexec-tools. What do you think?
I still think that we should stick to reality and support what is
possible not what is potentially and theoretically there.
Thx.
--
Regards/Gruss,
Boris.
https://people.kernel.org/tglx/notes-about-netiquette
More information about the kexec
mailing list