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Thu, 16 Apr 2020 09:31:47 -0400 X-MC-Unique: rRaJvKTfNt6WWMMWT6zGFQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id EF0AC806E06; Thu, 16 Apr 2020 13:31:44 +0000 (UTC) Received: from [10.36.114.9] (ovpn-114-9.ams2.redhat.com [10.36.114.9]) by smtp.corp.redhat.com (Postfix) with ESMTP id 8B098100164D; Thu, 16 Apr 2020 13:31:41 +0000 (UTC) Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image To: Baoquan He References: <20200412080836.GM25745@shell.armlinux.org.uk> <87wo6klbw0.fsf@x220.int.ebiederm.org> <20200413023701.GA20265@MiWiFi-R3L-srv> <871rorjzmc.fsf@x220.int.ebiederm.org> <20200414064031.GB4247@MiWiFi-R3L-srv> <86e96214-7053-340b-5c1a-ff97fb94d8e0@redhat.com> <20200414092201.GD4247@MiWiFi-R3L-srv> <20200414143912.GE4247@MiWiFi-R3L-srv> <0085f460-b0c7-b25f-36a7-fa3bafaab6fe@redhat.com> <20200415023524.GG4247@MiWiFi-R3L-srv> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200415023524.GG4247@MiWiFi-R3L-srv> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20200416_063154_125110_578B7C48 X-CRM114-Status: GOOD ( 17.62 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: piliu@redhat.com, Anshuman Khandual , Catalin Marinas , Bhupesh Sharma , linuxppc-dev@lists.ozlabs.org, kexec@lists.infradead.org, Russell King - ARM Linux admin , linux-mm@kvack.org, James Morse , "Eric W. Biederman" , Andrew Morton , Will Deacon , linux-arm-kernel@lists.infradead.org Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org > Not sure if I get the notifier idea clearly. If you mean > > 1) Add a common function to pick memory in unmovable zone; Not strictly required IMHO. But, minor detail. > 2) Let DLPAR, balloon register with notifier; Yeah, or virtio-mem, or any other technology that adds/removes memory dynamically. > 3) In the common function, ask notified part to check if the picked > unmovable memory is available for locating kexec kernel; Yeah. > > Sounds doable to me, and not complicated. > >> images. It would apply to >> >> - arm64 and filter out all hotadded memory (IIRC, only boot memory can >> be used). > > Do you mean hot added memory after boot can't be recognized and added > into system RAM on arm64? See patch #3 of this patch set, which wants to avoid placing kexec binaries on hotplugged memory. But I have no idea what the current plan regarding arm64 is (this thread exploded :) ). I would assume that we don't want to place kexec images on any hotplugged (or rather: hot(un)pluggable) memory - on any architecture. > > >> - powerpc to filter out all LMBs that can be removed (assuming not all >> memory corresponds to LMBs that can be removed, otherwise we're in >> trouble ... :) ) >> - virtio-mem to filter out all memory it added. >> - hyper-v to filter out partially backed memory blocks (esp. the last >> memory block it added and only partially backed it by memory). >> >> This would make it work for kexec_file_load(), however, I do wonder how >> we would want to approach that from userspace kexec-tools when handling >> it from kexec_load(). > > Let's make kexec_file_load work firstly. Since this work is only first > step to make kexec-ed kernel not break memory hotplug. After kexec > rebooting, the KASLR may locate kernel into hotpluggable area too. Can you elaborate how that would work? -- Thanks, David / dhildenb _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel