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Biederman" , Russell King - ARM Linux admin , Anshuman Khandual , Catalin Marinas , Bhupesh Sharma , kexec@lists.infradead.org, linux-mm@kvack.org, James Morse , Will Deacon , linux-arm-kernel@lists.infradead.org, linuxppc-dev@lists.ozlabs.org, piliu@redhat.com References: <20200414143912.GE4247@MiWiFi-R3L-srv> <0085f460-b0c7-b25f-36a7-fa3bafaab6fe@redhat.com> <20200415023524.GG4247@MiWiFi-R3L-srv> <18cf6afd-c651-25c7-aca3-3ca3c0e07547@redhat.com> <20200416140247.GA12723@MiWiFi-R3L-srv> <4e1546eb-4416-dc6d-d549-62d1cecccbc8@redhat.com> <20200416143634.GH4247@MiWiFi-R3L-srv> <2525cc9c-3566-6275-105b-7f4af8f980bc@redhat.com> <9a4eb1d7-33bf-8707-9c0c-1ca657c3e502@redhat.com> <20200422091718.GT4247@MiWiFi-R3L-srv> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: Date: Wed, 22 Apr 2020 11:24:39 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200422091718.GT4247@MiWiFi-R3L-srv> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 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 22.04.20 11:17, Baoquan He wrote: > On 04/21/20 at 03:29pm, David Hildenbrand wrote: >>>> ACPI SRAT is embeded into efi, need read out the rsdp pointer. If we don't >>>> pass the efi, it won't get the SRAT table correctly, if I remember >>>> correctly. Yeah, I remeber kvm guest can get memory hotplugged with >>>> ACPI only, this won't happen on bare metal though. Need check carefully. >>>> I have been using kvm guest with uefi firmwire recently. >>> >>> Yeah, I can imagine that bare metal is different. kvm only uses ACPI. >>> >>> I'm also asking because of virtio-mem. Memory added via virtio-mem is >>> not part of any efi tables or whatsoever. So I assume the kexec kernel >>> will not detect it automatically (good!), instead load the virtio-mem >>> driver and let it add memory back to the system. >>> >>> I should probably play with kexec and virtio-mem once I have some spare >>> cycles ... to find out what's broken and needs to be addressed :) >> >> FWIW, I just gave virtio-mem and kexec/kdump a try. >> >> a) kdump seems to work. Memory added by virtio-mem is getting dumped. >> The kexec kernel only uses memory in the crash region. The virtio-mem >> driver properly bails out due to is_kdump_kernel(). > > Right, kdump is not impacted later added memory. > >> >> b) "kexec -s -l" seems to work fine. For now, the kernel does not seem >> to get placed on virtio-mem memory (pure luck due to the left-to-right >> search). Memory added by virtio-mem is not getting added to the e820 >> map. Once the virtio-mem driver comes back up in the kexec kernel, the >> right memory is readded. > > kexec_file_load just behaves as you tested. It doesn't collect later > added memory to e820 because it uses e820_table_kexec directly to pass > e820 to kexec-ed kernel. However, this e820_table_kexec is only updated > during boot stage. I tried hot adding DIMM after boot, kexec-ed kernel > doesn't have it in e820 during bootup, but it's recoginized and added > when ACPI scanning. I think we should update e820_table_kexec when hot > add/remove memory, at least for DIMM. Not sure if DLPAR, virtio-mem, > balloon will need be added into e820_table_kexec too, and if this is > expected behaviour. > > But whatever we do, it won't