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=-2.4 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 6C6A5C55189 for ; Wed, 22 Apr 2020 10:05:52 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 10F1320774 for ; Wed, 22 Apr 2020 10:05:52 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="E2vPty66" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 10F1320774 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id A39BE8E0007; Wed, 22 Apr 2020 06:05:51 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9EAE48E0003; Wed, 22 Apr 2020 06:05:51 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 8B3248E0007; Wed, 22 Apr 2020 06:05:51 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0101.hostedemail.com [216.40.44.101]) by kanga.kvack.org (Postfix) with ESMTP id 7183E8E0003 for ; Wed, 22 Apr 2020 06:05:51 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay04.hostedemail.com (Postfix) with ESMTP id 39AB2281F for ; Wed, 22 Apr 2020 10:05:51 +0000 (UTC) X-FDA: 76735059702.22.tail15_8a58f0e37b341 X-HE-Tag: tail15_8a58f0e37b341 X-Filterd-Recvd-Size: 10848 Received: from us-smtp-delivery-1.mimecast.com (us-smtp-2.mimecast.com [207.211.31.81]) by imf39.hostedemail.com (Postfix) with ESMTP for ; Wed, 22 Apr 2020 10:05:50 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1587549950; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:autocrypt:autocrypt; bh=rATKYts2554mzs5OMKZzueMwerGodqJQMSarGToJc4M=; b=E2vPty66eyh8RXmW9wDUnjboLxgp0K3IhXwrucgS5O9Ex++sHYKmGdtED7/pb/SKF0SG5q JSuZfcSyX0c0QSjJFMGCP5IojKCEvhTWwL2RhoxHiWn58msexKpSQSRnf3mufMTZsu+Sq2 3iP3NBfA1VOgmV0ijlI1S3bQ7vxR3Xc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-323-3QDnJ9pxOSi9dKLdBNAUfQ-1; Wed, 22 Apr 2020 06:05:47 -0400 X-MC-Unique: 3QDnJ9pxOSi9dKLdBNAUfQ-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 0C9688018A6; Wed, 22 Apr 2020 10:05:46 +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 156E71009940; Wed, 22 Apr 2020 10:05:40 +0000 (UTC) Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image To: Baoquan He Cc: Andrew Morton , "Eric W. 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: <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> <20200422095733.GU4247@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 12:05:40 +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: <20200422095733.GU4247@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 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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 11:57, Baoquan He wrote: > On 04/22/20 at 11:24am, David Hildenbrand wrote: >> 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 carefu= lly.=20 >>>>>> 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 kerne= l >>>>> 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 spa= re >>>>> 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_kexe= c >>> 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. >=20 > Yeah, DIMMs under KVM won't show up in e820 map. While this is not featur= e > of QEMU/KVM, but a defect of it. I ever asked Igor who is developer of > QEMU/KVM guest in this area, why we don't make kvm guest recognize > hotpluggable DIMM and add it into e820 map, he said he had tried to make > it, but this will corrupt guest on HyperV. So he had to revert the Yeah, I remember that this had to be reverted due to something breaking. But OTOH, it allows us to online coldplugged DIMMs online_movable easily, so I'd say it's even a feature (although, does not behave like real HW we have). I use this extensively when testing memory hot(un)plug via coldplugged DIMMs. I do wonder if there is real HW, where this is also the case. > commit on qemu. So I think we can leave it for now for both real HW and > kvm, or update the e820_table_kexec to include added DIMM for both real > HW and KVM. I hope one day KVM dev will find a way to conquer the defect > on HyperV and make the e820map consistent with bare metal. After all, > kvm guest is trying to imitate real HW for the most part. >=20 > Anyway, I will think about the e820_table_kexec updating. See if we can > do something about it. Yeah, for DIMMs on real HW it might definitely make sense. We might be able to hook into updates of /sys/firmware/memmap on memory add/remove. --=20 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 A30C6C5518A for ; Wed, 22 Apr 2020 10:09:04 +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 576D22077D for ; Wed, 22 Apr 2020 10:09:04 +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="E2vPty66"; 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Wed, 22 Apr 2020 10:05:46 +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 156E71009940; Wed, 22 Apr 2020 10:05:40 +0000 (UTC) Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image To: Baoquan He References: <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> <20200422095733.GU4247@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 12:05:40 +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: <20200422095733.GU4247@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 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable 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 11:57, Baoquan He wrote: > On 04/22/20 at 11:24am, David Hildenbrand wrote: >> 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 carefu= lly.