linux-kernel - Re: [PATCH 5/5] memremap: provide a not device managed memremap

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Message-ID: <20190812150012.GA12700@lst.de>
Date:   Mon, 12 Aug 2019 17:00:12 +0200
From:   Christoph Hellwig <hch@....de>
To:     Bharata B Rao <bharata@...ux.ibm.com>
Cc:     Christoph Hellwig <hch@....de>,
        Dan Williams <dan.j.williams@...el.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-nvdimm@...ts.01.org
Subject: Re: [PATCH 5/5] memremap: provide a not device managed
 memremap_pages

On Mon, Aug 12, 2019 at 08:20:58PM +0530, Bharata B Rao wrote:
> On Sun, Aug 11, 2019 at 10:12:47AM +0200, Christoph Hellwig wrote:
> > The kvmppc ultravisor code wants a device private memory pool that is
> > system wide and not attached to a device.  Instead of faking up one
> > provide a low-level memremap_pages for it.  Note that this function is
> > not exported, and doesn't have a cleanup routine associated with it to
> > discourage use from more driver like users.
> 
> The kvmppc secure pages management code will be part of kvm-hv which
> can be built as module too. So it would require memremap_pages() to be
> exported.
> 
> Additionally, non-dev version of the cleanup routine
> devm_memremap_pages_release() or equivalent would also be requried.
> With device being present, put_device() used to take care of this
> cleanup.

Oh well.  We can add them fairly easily if we really need to, but I
tried to avoid that.  Can you try to see if this works non-modular
for you for now until we hear more feedback from Dan?