impact the kexec file_loading, because of > the searching strategy bottom up. Just adding them into e820_table_kexec > will make it consistent with cold reboot which get recognizes and get > them into e820 during bootup. Yeah, I think whatever a cold-booted kernel will see is what kexec-ed kernel should see. Not more, not less. Regarding virtio-mem: Not in e820 on cold-boot. Regarding DIMMs: DIMMs under KVM will never show up in the e820 map IIRC. I think on real HW it can be different. -- Thanks, David / dhildenb From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.0 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id BC957C5518A for ; Wed, 22 Apr 2020 09:27:04 +0000 (UTC) Received: from lists.ozlabs.org (lists.ozlabs.org [203.11.71.2]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 6FC532073A for ; Wed, 22 Apr 2020 09:27:04 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="Taxtm86O"; 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Wed, 22 Apr 2020 09:24:43 +0000 (UTC) Received: from [10.36.114.57] (ovpn-114-57.ams2.redhat.com [10.36.114.57]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6C7CC5DA82; Wed, 22 Apr 2020 09:24:40 +0000 (UTC) Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image To: Baoquan He References: <20200414143912.GE4247@MiWiFi-R3L-srv> <0085f460-b0c7-b25f-36a7-fa3bafaab6fe@redhat.com> <20200415023524.GG4247@MiWiFi-R3L-srv> <18cf6afd-c651-25c7-aca3-3ca3c0e07547@redhat.com> <20200416140247.GA12723@MiWiFi-R3L-srv> <4e1546eb-4416-dc6d-d549-62d1cecccbc8@redhat.com> <20200416143634.GH4247@MiWiFi-R3L-srv> <2525cc9c-3566-6275-105b-7f4af8f980bc@redhat.com> <9a4eb1d7-33bf-8707-9c0c-1ca657c3e502@redhat.com> <20200422091718.GT4247@MiWiFi-R3L-srv> From: David Hildenbrand Autocrypt: addr=david@redhat.com; prefer-encrypt=mutual; keydata= mQINBFXLn5EBEAC+zYvAFJxCBY9Tr1xZgcESmxVNI/0ffzE/ZQOiHJl6mGkmA1R7/uUpiCjJ dBrn+lhhOYjjNefFQou6478faXE6o2AhmebqT4KiQoUQFV4R7y1KMEKoSyy8hQaK1umALTdL QZLQMzNE74ap+GDK0wnacPQFpcG1AE9RMq3aeErY5tujekBS32jfC/7AnH7I0v1v1TbbK3Gp XNeiN4QroO+5qaSr0ID2sz5jtBLRb15RMre27E1ImpaIv2Jw8NJgW0k/D1RyKCwaTsgRdwuK Kx/Y91XuSBdz0uOyU/S8kM1+ag0wvsGlpBVxRR/xw/E8M7TEwuCZQArqqTCmkG6HGcXFT0V9 PXFNNgV5jXMQRwU0O/ztJIQqsE5LsUomE//bLwzj9IVsaQpKDqW6TAPjcdBDPLHvriq7kGjt WhVhdl0qEYB8lkBEU7V2Yb+SYhmhpDrti9Fq1EsmhiHSkxJcGREoMK/63r9WLZYI3+4W2rAc UucZa4OT27U5ZISjNg3Ev0rxU5UH2/pT4wJCfxwocmqaRr6UYmrtZmND89X0KigoFD/XSeVv jwBRNjPAubK9/k5NoRrYqztM9W6sJqrH8+UWZ1Idd/DdmogJh0gNC0+N42Za9yBRURfIdKSb B3JfpUqcWwE7vUaYrHG1nw54pLUoPG6sAA7Mehl3nd4pZUALHwARAQABtCREYXZpZCBIaWxk ZW5icmFuZCA8ZGF2aWRAcmVkaGF0LmNvbT6JAlgEEwEIAEICGwMFCQlmAYAGCwkIBwMCBhUI AgkKCwQWAgMBAh4BAheAFiEEG9nKrXNcTDpGDfzKTd4Q9wD/g1oFAl3pImkCGQEACgkQTd4Q 9wD/g1o+VA//SFvIHUAvul05u6wKv/pIR6aICPdpF9EIgEU448g+7FfDgQwcEny1pbEzAmiw zAXIQ9H0NZh96lcq+yDLtONnXk/bEYWHHUA014A1wqcYNRY8RvY1+eVHb0uu0KYQoXkzvu+s Dncuguk470XPnscL27hs8PgOP6QjG4jt75K2LfZ0eAqTOUCZTJxA8A7E9+XTYuU0hs7QVrWJ jQdFxQbRMrYz7uP8KmTK9/Cnvqehgl4EzyRaZppshruKMeyheBgvgJd5On1wWq4ZUV5PFM4x II3QbD3EJfWbaJMR55jI9dMFa+vK7MFz3rhWOkEx/QR959lfdRSTXdxs8V3zDvChcmRVGN8U Vo93d1YNtWnA9w6oCW1dnDZ4kgQZZSBIjp6iHcA08apzh7DPi08jL7M9UQByeYGr8KuR4i6e RZI6xhlZerUScVzn35ONwOC91VdYiQgjemiVLq1WDDZ3B7DIzUZ4RQTOaIWdtXBWb8zWakt/ ztGhsx0e39Gvt3391O1PgcA7ilhvqrBPemJrlb9xSPPRbaNAW39P8ws/UJnzSJqnHMVxbRZC