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 4C903C3DA45 for ; Thu, 11 Jul 2024 15:45:53 +0000 (UTC) Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1sRvzP-0005Jh-RX; Thu, 11 Jul 2024 11:45:47 -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 1sRvzN-00059t-BU for qemu-devel@nongnu.org; Thu, 11 Jul 2024 11:45:46 -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 1sRvzL-0008Uq-6O for qemu-devel@nongnu.org; Thu, 11 Jul 2024 11:45:44 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1720712742; 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=0jP7HZyWs0t6RVQPfTVJz3wXoufc+TIDSuG/plesnps=; b=T2XjvGeqLVSVvYwrWOEthN439DLcGeZzngPwr+vsrYmuM7EMGLgbN+2g63NYG6c1kckb9K C4LcThjrLtf21OP10J+vu9c6ba8ZPs9INT9GWeB551JadME53w7lXaOGKXh1/fjFJCjSXk s49Qwbcsjl8/v5iAYwDq5jefhg3bKGs= Received: from mx-prod-mc-01.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-355-eW2Ru29kOK-jyVHQXhshAw-1; Thu, 11 Jul 2024 11:45:39 -0400 X-MC-Unique: eW2Ru29kOK-jyVHQXhshAw-1 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-01.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id 630B9196CDF1; Thu, 11 Jul 2024 15:45:37 +0000 (UTC) Received: from redhat.com (unknown [10.42.28.51]) by mx-prod-int-04.mail-002.prod.us-west-2.aws.redhat.com (Postfix) with ESMTPS id D85631956066; Thu, 11 Jul 2024 15:45:34 +0000 (UTC) Date: Thu, 11 Jul 2024 16:45:30 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: "Wang, Wei W" Cc: "pbonzini@redhat.com" , "peterx@redhat.com" , "mtosatti@redhat.com" , "farosas@suse.de" , "qemu-devel@nongnu.org" , "Wang, Lei4" Subject: Re: [PATCH v1] target/i386: kvm: Block migration when enfore_cpuid is set to false Message-ID: References: <20240703144912.130988-1-wei.w.wang@intel.com> 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 10.30.177.40 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: -21 X-Spam_score: -2.2 X-Spam_bar: -- X-Spam_report: (-2.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.142, 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: 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, Jul 11, 2024 at 03:09:28PM +0000, Wang, Wei W wrote: > On Thursday, July 11, 2024 10:14 PM, Daniel P. Berrangé wrote: > > On Thu, Jul 11, 2024 at 02:13:31PM +0000, Wang, Wei W wrote: > > > On Thursday, July 11, 2024 8:25 PM, Daniel P. Berrangé wrote: > > > > On Thu, Jul 11, 2024 at 12:10:34PM +0000, Wang, Wei W wrote: > > > > > On Thursday, July 11, 2024 7:48 PM, Daniel P. Berrangé wrote: > > > > > > On Wed, Jul 03, 2024 at 10:49:12PM +0800, Wei Wang wrote: > > > > > AFAIK, many users are not aware of this, and also we couldn't > > > > > assume everybody knows it. That's why we want to add the enforcement. > > > > > > > > Users who directly launch QEMU are expected to know about QEMU > > > > config details for migration. If they don't, then they ought to be > > > > using a higher level tool like libvirt, which ensures the configuration is > > migration compatible. > > > > > > Agree that libvirt has this advantage and is more user friendly. But > > > it doesn't seem to solve the issue mentioned by this patch - if users don't > > explicitly set "enforce=true" > > > in libvirt configs for the guest, then migrating the guest across > > > hosts with different features could still be risky. Unless there is > > > similar enforcement in libvirt to require users to set "enforce=true" for the > > guest to be migratable. > > > > Yes, libvirt takes steps to ensure CPU compatibility before migrating. > > Thanks for sharing, but curious about those steps. For example, with "enforce=off" > (by default), features on the destination could be filtered by QEMU (kind of silently, > just has warning logs). > How would the source side libvirt get informed about more features getting filtered by > the destination side QEMU (as the destination host has less support for this vcpu model)? > This causes inconsistencies. Libvirt queries QEMU to ask it what features were actually active in the guest. 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 :|