Received: by 2002:a05:6a10:8c0a:0:0:0:0 with SMTP id go10csp6835571pxb;
        Wed, 17 Feb 2021 15:05:22 -0800 (PST)
X-Google-Smtp-Source: ABdhPJyTY+i3VyvdGNJ2R47L0XJTNTa1S4O9qoWXwkL+SkkOss/Z9Cjq8SmXDzfQqJAhbPbUorwY
X-Received: by 2002:aa7:cc98:: with SMTP id p24mr1168448edt.126.1613603122492;
        Wed, 17 Feb 2021 15:05:22 -0800 (PST)
ARC-Seal: i=1; a=rsa-sha256; t=1613603122; cv=none;
        d=google.com; s=arc-20160816;
        b=fYaEBUulxlY6JWRl/y5CkVqmatZkqG5hb1ffeDIKxzFvpSRTH7TdzzzAfrLuANBnaU
         m7rifyWy3kol6Ywy9mr4tNBDBUS2Ya0rd9GddkHQ93RsQQf9GjbL91uDVbcRQghNdQ6N
         6ogzs2AqC+SwBxA8gz+ELnYXYzTEXxc1Q93XboOSbjthx3KNjgCriq7T2alKbr/YNl33
         UOfWCW4q67FFEbi/Ex8W39QFDtSwBw+dZ3RfOT6vetWb3LoJzuPqxZsgJG7suPxdu04k
         GSgOWc3P0rZun/zqLcLZ6lPXBOEtznMTfCbuiiY8YEf6K8wlUGt6mqyNdqssAJhuPiOp
         8oCg==
ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=arc-20160816;
        h=list-id:precedence:dkim-signature:content-transfer-encoding
         :mime-version:references:in-reply-to:message-id:date:subject:cc:to
         :from;
        bh=Zcp6FwQOo6uCl+bAC2DWEr4Viwiu5nIBT+YN6D2qruU=;
        b=c2eJvK0k65dVVtVHeqe2NT1BW0YX28yRVteL33W18JxWmykjRC8zOlghRjAZzEMf3V
         RZQy0/yNGjdqzPxGx5KXbmNm/WGVg4efDVWb7WKlu4t/92gDAuLPBqQ+sg8qzsOA2zwi
         La9iT3fJxrUVQIkf8NTCSy6ZRTLfjBRwqJE159YQNAA0S5hsoLRItrViFeb0w8gP5eme
         Y3W7tWVW74gqms/NL8mVmCZsOH7z1PHVxH5RWWA4P85R4wqAdJ7sPH6BUIZibocoeT3L
         1YZMyiq1F7imx8TGNMchlfsDY8o5YzNvMMoun68eNyTy1+VzPa6VoaFwQQeWV1R6W68p
         qDPg==
ARC-Authentication-Results: i=1; mx.google.com;
       dkim=pass header.i=@nvidia.com header.s=n1 header.b=AXb+ut3o;
       spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org;
       dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: from vger.kernel.org (vger.kernel.org. [23.128.96.18])
        by mx.google.com with ESMTP id q22si2250966edc.553.2021.02.17.15.04.52;
        Wed, 17 Feb 2021 15:05:22 -0800 (PST)
Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
Authentication-Results: mx.google.com;
       dkim=pass header.i=@nvidia.com header.s=n1 header.b=AXb+ut3o;
       spf=pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org;
       dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=nvidia.com
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
        id S231462AbhBQXBk (ORCPT <rfc822;lphwiki@gmail.com> + 99 others);
        Wed, 17 Feb 2021 18:01:40 -0500
Received: from hqnvemgate25.nvidia.com ([216.228.121.64]:16785 "EHLO
        hqnvemgate25.nvidia.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
        with ESMTP id S229774AbhBQXBk (ORCPT
        <rfc822;linux-kernel@vger.kernel.org>);
        Wed, 17 Feb 2021 18:01:40 -0500
Received: from hqmail.nvidia.com (Not Verified[216.228.121.13]) by hqnvemgate25.nvidia.com (using TLS: TLSv1.2, AES256-SHA)
        id <B602da02b0005>; Wed, 17 Feb 2021 15:00:59 -0800
Received: from nvdebian.localnet (172.20.145.6) by HQMAIL107.nvidia.com
 (172.20.187.13) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Wed, 17 Feb
 2021 23:00:56 +0000
From:   Alistair Popple <apopple@nvidia.com>
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>
Subject: Re: [PATCH 0/9] Add support for SVM atomics in Nouveau
Date:   Thu, 18 Feb 2021 10:00:54 +1100
Message-ID: <6616185.Wbe1NtApLk@nvdebian>
In-Reply-To: <20210211075510.GA2368090@infradead.org>
References: <20210209010722.13839-1-apopple@nvidia.com> <20210210175913.GO4718@ziepe.ca> <20210211075510.GA2368090@infradead.org>
MIME-Version: 1.0
Content-Transfer-Encoding: 7Bit
Content-Type: text/plain; charset="us-ascii"
X-Originating-IP: [172.20.145.6]
X-ClientProxiedBy: HQMAIL111.nvidia.com (172.20.187.18) To
 HQMAIL107.nvidia.com (172.20.187.13)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nvidia.com; s=n1;
        t=1613602859; bh=Zcp6FwQOo6uCl+bAC2DWEr4Viwiu5nIBT+YN6D2qruU=;
        h=From:To:CC:Subject:Date:Message-ID:In-Reply-To:References:
         MIME-Version:Content-Transfer-Encoding:Content-Type:
         X-Originating-IP:X-ClientProxiedBy;
        b=AXb+ut3ot7Odaa4NfndUdnHlBWh/CmCbxa90e7XGqYDqOl0itTA0ey/0xdqSoXbA2
         JlMNydOcVXGiAO1uyIryQXCh6IJNMB5+ajbf7PvbtDcER0T/TTnEqkgpU2USIY0Ya+
         NqYaHlrJc7yam1VcZFkBNUvumzVGyvnQedJAd2+hs20Ac8NKfjzT6p3t31zwxNt/Hq
         gR+sHNOCuxdnohI6TOW7pnPo+iGVNWMyVlv0cNOIZszQSsdsXR69vsDcRIyKwiHLuU
         QHMPy9U3pXXKcoKf2xltHJbe92pWiS2sWG6fQJuE1wnVVzjgSmr5R0ufLguVI0LbOK
         oydiyGx+ixcIg==
Precedence: bulk
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

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