Am4add/SM+OCP0w3xYss1jy9T+XdZa0lhUvJfLy7tNcjVG/sxkBXOaSC24MFPuwnoC9WvCVQ ZBxouph3kqc4Dt5X1EeXVLeba+466P1fe1rC8MbcwDkoUo65Ag0EVcufkQEQAOfX3n0g0fZz Bgm/S2zF/kxQKCEKP8ID+Vz8sy2GpDvveBq4H2Y34XWsT1zLJdvqPI4af4ZSMxuerWjXbVWb T6d4odQIG0fKx4F8NccDqbgHeZRNajXeeJ3R7gAzvWvQNLz4piHrO/B4tf8svmRBL0ZB5P5A 2uhdwLU3NZuK22zpNn4is87BPWF8HhY0L5fafgDMOqnf4guJVJPYNPhUFzXUbPqOKOkL8ojk CXxkOFHAbjstSK5Ca3fKquY3rdX3DNo+EL7FvAiw1mUtS+5GeYE+RMnDCsVFm/C7kY8c2d0G NWkB9pJM5+mnIoFNxy7YBcldYATVeOHoY4LyaUWNnAvFYWp08dHWfZo9WCiJMuTfgtH9tc75 7QanMVdPt6fDK8UUXIBLQ2TWr/sQKE9xtFuEmoQGlE1l6bGaDnnMLcYu+Asp3kDT0w4zYGsx 5r6XQVRH4+5N6eHZiaeYtFOujp5n+pjBaQK7wUUjDilPQ5QMzIuCL4YjVoylWiBNknvQWBXS lQCWmavOT9sttGQXdPCC5ynI+1ymZC1ORZKANLnRAb0NH/UCzcsstw2TAkFnMEbo9Zu9w7Kv AxBQXWeXhJI9XQssfrf4Gusdqx8nPEpfOqCtbbwJMATbHyqLt7/oz/5deGuwxgb65pWIzufa N7eop7uh+6bezi+rugUI+w6DABEBAAGJAiUEGAECAA8FAlXLn5ECGwwFCQlmAYAACgkQTd4Q 9wD/g1qA6w/+M+ggFv+JdVsz5+ZIc6MSyGUozASX+bmIuPeIecc9UsFRatc91LuJCKMkD9Uv GOcWSeFpLrSGRQ1Z7EMzFVU//qVs6uzhsNk0RYMyS0B6oloW3FpyQ+zOVylFWQCzoyyf227y GW8HnXunJSC+4PtlL2AY4yZjAVAPLK2l6mhgClVXTQ/S7cBoTQKP+jvVJOoYkpnFxWE9pn4t H5QIFk7Ip8TKr5k3fXVWk4lnUi9MTF/5L/mWqdyIO1s7cjharQCstfWCzWrVeVctpVoDfJWp 4LwTuQ5yEM2KcPeElLg5fR7WB2zH97oI6/Ko2DlovmfQqXh9xWozQt0iGy5tWzh6I0JrlcxJ ileZWLccC4XKD1037Hy2FLAjzfoWgwBLA6ULu0exOOdIa58H4PsXtkFPrUF980EEibUp0zFz GotRVekFAceUaRvAj7dh76cToeZkfsjAvBVb4COXuhgX6N4pofgNkW2AtgYu1nUsPAo+NftU CxrhjHtLn4QEBpkbErnXQyMjHpIatlYGutVMS91XTQXYydCh5crMPs7hYVsvnmGHIaB9ZMfB njnuI31KBiLUks+paRkHQlFcgS2N3gkRBzH7xSZ+t7Re3jvXdXEzKBbQ+dC3lpJB0wPnyMcX FOTT3aZT7IgePkt5iC/BKBk3hqKteTnJFeVIT7EC+a6YUFg= Organization: Red Hat GmbH Message-ID: Date: Wed, 22 Apr 2020 11:24:39 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200422091718.GT4247@MiWiFi-R3L-srv> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-BeenThere: linuxppc-dev@lists.ozlabs.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Linux on PowerPC Developers Mail List 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 Errors-To: linuxppc-dev-bounces+linuxppc-dev=archiver.kernel.org@lists.ozlabs.org Sender: "Linuxppc-dev" On 22.04.20 11:17, Baoquan He wrote: > On 04/21/20 at 03:29pm, David Hildenbrand wrote: >>>> ACPI SRAT is embeded into efi, need read out the rsdp pointer. If we don't >>>> pass the efi, it won't get the SRAT table correctly, if I remember >>>> correctly. Yeah, I remeber kvm guest can get memory hotplugged with >>>> ACPI only, this won't happen on bare metal though. Need check carefully. >>>> I have been using kvm guest with uefi firmwire recently. >>> >>> Yeah, I can imagine that bare metal is different. kvm only uses ACPI. >>> >>> I'm also asking because of virtio-mem. Memory added via virtio-mem is >>> not part of any efi tables or whatsoever. So I assume the kexec kernel >>> will not detect it automatically (good!), instead load the virtio-mem >>> driver and let it add memory back to the system. >>> >>> I should probably play with kexec and virtio-mem once I have some spare >>> cycles ... to find out what's broken and needs to be addressed :) >> >> FWIW, I just gave virtio-mem and kexec/kdump a try. >> >> a) kdump seems to work. Memory added by virtio-mem is getting dumped. >> The kexec kernel only uses memory in the crash region. The virtio-mem >> driver properly bails out due to is_kdump_kernel(). > > Right, kdump