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=-3.5 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 480BDC4338F for ; Tue, 24 Aug 2021 16:22:56 +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 AD91C61176 for ; Tue, 24 Aug 2021 16:22:55 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.4.1 mail.kernel.org AD91C61176 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=nongnu.org Received: from localhost ([::1]:57294 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mIZCQ-0001L1-EQ for qemu-devel@archiver.kernel.org; Tue, 24 Aug 2021 12:22:54 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:53654) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mIZAc-00086A-RT for qemu-devel@nongnu.org; Tue, 24 Aug 2021 12:21:02 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:30094) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mIZAa-0001i8-GO for qemu-devel@nongnu.org; Tue, 24 Aug 2021 12:21:02 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1629822058; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=EEKe/HgE1zR8POi0NU+cwlTbhnQOB2Ht+zlnlfZxUqM=; b=CgcwzNi3d5WdD7wdgA52aMr1/xYDMPuJF/yKHUkdjJp6x3wtTLVcpCXZugnMpvu3T6yQgN k1HBVC3hI/hWbGX0rKY171h8jRXxS6MX4J5FSvAO73rZFaeVi2EBx/XKUEs58sX5XsjZxQ NxDRR9mWSX0eQg3MZAqsNfjH+CRNgFY= 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-499-d27hHBMhNxWzvYCPbLgxAA-1; Tue, 24 Aug 2021 12:20:55 -0400 X-MC-Unique: d27hHBMhNxWzvYCPbLgxAA-1 Received: from smtp.corp.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.15]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0EEA81853028; Tue, 24 Aug 2021 16:20:54 +0000 (UTC) Received: from redhat.com (unknown [10.39.192.114]) by smtp.corp.redhat.com (Postfix) with ESMTPS id F1C5C5D6CF; Tue, 24 Aug 2021 16:20:52 +0000 (UTC) Date: Tue, 24 Aug 2021 18:20:51 +0200 From: Kevin Wolf To: Peter Maydell Subject: Re: Using loadvm with snapshot Message-ID: References: MIME-Version: 1.0 In-Reply-To: X-Scanned-By: MIMEDefang 2.79 on 10.5.11.15 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=kwolf@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Received-SPF: pass client-ip=216.205.24.124; envelope-from=kwolf@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.747, 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_H2=-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: , Cc: "Dr. David Alan Gilbert" , Gabriel Southern , "qemu-devel@nongnu.org" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" Am 24.08.2021 um 17:25 hat Peter Maydell geschrieben: > On Tue, 24 Aug 2021 at 16:21, Kevin Wolf wrote: > > > > Am 17.08.2021 um 20:48 hat Peter Maydell geschrieben: > > > On Tue, 17 Aug 2021 at 17:27, Dr. David Alan Gilbert > > > wrote: > > > > > > > > * Gabriel Southern (gsouther@qti.qualcomm.com) wrote: > > > > > Hi, > > > > > > > > > > Are there plans to support using -loadvm with -snapshot? > > > > > > > > > > I saw some past discussion on mailing list including bug that was closed earlier this year but no recent activity: > > > > > > > > > > https://lore.kernel.org/qemu-devel/162424905685.11837.7303570061857383641.malone@loganberry.canonical.com/ > > > > > > > > > > Testing with latest qemu it looks like -loadvm still does not work when combined with -snapshot. > > > > > > > > > > I'm curious how complex it would be to implement this feature and if it may show up on QEMU roadmap in the future. Or if there is alterative command that can be used to save the state of a running VM and then use the same qcow to run multiple QEMU instances loading this VM state running in snapshot mode. > > > > > > Do you know why -loadvm and -snapshot don't work together? > > > It doesn't on the face of it seem like they would be incompatible... > > > > Probably because -snapshot first adds a temporary qcow2 overlay to the > > image, and then -loadvm fails because the newly created temporary > > overlay doesn't contain the requested snapshot. > > That sounds like the bug could be fixed by having "find the > snapshot" look not just in the overlay but also down into > the underlying image? In this specific case yes, because we know that the overlay was just created and is still empty. In the general case, loading internal snapshots on a backing file would be wrong because the data in the overlay would be from a different time than the data in the backing file, probably causing data corruption. Kevin