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=-2.5 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 6A01AC43331 for ; Tue, 31 Mar 2020 15:40:26 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (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 31ABD20786 for ; Tue, 31 Mar 2020 15:40:26 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="OV+zqlzl" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 31ABD20786 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:40504 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jJJ05-00019S-Bi for qemu-devel@archiver.kernel.org; Tue, 31 Mar 2020 11:40:25 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:35923) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jJIyz-0008Kv-RG for qemu-devel@nongnu.org; Tue, 31 Mar 2020 11:39:20 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jJIyy-0000Oy-DT for qemu-devel@nongnu.org; Tue, 31 Mar 2020 11:39:17 -0400 Received: from us-smtp-2.mimecast.com ([205.139.110.61]:20181 helo=us-smtp-delivery-1.mimecast.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jJIyy-0000NF-81 for qemu-devel@nongnu.org; Tue, 31 Mar 2020 11:39:16 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585669155; 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=Gmnq5pcGWB04g6GZAPeqqSTgNcroVYBW7kBwmSeKed4=; b=OV+zqlzlbFYUSlx8jfWnPMPJ+S6PjnWM9o/65hPtMXpDNx2Geis5luPFJYRyK3y1cDp4Xk R93Pg2WVkd1XG9XdUfcTs9zNeDmKVeezHUCk0Z+VIZ5ozAnvCuHfgAoHqUexKNbHPUvvu1 B9UXu9Bbn1guQzG+EdkXj8shJYzvMfc= 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-136-QgVHGAObN7CFXb4B1a9bvg-1; Tue, 31 Mar 2020 11:39:12 -0400 X-MC-Unique: QgVHGAObN7CFXb4B1a9bvg-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id E07511005509; Tue, 31 Mar 2020 15:39:10 +0000 (UTC) Received: from [10.36.114.0] (ovpn-114-0.ams2.redhat.com [10.36.114.0]) by smtp.corp.redhat.com (Postfix) with ESMTP id 996A060BFE; Tue, 31 Mar 2020 15:39:08 +0000 (UTC) Subject: Re: [PATCH v1] s390x: Reject unaligned RAM sizes To: Igor Mammedov , Christian Borntraeger References: <20200327152930.66636-1-david@redhat.com> <64cefab8-f1e0-fbc7-27d3-4f28758c595a@de.ibm.com> <24681aa0-9053-238f-89da-8ce08d34241d@de.ibm.com> <20200327174620.06b9c324@redhat.com> <4c5e56fd-a5e2-efe0-9a1a-99acb91aaf71@redhat.com> <20200327231303.30d76ddf@redhat.com> <9ba133fd-603e-a8e1-7a3c-2c05c8653c15@de.ibm.com> <20200331173358.2b195178@redhat.com> 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: <7961ef4f-9bbc-8ac5-f4ff-b4acbd896c99@redhat.com> Date: Tue, 31 Mar 2020 17:39:07 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200331173358.2b195178@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 205.139.110.61 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: =?UTF-8?B?THVrw6HFoSBEb2t0b3I=?= , Thomas Huth , Janosch Frank , Cornelia Huck , Richard Henderson , qemu-devel@nongnu.org, "Dr . David Alan Gilbert" , Halil Pasic , qemu-s390x@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 31.03.20 17:33, Igor Mammedov wrote: > On Tue, 31 Mar 2020 13:17:38 +0200 > Christian Borntraeger wrote: > >> On 27.03.20 23:13, Igor Mammedov wrote: >>> On Fri, 27 Mar 2020 17:53:39 +0100 >>> David Hildenbrand wrote: >>> >>>> On 27.03.20 17:46, Igor Mammedov wrote: >>>>> On Fri, 27 Mar 2020 17:05:34 +0100 >>>>> Christian Borntraeger wrote: >>>>> >>>>>> On 27.03.20 17:01, David Hildenbrand wrote: >>>>>>> On 27.03.20 16:34, Christian Borntraeger wrote: >>>>>>>> >>>>>>>> >>>>>>>> On 27.03.20 16:29, David Hildenbrand wrote: >>>>>>>>> Historically, we fixed up the RAM size (rounded it down), to fit into >>>>>>>>> storage increments. Since commit 3a12fc61af5c ("390x/s390-virtio-ccw: use >>>>>>>>> memdev for RAM"), we no longer consider the fixed-up size when >>>>>>>>> allcoating the RAM block - which will break migration. >>>>>>>>> >>>>>>>>> Let's simply drop that manual fixup code and let the user supply sane >>>>>>>>> RAM sizes. This will bail out early when trying to migrate (and make >>>>>>>>> an existing guest with e.g., 12345 MB non-migratable), but maybe we >>>>>>>>> should have rejected such RAM sizes right from the beginning. >>>>>>>>> >>>>>>>>> As we no longer fixup maxram_size as well, make other users use ram_size >>>>>>>>> instead. Keep using maxram_size when setting the maximum ram size in KVM, >>>>>>>>> as that will come in handy in the future when supporting memory hotplug >>>>>>>>> (in contrast, storage keys and storage attributes for hotplugged memory >>>>>>>>> will have to be migrated per RAM block in the future). >>>>>>>>> >>>>>>>>> This fixes (or rather rejects early): >>>>>>>>> >>>>>>>>> 1. Migrating older QEMU to upstream QEMU (e.g., with "-m 1235M"), as the >>>>>>>>> RAM block size changed. >>>>>>>> >>>>>>>> Not sure I like this variant. Instead of breaking migration (that was >>>>>>>> accidentially done by Igors changes) we now reject migration from older >>>>>>>> QEMUs to 5.0. This is not going to help those that still have such guests >>>>>>>> running and want to migrate. >>>>>>> >>>>>>> As Igor mentioned on another channel, you most probably can migrate an >>>>>>> older guest by starting it on the target with a fixed-up size. >>>>>>> >>>>>>> E.g., migrate an old QEMU "-m 1235M" to a new QEMU "-m 1234M" >>>>>> >>>>>> Yes, that should probably work. >>>>> I'm in process of testing it. >>> >>> it works >>> >>>>> >>>>>>> Not sure how many such weird-size VMs we actually do have in practice. >>>>>> >>>>>> I am worried about some automated deployments where tooling has created >>>>>> these sizes for dozens or hundreds of containers in VMS and so. >>>> >>>> IIRC, e.g., Kata usually uses 2048MB. Not sure about others, but I'd be >>>> surprised if it's not multiples of, say, 128MB. >>>> >>>>> Yep, it's possible but then that tooling/configs should be fixed to work with >>>>> new QEMU that validates user's input. >>>>> >>>> >>>> Yeah, and mention it in the cover letter, +eventually a "fixup" table >>>> (e.g., old_size < X, has to be aligned to Y). >>>> >>>> One alternative is to have an early fixup hack in QEMU, that fixes up >>>> the sizes as we did before (and eventually warns the user). Not sure if >>>> we really want/need that. >>> That would require at least a callback at machine level, >>> also practice shows warnings are of no use. >> >> I would strongly prefer to not break setups that used to work and do an early fixup >> (a machine callback). I will have a look. > > If it were breaking migration stream or guest ABI, > I'd agree with you but it isn't. > > So in this case, it's a bug that qemu wasn't checking > size for alignment and making workaround to keep the bug > around looks wrong to me. > It is fixable on user side (one has to fix VM's config), > so it should be fixed there and not in QEMU. > And any automatic tooling that generates invalid size > should be fixed as well. > (I think it's not QEMU's job to mask users errors and > doing something that user not asked for) Dave G mentioned, that e.g., via Cockpit it can be fairly easy to produce weird RAM sizes (via a slider). So I guess this "issue" could be more widespread than I initially thought. I agree that it's a BUG that we didn't bail out but instead decided to fix it up. -- Thanks, David / dhildenb