is not impacted later added memory. > >> >> b) "kexec -s -l" seems to work fine. For now, the kernel does not seem >> to get placed on virtio-mem memory (pure luck due to the left-to-right >> search). Memory added by virtio-mem is not getting added to the e820 >> map. Once the virtio-mem driver comes back up in the kexec kernel, the >> right memory is readded. > > kexec_file_load just behaves as you tested. It doesn't collect later > added memory to e820 because it uses e820_table_kexec directly to pass > e820 to kexec-ed kernel. However, this e820_table_kexec is only updated > during boot stage. I tried hot adding DIMM after boot, kexec-ed kernel > doesn't have it in e820 during bootup, but it's recoginized and added > when ACPI scanning. I think we should update e820_table_kexec when hot > add/remove memory, at least for DIMM. Not sure if DLPAR, virtio-mem, > balloon will need be added into e820_table_kexec too, and if this is > expected behaviour. > > But whatever we do, it won't impact the kexec file_loading, because of > the searching strategy bottom up. Just adding them into e820_table_kexec > will make it consistent with cold reboot which get recognizes and get > them into e820 during bootup. Yeah, I think whatever a cold-booted kernel will see is what kexec-ed kernel should see. Not more, not less. Regarding virtio-mem: Not in e820 on cold-boot. Regarding DIMMs: DIMMs under KVM will never show up in the e820 map IIRC. I think on real HW it can be different. -- Thanks, David / dhildenb From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.2 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 32FEFC55186 for ; Wed, 22 Apr 2020 09:25:08 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 520012076A for ; Wed, 22 Apr 2020 09:25:07 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="Jeox3ZKs"; 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Wed, 22 Apr 2020 05:24:45 -0400 X-MC-Unique: cePc8J72MHiLls8ayhdEgQ-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 5C2321007281; Wed, 22 Apr 2020 09:24:43 +0000 (UTC) Received: from [10.36.114.57] (ovpn-114-57.ams2.redhat.com [10.36.114.57]) by smtp.corp.redhat.com (Postfix) with ESMTP id 6C7CC5DA82; Wed, 22 Apr 2020 09:24:40 +0000 (UTC) Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image To: Baoquan He References: <20200414143912.GE4247@MiWiFi-R3L-srv> <0085f460-b0c7-b25f-36a7-fa3bafaab6fe@redhat.com> <20200415023524.GG4247@MiWiFi-R3L-srv> <18cf6afd-c651-25c7-aca3-3ca3c0e07547@redhat.com> <20200416140247.GA12723@MiWiFi-R3L-srv> <4e1546eb-4416-dc6d-d549-62d1cecccbc8@redhat.com> <20200416143634.GH4247@MiWiFi-R3L-srv> <2525cc9c-3566-6275-105b-7f4af8f980bc@redhat.com> <9a4eb1d7-33bf-8707-9c0c-1ca657c3e502@redhat.com> <20200422091718.GT4247@MiWiFi-R3L-srv> From: David Hildenbrand Autocrypt: addr=david@redhat.com; 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Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.7.0 MIME-Version: 1.0 In-Reply-To: <20200422091718.GT4247@MiWiFi-R3L-srv> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 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-20200422_022450_932477_163DFFDB X-CRM114-Status: GOOD ( 20.50 ) 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 On 22.04.20 11:17, Baoquan He wrote: > On 04/21/20 at 