Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754315AbcKUMjP (ORCPT ); Mon, 21 Nov 2016 07:39:15 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33820 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753528AbcKUMjO (ORCPT ); Mon, 21 Nov 2016 07:39:14 -0500 Date: Mon, 21 Nov 2016 07:39:10 -0500 From: Jerome Glisse To: Anshuman Khandual Cc: akpm@linux-foundation.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, John Hubbard , Dan Williams , Ross Zwisler Subject: Re: [HMM v13 05/18] mm/ZONE_DEVICE/devmem_pages_remove: allow early removal of device memory Message-ID: <20161121123910.GE2392@redhat.com> References: <1479493107-982-1-git-send-email-jglisse@redhat.com> <1479493107-982-6-git-send-email-jglisse@redhat.com> <5832CE7A.3060802@linux.vnet.ibm.com> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <5832CE7A.3060802@linux.vnet.ibm.com> User-Agent: Mutt/1.7.1 (2016-10-04) X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.27]); Mon, 21 Nov 2016 12:39:13 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 745 Lines: 19 On Mon, Nov 21, 2016 at 04:07:46PM +0530, Anshuman Khandual wrote: > On 11/18/2016 11:48 PM, J?r?me Glisse wrote: > > HMM wants to remove device memory early before device tear down so add an > > helper to do that. > > Could you please explain why HMM wants to remove device memory before > device tear down ? > Some device driver want to manage memory for several physical devices from a single fake device driver. Because it fits their driver architecture better and those physical devices can have dedicated link between them. Issue is that the fake device driver can outlive any of the real device for a long time so we want to be able to remove device memory before the fake device goes away to free up resources early. Cheers, J?r?me