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 2E3A2D4337D for ; Thu, 7 Nov 2024 16:58:24 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1t95pj-0005w3-3C; Thu, 07 Nov 2024 11:58:11 -0500 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 1t95pc-0005vB-Rz for qemu-devel@nongnu.org; Thu, 07 Nov 2024 11:58:04 -0500 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 1t95pa-0008CL-Qg for qemu-devel@nongnu.org; Thu, 07 Nov 2024 11:58:04 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1730998680; 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=hD8D7pc1VOi/5QPPAdQs9Amy9e/NF6C0aPHm50kUvPQ=; b=KW8B0fxAdsyKNzNRo3+1q6EXRPezRDnDVI5R/1qkuO/qRyM5Gyb58NRDHKvT4zctOafdEj hFUQ0WC0RSl78v0UHK6fxdQ17QeD+gQ2WWAbIeg6Lb/5ni3qiwdp5Q0FZQ9sRNjYpOJezY /8dxIVAbtTQkkYyRo/EojX+QHJ7+Za0= Received: from mx-prod-mc-03.mail-002.prod.us-west-2.aws.redhat.com (ec2-54-186-198-63.us-west-2.compute.amazonaws.com [54.186.198.63]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.3, cipher=TLS_AES_256_GCM_SHA384) id us-mta-690-UL3YAcy7MiSjZkmXsEAytQ-1; Thu, 07 Nov 2024 11:57:59 -0500 X-MC-Unique: UL3YAcy7MiSjZkmXsEAytQ-1 X-Mimecast-MFC-AGG-ID: UL3YAcy7MiSjZkmXsEAytQ Received: from mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com [10.30.177.12]) (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-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 7BFF81956057; Thu, 7 Nov 2024 16:57:57 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.55]) by mx-prod-int-03.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 882B6195E480; Thu, 7 Nov 2024 16:57:50 +0000 (UTC) Date: Thu, 7 Nov 2024 16:57:46 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Peter Xu Cc: Prasad Pandit , Fabiano Rosas , qemu-devel@nongnu.org, Prasad Pandit Subject: Re: [PATCH 2/5] migration/postcopy: magic value for postcopy channel Message-ID: References: <87ldxw1p8k.fsf@suse.de> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: User-Agent: Mutt/2.2.12 (2023-09-09) X-Scanned-By: MIMEDefang 3.0 on 10.30.177.12 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: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.34, 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_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, RCVD_IN_VALIDITY_CERTIFIED_BLOCKED=0.001, RCVD_IN_VALIDITY_RPBL_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 Thu, Nov 07, 2024 at 11:17:30AM -0500, Peter Xu wrote: > On Thu, Nov 07, 2024 at 12:33:17PM +0000, Daniel P. Berrangé wrote: > I'll comment on a few examples above, which I think some of them, even if > handshake is ready, may still need mgmt layers to involve.. > > Multifd and postcopy are the two major features, and they, IMHO, all better > need user involvements.. > > Multifd needs it because it relies on the channel being able to provide >1 > channels. It means "| nc XXX > file" can stop working if we turn it on by > default silently. NB, my point was referring to a hypothetical alternative history, where we had the handshake at the QEMU level from day 1. That would neccessarily imply a bi-directional channel, so the 'nc' use case would already have been out of scope. That said, QEMU could identify whether the channel it was told to use was bi-directional or not, and thus not try to do multifd over a non-socket transport. So the general point still holds - if QEMU had this protocol negotiation phase built-in, there would be more flexiblity in introducing new features without layers above needing changes, for every single one, just a subset. 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 :|