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 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 smtp.lore.kernel.org (Postfix) with ESMTPS id B8B9CCDB474 for ; Tue, 17 Oct 2023 14:06:12 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1qskhj-0004ds-09; Tue, 17 Oct 2023 10:05:51 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qskhf-0004W3-4B for qemu-devel@nongnu.org; Tue, 17 Oct 2023 10:05:48 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.129.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1qskhY-0001Gh-Fs for qemu-devel@nongnu.org; Tue, 17 Oct 2023 10:05:43 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1697551539; h=from:from:reply-to:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type:in-reply-to:in-reply-to: references:references; bh=RRYZc5G0/JAkWv7TvD/5tZrI7QtivRkUrs5iKfysWk0=; b=QFTXoBG/BDt0ikr2fLxTn5KzzsI14b+hNWNwlp+xX0GOwO7tLfTUY+EgvHKwWV+ZMyw1ew mUgdnxCVx6N28drZKAvlZePVCN4BHmcCoJemwyU+/yWuocRtUQObVDU7rJdmc14jak//BI FluxrCaKBsOBOzO0IelT3LZDfTRFaak= Received: from mail-lj1-f197.google.com (mail-lj1-f197.google.com [209.85.208.197]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-575-QrmJqC8qPauBJF3B4gSfhg-1; Tue, 17 Oct 2023 10:05:37 -0400 X-MC-Unique: QrmJqC8qPauBJF3B4gSfhg-1 Received: by mail-lj1-f197.google.com with SMTP id 38308e7fff4ca-2c51a7df557so26961771fa.0 for ; Tue, 17 Oct 2023 07:05:36 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1697551536; x=1698156336; h=mime-version:message-id:date:reply-to:user-agent:references :in-reply-to:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=RRYZc5G0/JAkWv7TvD/5tZrI7QtivRkUrs5iKfysWk0=; b=GsnhOb24O2PY4gY1dXiJLm9JGcmDZiOdKhFfvNiqXiaYyhrAEBVU8WznsU/+jwhS2L 6ANPgeVZGDa4cQ6RawZERSwrJeVBNQz3kIZJ9DMRZm/W5SwAp1R4hBo4TtCTyatzdjcH XpQhXdkTUi4xbqVLuu2uIoVtOc5qAUMwRwg/nQl/1qdTVBl+FX1KFRkHqR9hiy8kxfUU w3hvkzlDx2Zsrdf5+8Nbhit2B1IS9K6rjb+66ZWPOKa8HfEe7a1XZK1WnqQ3AEIMeMO6 NzYxsRv69bIyU4yAq1nOCLal40MnZlT1aif1QyoFJQB8Q2hRepVyo4o+rSw+aq+Om5tF NEZQ== X-Gm-Message-State: AOJu0YzLfDIgEruTNy3dfUaeif2WVORCOI1AOhVuY93z42Bz1bu44Jjs PpQ2M5CrPte6ufFOVAmgz4U4XDS+gwQiBHb1EmiaIyu9nGd7cK+z1I+kTHU9NObpDpMu2D9PNs0 YzlJbSua5lZ85N3k= X-Received: by 2002:a05:651c:3c1:b0:2bc:d634:2210 with SMTP id f1-20020a05651c03c100b002bcd6342210mr1447012ljp.16.1697551535768; Tue, 17 Oct 2023 07:05:35 -0700 (PDT) X-Google-Smtp-Source: AGHT+IEO6MCnbtZu9f7BOZ5msSztNDta83C3an0YvRN7tAt1ksLQpunaJ1+a9gtibpo4WsZN9scbFg== X-Received: by 2002:a05:651c:3c1:b0:2bc:d634:2210 with SMTP id f1-20020a05651c03c100b002bcd6342210mr1446965ljp.16.1697551534547; Tue, 17 Oct 2023 07:05:34 -0700 (PDT) Received: from redhat.com (static-151-150-85-188.ipcom.comunitel.net. [188.85.150.151]) by smtp.gmail.com with ESMTPSA id e13-20020a05600c4e4d00b004065daba6casm10016392wmq.46.2023.10.17.07.05.33 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 17 Oct 2023 07:05:34 -0700 (PDT) From: Juan Quintela To: Peter Xu Cc: qemu-devel@nongnu.org, "Michael S . Tsirkin" , Leonardo Bras , Jiri Denemark , Avihai Horon , Fiona Ebner , Daniel P . =?utf-8?Q?Berrang=C3=A9?= Subject: Re: [PATCH v3 2/3] migration/docs: How to migrate when hosts have different features In-Reply-To: (Peter Xu's message of "Tue, 16 May 2023 19:51:09 -0400") References: <20230515083201.55060-1-quintela@redhat.com> <20230515083201.55060-3-quintela@redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.3 (gnu/linux) Date: Tue, 17 Oct 2023 16:05:33 +0200 Message-ID: <871qdt1h02.fsf@secure.mitica> MIME-Version: 1.0 Content-Type: text/plain Received-SPF: pass client-ip=170.10.129.124; envelope-from=quintela@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.001, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, RCVD_IN_DNSWL_NONE=-0.0001, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: quintela@redhat.com Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Peter Xu wrote: > On Mon, May 15, 2023 at 10:32:00AM +0200, Juan Quintela wrote: >> +$ qemu-system-x86_64 -cpu host,pcid=off,stibp=off >> + >> +Host B: >> + >> +$ qemu-system-x86_64 -cpu host,taa-no=off > > Since we're using cpu as example, shall we at least mention at the end that > we don't suggest using -cpu host if migration is needed? Added something like that. >> + >> +And you would be able to migrate between them. It is responsability >> +of the management application or of the user to make sure that the >> +configuration is correct. QEMU don't know how to look at this kind of >> +features in general. >> + >> +Other devices have worse control about individual features. If they >> +want to be able to migrate between hosts that show different features, >> +the device needs a way to configure which ones it is going to use. >> + >> +In this section we have considered that we are using the same QEMU >> +binary in both sides of the migration. If we use different QEMU >> +versions process, then we need to have into account all other >> +differences and the examples become even more complicated. > > Mostly good to me. What I worry is how much help this will bring to > developers - I'd assume developers working on these will be aware of this. > But I guess it's always good to have any documentation than nothing. I have two hopes here: - when developer finds a problem with migration, they look there. - having a document that I can point when one of this problems happens. What I do now is that I write an email, normally of worse quality and not finding a good example. > Acked-by: Peter Xu Thanks, Juan.