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[209.132.183.28]) by mx.google.com with ESMTPS id f51si516171qte.155.2019.04.03.01.36.08 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Wed, 03 Apr 2019 01:36:08 -0700 (PDT) Received-SPF: pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) client-ip=209.132.183.28; Authentication-Results: mx.google.com; spf=pass (google.com: domain of david@redhat.com designates 209.132.183.28 as permitted sender) smtp.mailfrom=david@redhat.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=redhat.com Received: from smtp.corp.redhat.com (int-mx02.intmail.prod.int.phx2.redhat.com [10.5.11.12]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5D46981F10; Wed, 3 Apr 2019 08:36:07 +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 A0C1C60240; Wed, 3 Apr 2019 08:36:05 +0000 (UTC) Subject: Re: [PATCH 0/4] mm,memory_hotplug: allocate memmap from hotadded memory To: Oscar Salvador , Michal Hocko 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: <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> <20190403083359.vqbzy5krjfzfjedx@d104.suse.de> From: David Hildenbrand Openpgp: preference=signencrypt Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.4.0 MIME-Version: 1.0 In-Reply-To: <20190403083359.vqbzy5krjfzfjedx@d104.suse.de> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.79 on 10.5.11.12 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.25]); Wed, 03 Apr 2019 08:36:07 +0000 (UTC) X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On 03.04.19 10:34, Oscar Salvador wrote: > On Wed, Apr 03, 2019 at 10:12:32AM +0200, Michal Hocko wrote: >> What does prevent calling somebody arch_add_memory for a range spanning >> multiple memblocks from a driver directly. In other words aren't you >> making assumptions about a future usage based on the qemu usecase? > > Well, right now they cannot as it is not exported. > But if we want to do it in the future, then yes, I would have to > be more careful because I made the assumption that hot-add/hot-remove > are working with the same granularity, which is the case right now. > > Given said this, I think that something like you said before, giving > the option to the caller to specify whether it wants vmemmaps per the > whole hot-added range or per memblock is a reasonable thing to do. > That way, there will not be a problem working with different granularities > in hot-add/hot-remove operations and we would be on safe side. There might still be an issue if the person adding memory might be somebody else removing memory. I am not yet sure if we should even allow add_memory/remove_memory with different granularity. But as I noted, ACPI and powernv. -- Thanks, David / dhildenb