linux-kernel - Re: [PATCH 09/15] mm/hmm/devmem: device memory hotplug using ZONE

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Message-ID: <20170801121755.GJ15774@dhcp22.suse.cz>
Date:   Tue, 1 Aug 2017 14:17:55 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Jerome Glisse <jglisse@...hat.com>
Cc:     akpm@...ux-foundation.org, linux-kernel@...r.kernel.org,
        linux-mm@...ck.org, John Hubbard <jhubbard@...dia.com>,
        Dan Williams <dan.j.williams@...el.com>,
        David Nellans <dnellans@...dia.com>,
        Evgeny Baskakov <ebaskakov@...dia.com>,
        Mark Hairgrove <mhairgrove@...dia.com>,
        Sherry Cheung <SCheung@...dia.com>,
        Subhash Gutti <sgutti@...dia.com>
Subject: Re: [PATCH 09/15] mm/hmm/devmem: device memory hotplug using
 ZONE_DEVICE v6

On Mon 31-07-17 13:21:24, Jerome Glisse wrote:
> On Fri, Jul 28, 2017 at 01:10:03PM +0200, Michal Hocko wrote:
> > I haven't seen a newer version posted but the same comment applies on
> > your hmm-v25-4.9 git version from
> > git://people.freedesktop.org/~glisse/linux
> > 
> > On Wed 28-06-17 14:00:41, Jérôme Glisse wrote:
> > > This introduce a simple struct and associated helpers for device driver
> > > to use when hotpluging un-addressable device memory as ZONE_DEVICE. It
> > > will find a unuse physical address range and trigger memory hotplug for
> > > it which allocates and initialize struct page for the device memory.
> > 
> > Please document the hotplug semantic some more please (who is in charge,
> > what is the lifetime, userspace API to add/remove this memory if any
> > etc...).
> > 
> > I can see you call add_pages. Please document why arch_add_memory (like
> > devm_memremap_pages) is not used. You also never seem to online the
> > range which is in line with nvdim usage and it is OK. But then I fail to
> > understand why you need
> 
> I added documentation in function and in commit message:
> https://cgit.freedesktop.org/~glisse/linux/commit/?h=hmm-next&id=33e236a64da84423c83db401fc62ea13877111f2

OK, that makes more clear. Thanks!
-- 
Michal Hocko
SUSE Labs