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 733FDC369A2 for ; Mon, 14 Apr 2025 17:21:12 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1u4NU2-0003sV-Nd; Mon, 14 Apr 2025 13:20:35 -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 1u4NTy-0003rb-Uw for qemu-devel@nongnu.org; Mon, 14 Apr 2025 13:20:31 -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 1u4NTu-0005e0-Mx for qemu-devel@nongnu.org; Mon, 14 Apr 2025 13:20:30 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1744651223; 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=Co5VK7MUg4VE9f5x1YwI4ikKJo7vyYaY24Kbe+QuACQ=; b=awibRmqaAubqznSOJ1P1O9bIr1pAk0lXj+leptTxqi0g2w5V8ohbEr9T7xAWCeX47q98bi kgjeDnXzbAR8TFwQLB6sBlwVoFP13f69Ubaf+2KjSb/ntYM1xE1FDorW3pccFKa/8TB5IS X7olFtEjyVhSVhpiev0qprsp3TJtye8= Received: from mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (ec2-35-165-154-97.us-west-2.compute.amazonaws.com [35.165.154.97]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-523-vf8JrqFhNViyKq4FpHacnA-1; Mon, 14 Apr 2025 13:20:19 -0400 X-MC-Unique: vf8JrqFhNViyKq4FpHacnA-1 X-Mimecast-MFC-AGG-ID: vf8JrqFhNViyKq4FpHacnA_1744651218 Received: from mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.4]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (2048 bits) server-digest SHA256) (No client certificate requested) by mx-prod-mc-06.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 63A45180025A; Mon, 14 Apr 2025 17:20:18 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.99]) by mx-prod-int-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D02BF3001D0F; Mon, 14 Apr 2025 17:20:15 +0000 (UTC) Date: Mon, 14 Apr 2025 18:20:12 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Fabiano Rosas Cc: qemu-devel@nongnu.org, Peter Xu , Markus Armbruster Subject: Re: [RFC PATCH 00/13] migration: Unify capabilities and parameters Message-ID: References: <20250411191443.22565-1-farosas@suse.de> <87v7r6fz0c.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87v7r6fz0c.fsf@suse.de> User-Agent: Mutt/2.2.13 (2024-03-09) X-Scanned-By: MIMEDefang 3.4.1 on 10.30.177.4 Received-SPF: pass client-ip=170.10.129.124; envelope-from=berrange@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_VALIDITY_RPBL_BLOCKED=0.001, RCVD_IN_VALIDITY_SAFE_BLOCKED=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: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org On Mon, Apr 14, 2025 at 02:12:35PM -0300, Fabiano Rosas wrote: > Daniel P. Berrangé writes: > > > On Fri, Apr 11, 2025 at 04:14:30PM -0300, Fabiano Rosas wrote: > >> Open questions: > >> --------------- > >> > >> - Deprecations/compat? > >> > >> I think we should deprecate migrate-set/query-capabilities and everything to do > >> with capabilities (specifically the validation in the JSON at the end of the > >> stream). > >> > >> For migrate-set/query-parameters, we could probably keep it around indefinitely, > >> but it'd be convenient to introduce new commands so we can give them new > >> semantics. > >> > >> - How to restrict the options that should not be set when the migration is in > >> progress? > >> > >> i.e.: > >> all options can be set before migration (initial config) > >> some options can be set during migration (runtime) > >> > >> I thought of adding another type at the top of the hierarchy, with > >> just the options allowed to change at runtime, but that doesn't really > >> stop the others being also set at runtime. I'd need a way to have a > >> set of options that are rejected 'if migration_is_running()', without > >> adding more duplication all around. > >> > >> - What about savevm? > >> > >> None of this solves the issue of random caps/params being set before > >> calling savevm. We still need to special-case savevm and reject > >> everything. Unless we entirely deprecate setting initial options via > >> set-parameters (or set-config) and require all options to be set as > >> savevm (and migrate) arguments. > > > > I'd suggest we aim for a world where the commands take all options > > as direct args and try to remove the global state eventually. > > > > Well, except the options that are adjusted during migration. But yes, I > agree. It all depends on how we proceed with keeping the old commands > around and for how long. If they're still around we can't stop people > from using them and later invoking "savevm" for instance. > > > For savevm/loadvm in particular it is very much a foot-gun that > > 'migrate-set-*' will affect them, because savevm/loadvm aren't > > obviously connected to 'migrate-*' commands unless you're aware > > of how QEMU implements savevm internally. > > > > Yes, I could perhaps reset all options once savevm is called, maybe that > would be acceptable, then we don't need to check and block every single > one. Once we add support to migration options to savevm, then they'd be > set in the savevm command-line from day 1 and those wouldn't be > reset. We could also keep HMP restricted to savevm without any migration > options. That's be easy to enforce. If the user wants fancy savevm, they > can invoke via QMP. Can we make the two approaches mutually exclusive ? Taking your 'migrate' command example addition: { 'command': 'migrate', 'data': {'*uri': 'str', '*channels': [ 'MigrationChannel' ], + '*config': 'MigrationConfig', '*detach': 'bool', '*resume': 'bool' } } if 'migrate' is invoked with the '*config' data being non-nil, then we should ignore *all* global state previously set with migrate-set-XXXX, and exclusively use '*config'. That gives a clean semantic break between old and new approaches, without us having to worry about removing the existing commands quickly. > >> - incoming defer? > >> > >> It seems we cannot do the final step of removing > >> migrate-set-capabilites before we have a form of handshake > >> implemented. That would take the config from qmp_migrate on source and > >> send it to the destination for negotiation. > > > > I'm not sure I understand why the QAPI design changes are tied > > to the new protocol handshake ? I guess you're wanting to avoid > > updating 'migrate_incoming' to accept the new parameters directly ? > > > > Yes, without migrate-set-capabilities, we'd need to pass an enormous > command line to -incoming defer to be able to enable capabilities on the > destination. With the handshake, we could transfer them over the wire > somehow. Does that make sense? '-incoming defer' still gets paired with 'migrate-incoming' on the target, so no matter what, there's no reason to ever pass parameters on the CLI with '-incoming defer'. With 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 :|