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=-5.0 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,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 5166CC433ED for ; Thu, 15 Apr 2021 17:03:30 +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 F3F3E611AC for ; Thu, 15 Apr 2021 17:03:29 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org F3F3E611AC 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]:57346 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lX5Or-0001yU-0r for qemu-devel@archiver.kernel.org; Thu, 15 Apr 2021 13:03:29 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:43184) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lX530-0008AL-Ny for qemu-devel@nongnu.org; Thu, 15 Apr 2021 12:40:56 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]:42152) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lX52u-0000HH-BU for qemu-devel@nongnu.org; Thu, 15 Apr 2021 12:40:54 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1618504847; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=n8k5ujv+dftCUrvcY6gwlX+AmAxPRZdv8dO3XK2ULv0=; b=AzfQXVOp21WZnO0TYntkKtdtPG+PJGDqUVeByX2LDzTfzhcyoN5WAZGFbrdqab2i37tKkC OkYG5lEV0DTEfu2D/uE5Cp/mu4vogASjvHNpHyyFw0eQqkshN/SWmDvYvoibVND2pJsnHO KYoV/SlmlRqrbUtAR1bKONws8jfCf8g= 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-512-PWjCTELbPCSJ9c_2oec1DA-1; Thu, 15 Apr 2021 12:40:46 -0400 X-MC-Unique: PWjCTELbPCSJ9c_2oec1DA-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 5087319253C0 for ; Thu, 15 Apr 2021 16:40:45 +0000 (UTC) Received: from redhat.com (ovpn-115-159.ams2.redhat.com [10.36.115.159]) by smtp.corp.redhat.com (Postfix) with ESMTPS id CF739694CD; Thu, 15 Apr 2021 16:40:43 +0000 (UTC) Date: Thu, 15 Apr 2021 17:40:40 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Eduardo Habkost Subject: Re: [PATCH RFC] migration: warn about non-migratable configurations unless '--no-migration' was specified Message-ID: References: <20210415154402.28424-1-vkuznets@redhat.com> MIME-Version: 1.0 In-Reply-To: User-Agent: Mutt/2.0.5 (2021-01-21) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=170.10.133.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, 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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Juan Quintela , Markus Armbruster , "Dr . David Alan Gilbert" , "qemu-devel@nongnu.org" , Paolo Bonzini , Vitaly Kuznetsov Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On Thu, Apr 15, 2021 at 12:30:11PM -0400, Eduardo Habkost wrote: > On Thu, Apr 15, 2021 at 12:04 PM Daniel P. Berrangé wrote: > > > > On Thu, Apr 15, 2021 at 05:44:02PM +0200, Vitaly Kuznetsov wrote: > > > When a migration blocker is added nothing is reported to the user, > > > inability to migrate such guest may come as a late surprise. As a bare > > > minimum, we can print a warning. To not pollute the output for those, who > > > have no intention to migrate their guests, introduce '--no-migration' > > > option which both block the migration and eliminates warning from > > > > I wonder how this is actually going to work in practice ? > > > > At the time libvirt starts a guest, it has no idea whether the guest > > is likely to need migration 3, 6, 12, 24 months in to the future. > > I believe the libvirt API could be extended so applications can > indicate that migration is not a required feature. This would let QEMU > automatically enable useful but non-migration-friendly features. For > example, I would expect "-cpu host" to become the default CPU model if > --no-migration is specified. > > > > > IOW, we can't use a --no-migration flag and will be stuck with these > > warnings no mtter what. > > The expected behavior of the libvirt API is to create migratable VMs > by default, isn't it? This means it would be valid for libvirt to use > "--only-migratable" by default. Yes & no. Libvirt attempts to explicitly configure the guest so that it has a stable ABI, and thus can theoretically be migrated We doesn't try to secondguess which QEMU features may or may not be migratable though. > If libvirt can't use "--only-migratable" by default, I would say it's > a deficiency of the libvirt API that needs to be addressed. It is valid to boot a guest with an attached PCI device, which will make it non-migratable, but later hot-unplug the PCI device before starting the migration. > > Is it possible to query the migration blockers via QMP ? > > I don't think it is, but we can add that if it's useful for libvirt. I think it would be useful. > > Libvirt recently introduced a new API 'virDomainGetMessages' which > > lets us report a list of human targetted message strings against > > a guest. We use it for reporting when an operation has tainted > > a guest, and also use it for reporting when a deprecated QEMU > > feature is used. We could use it to report any migration > > blockers that exist. > > > > These are visible from 'virsh dominfo $guestname' and could also > > be displayed by a mgmt application. > > Cool! > > Will the API include all warnings printed by QEMU to stderr? No, we don't look at stderr - that's just going into a logfile. When I refer to deprecated featurs here, I'm talking specifically about stuff we see from the QAPI schema. Right now that means CPU models and machine types with the deprecated flag. It can be extended to other devices later. Regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|