linux-kernel - Re: [PATCH 3/8] mm/memory_hotplug: add APIs for explicit online type control

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Message-ID: <aXLCAtwMkSMH3DNj@gourry-fedora-PF4VCD3F>
Date: Thu, 22 Jan 2026 19:34:10 -0500
From: Gregory Price <gourry@...rry.net>
To: "David Hildenbrand (Red Hat)" <david@...nel.org>
Cc: linux-mm@...ck.org, linux-cxl@...r.kernel.org, nvdimm@...ts.linux.dev,
	linux-kernel@...r.kernel.org, virtualization@...ts.linux.dev,
	kernel-team@...a.com, dan.j.williams@...el.com,
	vishal.l.verma@...el.com, dave.jiang@...el.com, mst@...hat.com,
	jasowang@...hat.com, xuanzhuo@...ux.alibaba.com,
	eperezma@...hat.com, osalvador@...e.de, akpm@...ux-foundation.org
Subject: Re: [PATCH 3/8] mm/memory_hotplug: add APIs for explicit online type
 control

On Thu, Jan 22, 2026 at 11:41:24PM +0100, David Hildenbrand (Red Hat) wrote:
> 
> Right, but I don't want any other OOT kernel module to be able to make use
> of add_memory_driver_managed() to do arbitrary things, because we don't know
> if it's really user space setting the policy for that memory then.
> 

Ah, this was lost on me.

> So either restrict add_memory_driver_managed() to kmem+virtio_mem
> completely, or add another variant that will be kmem-only (or however that
> dax/cxl module is called).

unclear to me how to restrict a function to specific drivers, but i can
add add_and_online_memory_driver_managed() trivially so no big issue.

You'd be ok with with this?

add_and_online_memory_driver_managed(..., online_type) {
   ... existing add_memory_driver_managed() code ...
}

add_memory_driver_managed(...) {
   add_and_online_memory_driver_managed(..., mhp_get_default_policy());
}

~Gregory