03:29pm, David Hildenbrand wrote: >>>> ACPI SRAT is embeded into efi, need read out the rsdp pointer. If we don't >>>> pass the efi, it won't get the SRAT table correctly, if I remember >>>> correctly. Yeah, I remeber kvm guest can get memory hotplugged with >>>> ACPI only, this won't happen on bare metal though. Need check carefully. >>>> I have been using kvm guest with uefi firmwire recently. >>> >>> Yeah, I can imagine that bare metal is different. kvm only uses ACPI. >>> >>> I'm also asking because of virtio-mem. Memory added via virtio-mem is >>> not part of any efi tables or whatsoever. So I assume the kexec kernel >>> will not detect it automatically (good!), instead load the virtio-mem >>> driver and let it add memory back to the system. >>> >>> I should probably play with kexec and virtio-mem once I have some spare >>> cycles ... to find out what's broken and needs to be addressed :) >> >> FWIW, I just gave virtio-mem and kexec/kdump a try. >> >> a) kdump seems to work. Memory added by virtio-mem is getting dumped. >> The kexec kernel only uses memory in the crash region. The virtio-mem >> driver properly bails out due to is_kdump_kernel(). > > Right, kdump is not impacted later added memory. > >> >> b) "kexec -s -l" seems to work fine. For now, the kernel does not seem >> to get placed on virtio-mem memory (pure luck due to the left-to-right >> search). Memory added by virtio-mem is not getting added to the e820 >> map. Once the virtio-mem driver comes back up in the kexec kernel, the >> right memory is readded. > > kexec_file_load just behaves as you tested. It doesn't collect later > added memory to e820 because it uses e820_table_kexec directly to pass > e820 to kexec-ed kernel. However, this e820_table_kexec is only updated > during boot stage. I tried hot adding DIMM after boot, kexec-ed kernel > doesn't have it in e820 during bootup, but it's recoginized and added > when ACPI scanning. I think we should update e820_table_kexec when hot > add/remove memory, at least for DIMM. Not sure if DLPAR, virtio-mem, > balloon will need be added into e820_table_kexec too, and if this is > expected behaviour. > > But whatever we do, it won't impact the kexec file_loading, because of > the searching strategy bottom up. Just adding them into e820_table_kexec > will make it consistent with cold reboot which get recognizes and get > them into e820 during bootup. Yeah, I think whatever a cold-booted kernel will see is what kexec-ed kernel should see. Not more, not less. Regarding virtio-mem: Not in e820 on cold-boot. Regarding DIMMs: DIMMs under KVM will never show up in the e820 map IIRC. I think on real HW it can be different. -- Thanks, David / dhildenb _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from us-smtp-1.mimecast.com ([207.211.31.81] helo=us-smtp-delivery-1.mimecast.com) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jRBch-0006x9-64 for kexec@lists.infradead.org; Wed, 22 Apr 2020 09:24:54 +0000 Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image References: <20200414143912.GE4247@MiWiFi-R3L-srv> <0085f460-b0c7-b25f-36a7-fa3bafaab6fe@redhat.com> <20200415023524.GG4247@MiWiFi-R3L-srv> <18cf6afd-c651-25c7-aca3-3ca3c0e07547@redhat.com> <20200416140247.GA12723@MiWiFi-R3L-srv> <4e1546eb-4416-dc6d-d549-62d1cecccbc8@redhat.com> <20200416143634.GH4247@MiWiFi-R3L-srv> <2525cc9c-3566-6275-105b-7f4af8f980bc@redhat.com> <9a4eb1d7-33bf-8707-9c0c-1ca657c3e502@redhat.com> <20200422091718.GT4247@MiWiFi-R3L-srv> From: