On Thu, Sep 10, 2020 at 02:48:47PM +0200, Michal Hocko wrote:
> > Is there any actual usecase for a configuration like this? What is the
> > point to statically define additional memory like this when the same can
> > be achieved on the same command line?
Well, for qemu I am not sure, but if David is right, it seems you can face
the same if you reboot a vm with hotplugged memory.
Moreover, it seems that the problem we spotted with [1], it was a VM running on
Promox (KVM).
The Hypervisor probably said at boot time "Ey, I do have these ACPI devices, care
to enable them now"?
As always, there are all sorts of configurations/scenarios out there in the wild.
> Forgot to ask one more thing. Who is going to online that memory when
> userspace is not running yet?
Depends, if you have CONFIG_MEMORY_HOTPLUG_DEFAULT_ONLINE set or you specify
memhp_default_online_type=[online,online_*], memory will get onlined right
after hot-adding stage:
/* online pages if requested */
if (memhp_default_online_type != MMOP_OFFLINE)
walk_memory_blocks(start, size, NULL, online_memory_block);
If not, systemd-udev will do the magic once the system is up.
--
Oscar Salvador
SUSE L3
