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[209.85.220.65]) by mx.google.com with SMTPS id d13sor8744449oih.174.2019.04.03.11.09.05 for (Google Transport Security); Wed, 03 Apr 2019 11:09:05 -0700 (PDT) Received-SPF: pass (google.com: domain of dan.j.williams@intel.com designates 209.85.220.65 as permitted sender) client-ip=209.85.220.65; Authentication-Results: mx.google.com; dkim=pass header.i=@intel-com.20150623.gappssmtp.com header.s=20150623 header.b=z8K+qZbK; spf=pass (google.com: domain of dan.j.williams@intel.com designates 209.85.220.65 as permitted sender) smtp.mailfrom=dan.j.williams@intel.com; dmarc=pass (p=NONE sp=NONE dis=NONE) header.from=intel.com DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=intel-com.20150623.gappssmtp.com; s=20150623; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=WLfeTHYa0RD16P6+TGw1835NRm1Z2mjwVm5mp+9PwC4=; b=z8K+qZbKKB0CPbds0ctgzT6yvbDSyne4jzF+g9MQDqHCPB5OPh0qk2XXWxoiT8uT9G zzAZBBgiwvP3s3WO+yER7TdXgooNtVJn+bJrYtKWk0AUmM4gMN9g2NYXSa+GjS+RD4qh 8xENTTZm8SgBjQ9esMCmbOP5N89LgbdkK2DEsHPY7bvoNzu4jgR80ZG3HLSzPxh0WrY5 S0JNoxdJG64cPYngeWk+znmXW9+iCzcbLOjAVOekrPZVxNPgEekx0LW/gdB8hbrAEi1G xsvjGauCjnbGtT2gFDUKoUQw5H1XawOs5hYrgAV4dxTSwt6qZz7tP5wZXt4VslUi4kvi mGuA== X-Google-Smtp-Source: APXvYqzusb0p4qiWWjm2CpnwMPhzr5akGYhKWUDDAJTvVOvkzYZTem1qs/kZxvPv4FWYtmfE1KTFPIoKblD2l9anuTo= X-Received: by 2002:aca:f581:: with SMTP id t123mr589000oih.0.1554314944750; Wed, 03 Apr 2019 11:09:04 -0700 (PDT) MIME-Version: 1.0 References: <1554265806-11501-1-git-send-email-anshuman.khandual@arm.com> In-Reply-To: <1554265806-11501-1-git-send-email-anshuman.khandual@arm.com> From: Dan Williams Date: Wed, 3 Apr 2019 11:08:53 -0700 Message-ID: Subject: Re: [PATCH 0/6] arm64/mm: Enable memory hot remove and ZONE_DEVICE To: Anshuman Khandual 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 Content-Type: text/plain; charset="UTF-8" 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 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, 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. 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.