From mboxrd@z Thu Jan  1 00:00:00 1970
From: Jason Gunthorpe <jgg@ziepe.ca>
Date: Mon, 16 Mar 2020 18:17:07 +0000
Subject: Re: [PATCH 1/2] mm: handle multiple owners of device private pages in migrate_vma
Message-Id: <20200316181707.GJ20941@ziepe.ca>
List-Id: <kvm-ppc.vger.kernel.org>
References: <20200316175259.908713-1-hch@lst.de>
 <20200316175259.908713-2-hch@lst.de>
In-Reply-To: <20200316175259.908713-2-hch@lst.de>
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To: Christoph Hellwig <hch@lst.de>
Cc: Dan Williams <dan.j.williams@intel.com>, Bharata B Rao <bharata@linux.ibm.com>, Christian =?utf-8?B?S8O2bmln?= <christian.koenig@amd.com>, Ben Skeggs <bskeggs@redhat.com>, Jerome Glisse <jglisse@redhat.com>, kvm-ppc@vger.kernel.org, amd-gfx@lists.freedesktop.org, dri-devel@lists.freedesktop.org, nouveau@lists.freedesktop.org, linux-mm@kvack.org

On Mon, Mar 16, 2020 at 06:52:58PM +0100, Christoph Hellwig wrote:
> Add a new opaque owner field to struct dev_pagemap, which will allow
> the hmm and migrate_vma code to identify who owns ZONE_DEVICE memory,
> and refuse to work on mappings not owned by the calling entity.

Using a pointer seems like a good solution to me.

Is this a bug fix? What is the downside for migrate on pages it
doesn't work? I'm not up to speed on migrate..

Jason