From mboxrd@z Thu Jan  1 00:00:00 1970
From: Alistair Popple <apopple@nvidia.com>
Date: Wed, 17 Feb 2021 23:00:54 +0000
Subject: Re: [PATCH 0/9] Add support for SVM atomics in Nouveau
Message-Id: <6616185.Wbe1NtApLk@nvdebian>
List-Id: <kvm-ppc.vger.kernel.org>
References: <20210209010722.13839-1-apopple@nvidia.com> <20210210175913.GO4718@ziepe.ca> <20210211075510.GA2368090@infradead.org>
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To: linux-mm@kvack.org
Cc: Christoph Hellwig <hch@infradead.org>, Jason Gunthorpe <jgg@ziepe.ca>, John Hubbard <jhubbard@nvidia.com>, Daniel Vetter <daniel@ffwll.ch>, Nouveau Dev <nouveau@lists.freedesktop.org>, Ben Skeggs <bskeggs@redhat.com>, Andrew Morton <akpm@linux-foundation.org>, Linux Doc Mailing List <linux-doc@vger.kernel.org>, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, kvm-ppc@vger.kernel.org, dri-devel <dri-devel@lists.freedesktop.org>, Ralph Campbell <rcampbell@nvidia.com>, Jerome Glisse <jglisse@redhat.com>

On Thursday, 11 February 2021 6:55:10 PM AEDT Christoph Hellwig wrote:
> On Wed, Feb 10, 2021 at 01:59:13PM -0400, Jason Gunthorpe wrote:
> > Really what you want to do here is leave the CPU page in the VMA and
> > the page tables where it started and deny CPU access to the page. Then
> > all the proper machinery will continue to work.
> > 
> > IMHO "migration" is the wrong idea if the data isn't actually moving.
> 
> Agreed.
 
I chose "migration" because device private pages seemed like a good way of 
reusing existing code to do what was required (a callback on CPU access).

However I have been reworking this to use mmu notifiers as the callback and it 
seems to simplify some things nicely so think I also agree. It removes the 
requirement for the pin as well which is nice, I'll post it as a v2 soon.

 - Alistair