From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mx1.redhat.com ([209.132.183.28]:58526 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729695AbfGOKvc (ORCPT ); Mon, 15 Jul 2019 06:51:32 -0400 Subject: Re: [PATCH v3 02/11] s390x/mm: Fail when an altmap is used for arch_add_memory() References: <20190527111152.16324-1-david@redhat.com> <20190527111152.16324-3-david@redhat.com> <20190701074306.GC6376@dhcp22.suse.cz> <20190701124628.GT6376@dhcp22.suse.cz> From: David Hildenbrand Message-ID: <86f3ff3d-d035-a806-88b7-b8c7b77c206e@redhat.com> Date: Mon, 15 Jul 2019 12:51:27 +0200 MIME-Version: 1.0 In-Reply-To: <20190701124628.GT6376@dhcp22.suse.cz> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Sender: linux-s390-owner@vger.kernel.org List-ID: To: Michal Hocko Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-ia64@vger.kernel.org, linuxppc-dev@lists.ozlabs.org, linux-s390@vger.kernel.org, linux-sh@vger.kernel.org, linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, Dan Williams , Wei Yang , Igor Mammedov , Martin Schwidefsky , Heiko Carstens , Mike Rapoport , Vasily Gorbik , Oscar Salvador On 01.07.19 14:46, Michal Hocko wrote: > On Mon 01-07-19 09:43:06, Michal Hocko wrote: >> On Mon 27-05-19 13:11:43, David Hildenbrand wrote: >>> ZONE_DEVICE is not yet supported, fail if an altmap is passed, so we >>> don't forget arch_add_memory()/arch_remove_memory() when unlocking >>> support. >> >> Why do we need this? Sure ZONE_DEVICE is not supported for s390 and so >> might be the case for other arches which support hotplug. I do not see >> much point in adding warning to each of them. > > I would drop this one. If there is a strong reason to have something > like that it should come with a better explanation and it can be done on > top. > This was requested by Dan and I agree it is the right thing to do. In the context of paravirtualized devices (e.g., virtio-pmem), it makes sense to block functionality an arch does not support. I'll leave the decision to Andrew. -- Thanks, David / dhildenb