From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 0E5FCC10F0B for ; Wed, 3 Apr 2019 08:17:32 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CCAB22147A for ; Wed, 3 Apr 2019 08:17:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728978AbfDCIRa (ORCPT ); Wed, 3 Apr 2019 04:17:30 -0400 Received: from mx1.redhat.com ([209.132.183.28]:48718 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728672AbfDCIR3 (ORCPT ); Wed, 3 Apr 2019 04:17:29 -0400 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5B3DA30B9318; Wed, 3 Apr 2019 08:17:29 +0000 (UTC) Received: from [10.36.117.246] (ovpn-117-246.ams2.redhat.com [10.36.117.246]) by smtp.corp.redhat.com (Postfix) with ESMTP id A5D5C608D4; Wed, 3 Apr 2019 08:17:27 +0000 (UTC) Subject: Re: [PATCH 0/4] mm,memory_hotplug: allocate memmap from hotadded memory To: Michal Hocko , Oscar Salvador Cc: akpm@linux-foundation.org, dan.j.williams@intel.com, Jonathan.Cameron@huawei.com, anshuman.khandual@arm.com, linux-kernel@vger.kernel.org, linux-mm@kvack.org References: <20190328134320.13232-1-osalvador@suse.de> <20190329084547.5k37xjwvkgffwajo@d104.suse.de> <20190329134243.GA30026@dhcp22.suse.cz> <20190401075936.bjt2qsrhw77rib77@d104.suse.de> <20190401115306.GF28293@dhcp22.suse.cz> <20190402082812.fefamf7qlzulb7t2@d104.suse.de> <20190402124845.GD28293@dhcp22.suse.cz> <20190403080113.adj2m3szhhnvzu56@d104.suse.de> <20190403081232.GB15605@dhcp22.suse.cz> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190403081232.GB15605@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.49]); Wed, 03 Apr 2019 08:17:29 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 03.04.19 10:12, Michal Hocko wrote: > On Wed 03-04-19 10:01:16, Oscar Salvador wrote: >> On Tue, Apr 02, 2019 at 02:48:45PM +0200, Michal Hocko wrote: >>> So what is going to happen when you hotadd two memblocks. The first one >>> holds memmaps and then you want to hotremove (not just offline) it? >> >> If you hot-add two memblocks, this means that either: >> >> a) you hot-add a 256MB-memory-device (128MB per memblock) >> b) you hot-add two 128MB-memory-device >> >> Either way, hot-removing only works for memory-device as a whole, so >> there is no problem. >> >> Vmemmaps are created per hot-added operations, this means that >> vmemmaps will be created for the hot-added range. >> And since hot-add/hot-remove operations works with the same granularity, >> there is no problem. > > What does prevent calling somebody arch_add_memory for a range spanning > multiple memblocks from a driver directly. In other words aren't you To drivers, we only expose add_memory() and friends. And I think this is a good idea. > making assumptions about a future usage based on the qemu usecase? > As I noted, we only have an issue if add add_memory() and remove_memory() is called with different granularity. I gave two examples where this might not be the case, but we will have to look int the details. -- Thanks, David / dhildenb