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 D927AC369A2 for ; Mon, 14 Apr 2025 19:07:47 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1u4P8s-0006kg-5g; Mon, 14 Apr 2025 15:06:50 -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 1u4P8n-0006jd-VI for qemu-devel@nongnu.org; Mon, 14 Apr 2025 15:06:46 -0400 Received: from us-smtp-delivery-124.mimecast.com ([170.10.133.124]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1u4P8l-0001Mz-I5 for qemu-devel@nongnu.org; Mon, 14 Apr 2025 15:06:45 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1744657601; 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=lFVGNK6PC5etabM/CPSVbyT5/vC3txZXLKiRBb0gmvQ=; b=UbASHOZ+xmXOivH+XCNfrQEvmvbz8Qg0qcC1/bo4hPrZzFj/kLMzr2AXxm6SGr5Er1Sh9N l9VPlA94aNpLlu145Eq/MovIg/Dya5gpCHBKLj/f4f3CByIa1RksJtq4TUMU+X/TsMUEPt Uc6+zT6R65/jH16aQ6vc7HxcdYc6CL4= Received: from mx-prod-mc-08.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-226-o3txNScePcOEQuhoUiE1PA-1; Mon, 14 Apr 2025 15:06:37 -0400 X-MC-Unique: o3txNScePcOEQuhoUiE1PA-1 X-Mimecast-MFC-AGG-ID: o3txNScePcOEQuhoUiE1PA_1744657594 Received: from mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.40]) (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-08.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 83638180AF55; Mon, 14 Apr 2025 19:06:34 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.99]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 77A821955BF2; Mon, 14 Apr 2025 19:06:32 +0000 (UTC) Date: Mon, 14 Apr 2025 20:06:29 +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> <87semafxpy.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <87semafxpy.fsf@suse.de> User-Agent: Mutt/2.2.13 (2024-03-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.40 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: -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_H5=0.001, RCVD_IN_MSPIKE_WL=0.001, 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 02:40:25PM -0300, Fabiano Rosas wrote: > Daniel P. Berrangé writes: > > > 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. > > > > Good idea. I will need to do something about the -global options because > they also set the defaults for the various options. But we should be > able to decouple setting defaults from -global. Or I could just apply > -global again on top of what came in '*config'. > > > > >> >> - 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'. > > > > Oops, I misread the strcmp in vl.c. I mean -incoming uri is the one > that'll need a huge cmdline. > > But if we follow your suggestion above we could just tie -incoming URI > to the existing commands and make the new format require defer. Yes, modern approach should require '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 :|