=20 >>>>>> 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 kerne= l >>>>> 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 spa= re >>>>> 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_kexe= c >>> 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. >=20 > Yeah, DIMMs under KVM won't show up in e820 map. While this is not featur= e > of QEMU/KVM, but a defect of it. I ever asked Igor who is developer of > QEMU/KVM guest in this area, why we don't make kvm guest recognize > hotpluggable DIMM and add it into e820 map, he said he had tried to make > it, but this will corrupt guest on HyperV. So he had to revert the Yeah, I remember that this had to be reverted due to something breaking. But OTOH, it allows us to online coldplugged DIMMs online_movable easily, so I'd say it's even a feature (although, does not behave like real HW we have). I use this extensively when testing memory hot(un)plug via coldplugged DIMMs. I do wonder if there is real HW, where this is also the case. > commit on qemu. So I think we can leave it for now for both real HW and > kvm, or update the e820_table_kexec to include added DIMM for both real > HW and KVM. I hope one day KVM dev will find a way to conquer the defect > on HyperV and make the e820map consistent with bare metal. After all, > kvm guest is trying to imitate real HW for the most part. >=20 > Anyway, I will think about the e820_table_kexec updating. See if we can > do something about it. Yeah, for DIMMs on real HW it might definitely make sense. We might be able to hook into updates of /sys/firmware/memmap on memory add/remove. --=20 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=-2.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,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 7F47EC5518E for ; Wed, 22 Apr 2020 10:05:55 +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 49C3520774 for ; Wed, 22 Apr 2020 10:05:55 +0000 (UTC) Authentication-Results: mail.kernel.org; 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bh=rATKYts2554mzs5OMKZzueMwerGodqJQMSarGToJc4M=; b=E2vPty66eyh8RXmW9wDUnjboLxgp0K3IhXwrucgS5O9Ex++sHYKmGdtED7/pb/SKF0SG5q JSuZfcSyX0c0QSjJFMGCP5IojKCEvhTWwL2RhoxHiWn58msexKpSQSRnf3mufMTZsu+Sq2 3iP3NBfA1VOgmV0ijlI1S3bQ7vxR3Xc= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-323-3QDnJ9pxOSi9dKLdBNAUfQ-1; Wed, 22 Apr 2020 06:05:47 -0400 X-MC-Unique: 3QDnJ9pxOSi9dKLdBNAUfQ-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 0C9688018A6; Wed, 22 Apr 2020 10:05:46 +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 156E71009940; Wed, 22 Apr 2020 10:05:40 +0000 (UTC) Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image To: Baoquan He References: <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> <20200422095733.GU4247@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: <20200422095733.GU4247@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-20200422_030551_406039_824B7CC3 X-CRM114-Status: GOOD ( 24.34 ) 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 11:57, Baoquan He wrote: > On 04/22/20 at 11:24am, David Hildenbrand wrote: >> 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. > > Yeah, DIMMs under KVM won't show up in e820 map. While this is not feature > of QEMU/KVM, but a defect of it. I ever asked Igor who is developer of > QEMU/KVM guest in this area, why we don't make kvm guest recognize > hotpluggable DIMM and add it into e820 map, he said he had tried to make > it, but this will corrupt guest on HyperV. So he had to revert the Yeah, I remember that this had to be reverted due to something breaking. But OTOH, it allows us to online coldplugged DIMMs online_movable easily, so I'd say it's even a feature (although, does not behave like real HW we have). I use this extensively when testing memory hot(un)plug via coldplugged DIMMs. I do wonder if there is real HW, where this is also the case. > commit on qemu. So I think we can leave it for now for both real HW and > kvm, or update the e820_table_kexec to include added DIMM for both real > HW and KVM. I hope one day KVM dev will find a way to conquer the defect > on HyperV and make the e820map consistent with bare metal. After all, > kvm guest is trying to imitate real HW for the most part. > > Anyway, I will think about the e820_table_kexec updating. See if we can > do something about it. Yeah, for DIMMs on real HW it might definitely make sense. We might be able to hook into updates of /sys/firmware/memmap on memory add/remove. -- 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-delivery-1.mimecast.com ([207.211.31.120] helo=us-smtp-1.mimecast.com) by bombadil.infradead.org with esmtps (Exim 4.92.3 #3 (Red Hat Linux)) id 1jRCGN-0008Cb-Cx for kexec@lists.infradead.org; Wed, 22 Apr 2020 10:05:52 +0000 Subject: Re: [PATCH 1/3] kexec: Prevent removal of memory in use by a loaded kexec image References: <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> <20200422095733.GU4247@MiWiFi-R3L-srv> From: David Hildenbrand Message-ID: Date: Wed, 22 Apr 2020 12:05:40 +0200 MIME-Version: 1.0 In-Reply-To: <20200422095733.GU4247@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 11:57, Baoquan He wrote: > On 04/22/20 at 11:24am, David Hildenbrand wrote: >> 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. > > Yeah, DIMMs under KVM won't show up in e820 map. While this is not feature > of QEMU/KVM, but a defect of it. I ever asked Igor who is developer of > QEMU/KVM guest in this area, why we don't make kvm guest recognize > hotpluggable DIMM and add it into e820 map, he said he had tried to make > it, but this will corrupt guest on HyperV. So he had to revert the Yeah, I remember that this had to be reverted due to something breaking. But OTOH, it allows us to online coldplugged DIMMs online_movable easily, so I'd say it's even a feature (although, does not behave like real HW we have). I use this extensively when testing memory hot(un)plug via coldplugged DIMMs. I do wonder if there is real HW, where this is also the case. > commit on qemu. So I think we can leave it for now for both real HW and > kvm, or update the e820_table_kexec to include added DIMM for both real > HW and KVM. I hope one day KVM dev will find a way to conquer the defect > on HyperV and make the e820map consistent with bare metal. After all, > kvm guest is trying to imitate real HW for the most part. > > Anyway, I will think about the e820_table_kexec updating. See if we can > do something about it. Yeah, for DIMMs on real HW it might definitely make sense. We might be able to hook into updates of /sys/firmware/memmap on memory add/remove. -- Thanks, David / dhildenb _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec