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[217.140.101.70]) by mx.google.com with ESMTP id h10si1719490edv.8.2019.04.04.06.11.30 for ; Thu, 04 Apr 2019 06:11:30 -0700 (PDT) Received-SPF: pass (google.com: domain of anshuman.khandual@arm.com designates 217.140.101.70 as permitted sender) client-ip=217.140.101.70; Authentication-Results: mx.google.com; spf=pass (google.com: domain of anshuman.khandual@arm.com designates 217.140.101.70 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.72.51.249]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 38A17A78; Thu, 4 Apr 2019 06:11:29 -0700 (PDT) Received: from [10.162.40.100] (p8cg001049571a15.blr.arm.com [10.162.40.100]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id CA5593F68F; Thu, 4 Apr 2019 06:11:23 -0700 (PDT) Subject: Re: [PATCH 0/6] arm64/mm: Enable memory hot remove and ZONE_DEVICE To: Dan Williams Cc: Linux Kernel Mailing List , linux-arm-kernel@lists.infradead.org, Linux MM , Andrew Morton , Will Deacon , Catalin Marinas , Michal Hocko , Mel Gorman , james.morse@arm.com, Mark Rutland , Robin Murphy , cpandya@codeaurora.org, arunks@codeaurora.org, osalvador@suse.de, Logan Gunthorpe , Pavel Tatashin , David Hildenbrand , cai@lca.pw References: <1554265806-11501-1-git-send-email-anshuman.khandual@arm.com> From: Anshuman Khandual Message-ID: <6d46fc37-91e2-c44c-6e01-bfbd5c022f39@arm.com> Date: Thu, 4 Apr 2019 18:41:25 +0530 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit 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 04/03/2019 11:38 PM, Dan Williams wrote: > On Tue, Apr 2, 2019 at 9:30 PM Anshuman Khandual > wrote: >> >> This series enables memory hot remove on arm64, fixes a memblock removal >> ordering problem in generic __remove_memory(), enables sysfs memory probe >> interface on arm64. It also enables ZONE_DEVICE with struct vmem_altmap >> support. >> >> Testing: >> >> Tested hot remove on arm64 for all 4K, 16K, 64K page config options with >> all possible VA_BITS and PGTABLE_LEVELS combinations. Tested ZONE_DEVICE >> with ARM64_4K_PAGES through a dummy driver. >> >> Build tested on non arm64 platforms. I will appreciate if folks can test >> arch_remove_memory() re-ordering in __remove_memory() on other platforms. >> >> Dependency: >> >> V5 series in the thread (https://lkml.org/lkml/2019/2/14/1096) will make >> kernel linear mapping loose pgtable_page_ctor() init. When this happens >> the proposed functions free_pte|pmd|pud_table() in [PATCH 2/6] will have >> to stop calling pgtable_page_dtor(). > > Hi Anshuman, Hello Dan, > > I'd be interested to integrate this with the sub-section hotplug > support [1]. Otherwise the padding implementation in libnvdimm can't > be removed unless all ZONE_DEVICE capable archs also agree on the > minimum arch_add_memory() granularity. I'd prefer not to special case > which archs support which granularity, but it unfortunately > complicates what you're trying to achieve. Sorry I have not been following your series on sub-section hotplug support. Hence might not have the full context here. Could you please give some more details on what exactly might be a problem. > > I think at a minimum we, mm hotplug co-travellers, need to come to a > consensus on whether sub-section support is viable for v5.2 and / or a > pre-requisite for new arch-ZONE_DEVICE implementations I would need to go through sub-section hotplug series first to understand the pre-requisite. Do we need to support sub-section hotplug first before being able to enable ZONE_DEVICE ? - Anshuman