From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <owner-linux-mm@kvack.org>
Received: from mail-pf1-f197.google.com (mail-pf1-f197.google.com [209.85.210.197])
	by kanga.kvack.org (Postfix) with ESMTP id 6DC318E00E5
	for <linux-mm@kvack.org>; Wed, 12 Dec 2018 17:12:05 -0500 (EST)
Received: by mail-pf1-f197.google.com with SMTP id s14so16423880pfk.16
        for <linux-mm@kvack.org>; Wed, 12 Dec 2018 14:12:05 -0800 (PST)
Received: from bombadil.infradead.org (bombadil.infradead.org. [2607:7c80:54:e::133])
        by mx.google.com with ESMTPS id p4si15219772pga.514.2018.12.12.14.12.04
        for <linux-mm@kvack.org>
        (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256);
        Wed, 12 Dec 2018 14:12:04 -0800 (PST)
Date: Wed, 12 Dec 2018 14:11:57 -0800
From: Matthew Wilcox <willy@infradead.org>
Subject: Re: [PATCH 1/2] mm: introduce put_user_page*(), placeholder versions
Message-ID: <20181212221157.GL6830@bombadil.infradead.org>
References: <7b4733be-13d3-c790-ff1b-ac51b505e9a6@nvidia.com>
 <20181207191620.GD3293@redhat.com>
 <3c4d46c0-aced-f96f-1bf3-725d02f11b60@nvidia.com>
 <20181208022445.GA7024@redhat.com>
 <20181210102846.GC29289@quack2.suse.cz>
 <20181212150319.GA3432@redhat.com>
 <CAPcyv4go0Xzhz8rXdfscWuXDu83BO9v8WD4upDUJWb7gKzX5OQ@mail.gmail.com>
 <20181212213005.GE5037@redhat.com>
 <CAPcyv4gJHeFjEgna1S-2uE4KxkSUgkc=e=2E5oqfoirec84C-w@mail.gmail.com>
 <20181212215348.GF5037@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20181212215348.GF5037@redhat.com>
Sender: owner-linux-mm@kvack.org
List-ID: <linux-mm.kvack.org>
To: Jerome Glisse <jglisse@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>, Jan Kara <jack@suse.cz>, John Hubbard <jhubbard@nvidia.com>, John Hubbard <john.hubbard@gmail.com>, Andrew Morton <akpm@linux-foundation.org>, Linux MM <linux-mm@kvack.org>, tom@talpey.com, Al Viro <viro@zeniv.linux.org.uk>, benve@cisco.com, Christoph Hellwig <hch@infradead.org>, Christopher Lameter <cl@linux.com>, "Dalessandro, Dennis" <dennis.dalessandro@intel.com>, Doug Ledford <dledford@redhat.com>, Jason Gunthorpe <jgg@ziepe.ca>, Michal Hocko <mhocko@kernel.org>, Mike Marciniszyn <mike.marciniszyn@intel.com>, rcampbell@nvidia.com, Linux Kernel Mailing List <linux-kernel@vger.kernel.org>, linux-fsdevel <linux-fsdevel@vger.kernel.org>, "Weiny, Ira" <ira.weiny@intel.com>

On Wed, Dec 12, 2018 at 04:53:49PM -0500, Jerome Glisse wrote:
> The mmu notifier i put forward is the emergency revoke ie last
> resort after driver have done everything it could to inform user-
> space and release the pages. So doing thing brutaly in it like
> reprogramming driver page table (which AFAIK is something you
> can do on any hardware wether the hardware will like it or not
> is a different question).

You can't do it to an NVMe device.  You submit the DMA addresses in
the command, and the device reads the command at submission time.
There's no way to change the DMA addresses for an in-flight command.