David Hildenbrand Message-ID: Date: Wed, 22 Apr 2020 11:24:39 +0200 MIME-Version: 1.0 In-Reply-To: <20200422091718.GT4247@MiWiFi-R3L-srv> Content-Language: en-US List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Baoquan He 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 On 22.04.20 11:17, Baoquan He wrote: > On 04/21/20 at 03:29pm, David Hildenbrand wrote: >>>> ACPI SRAT is embeded into efi, need read out the rsdp pointer. If we don't >>>> pass the efi, it won't get the SRAT table correctly, if I remember >>>> correctly. Yeah, I remeber kvm guest can get memory hotplugged with >>>> ACPI only, this won't happen on bare metal though. Need check carefully. >>>> I have been using kvm guest with uefi firmwire recently. >>> >>> Yeah, I can imagine that bare metal is different. kvm only uses ACPI. >>> >>> I'm also asking because of virtio-mem. Memory added via virtio-mem is >>> not part of any efi tables or whatsoever. So I assume the kexec kernel >>> will not detect it automatically (good!), instead load the virtio-mem >>> driver and let it add memory back to the system. >>> >>> I should probably play with kexec and virtio-mem once I have some spare >>> cycles ... to find out what's broken and needs to be addressed :) >> >> FWIW, I just gave virtio-mem and kexec/kdump a try. >> >> a) kdump seems to work. Memory added by virtio-mem is getting dumped. >> The kexec kernel only uses memory in the crash region. The virtio-mem >> driver properly bails out due to is_kdump_kernel(). > > Right, kdump is not impacted later added memory. > >> >> b) "kexec -s -l" seems to work fine. For now, the kernel does not seem >> to get placed on virtio-mem memory (pure luck due to the left-to-right >> search). Memory added by virtio-mem is not getting added to the e820 >> map. Once the virtio-mem driver comes back up in the kexec kernel, the >> right memory is readded. > > kexec_file_load just behaves as you tested. It doesn't collect later > added memory to e820 because it uses e820_table_kexec directly to pass > e820 to kexec-ed kernel. However, this e820_table_kexec is only updated > during boot stage. I tried hot adding DIMM after boot, kexec-ed kernel > doesn't have it in e820 during bootup, but it's recoginized and added > when ACPI scanning. I think we should update e820_table_kexec when hot > add/remove memory, at least for DIMM. Not sure if DLPAR, virtio-mem, > balloon will need be added into e820_table_kexec too, and if this is > expected behaviour. > > But whatever we do, it won't impact the kexec file_loading, because of > the searching strategy bottom up. Just adding them into e820_table_kexec > will make it consistent with cold reboot which get recognizes and get > them into e820 during bootup. Yeah, I think whatever a cold-booted kernel will see is what kexec-ed kernel should see. Not more, not less. Regarding virtio-mem: Not in e820 on cold-boot. Regarding DIMMs: DIMMs under KVM will never show up in the e820 map IIRC. I think on real HW it can be different. -- Thanks, David / dhildenb _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec