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[217.140.110.172]) by mx.google.com with ESMTP id d16si1746747ejp.292.2019.06.21.05.53.05 for ; Fri, 21 Jun 2019 05:53:05 -0700 (PDT) Received-SPF: pass (google.com: domain of anshuman.khandual@arm.com designates 217.140.110.172 as permitted sender) client-ip=217.140.110.172; Authentication-Results: mx.google.com; spf=pass (google.com: domain of anshuman.khandual@arm.com designates 217.140.110.172 as permitted sender) smtp.mailfrom=anshuman.khandual@arm.com Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id 0978E142F; Fri, 21 Jun 2019 05:53:05 -0700 (PDT) Received: from [10.162.42.140] (p8cg001049571a15.blr.arm.com [10.162.42.140]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 158133F718; Fri, 21 Jun 2019 05:52:59 -0700 (PDT) Subject: Re: [PATCH V6 3/3] arm64/mm: Enable memory hot remove To: linux-mm@kvack.org, linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org, akpm@linux-foundation.org, catalin.marinas@arm.com, will.deacon@arm.com Cc: mark.rutland@arm.com, mhocko@suse.com, ira.weiny@intel.com, david@redhat.com, cai@lca.pw, logang@deltatee.com, james.morse@arm.com, cpandya@codeaurora.org, arunks@codeaurora.org, dan.j.williams@intel.com, mgorman@techsingularity.net, osalvador@suse.de, ard.biesheuvel@arm.com, steve.capper@arm.com References: <1560917860-26169-1-git-send-email-anshuman.khandual@arm.com> <1560917860-26169-4-git-send-email-anshuman.khandual@arm.com> From: Anshuman Khandual Message-ID: Date: Fri, 21 Jun 2019 18:23:22 +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: <1560917860-26169-4-git-send-email-anshuman.khandual@arm.com> 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 06/19/2019 09:47 AM, Anshuman Khandual wrote: > +#ifdef CONFIG_MEMORY_HOTPLUG > + /* > + * FIXME: We should have called remove_pagetable(start, end, true). > + * vmemmap and vmalloc virtual range might share intermediate kernel > + * page table entries. Removing vmemmap range page table pages here > + * can potentially conflict with a cuncurrent vmalloc() allocation. > + * > + * This is primarily because valloc() does not take init_mm ptl for > + * the entire page table walk and it's modification. Instead it just > + * takes the lock while allocating and installing page table pages > + * via [p4d|pud|pmd|pte]_aloc(). A cuncurrently vanishing page table > + * entry via memory hotremove can cause vmalloc() kernel page table > + * walk pointers to be invalid on the fly which can cause corruption > + * or worst, a crash. There are couple of typos above which I will fix along with other reviews.