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=-5.1 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED,USER_AGENT_SANE_1 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 65B35C433E7 for ; Thu, 15 Oct 2020 11:47:38 +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 8DFFC20BED for ; Thu, 15 Oct 2020 11:47:37 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="KawJBla1" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8DFFC20BED Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:48786 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1kT1jM-0001Zy-IC for qemu-devel@archiver.kernel.org; Thu, 15 Oct 2020 07:47:36 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:52714) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1kT1iU-0000p1-MM for qemu-devel@nongnu.org; Thu, 15 Oct 2020 07:46:43 -0400 Received: from us-smtp-delivery-124.mimecast.com ([63.128.21.124]:51059) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1kT1iS-0002f5-PT for qemu-devel@nongnu.org; Thu, 15 Oct 2020 07:46:42 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1602762399; 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=V9WX+yv1+WD0V4aye6W7SJEE1GZCq7/F6yqDF9/y7f8=; b=KawJBla1hQN4OhuDi8hYzqWTxw+7Zjfekgc8RlEv0JJFdb/4Op0OgSAjJPv+qVVh51cmdH 5BWZLNsnagdGFFsxGqLmV0swbXQFIUtg6l7tYxQjoFb99u6sbFEyIZiuSs4VFp+gQvjAhR 6+rAeibjDd1fhc/jJOhlKTFpxqiEUPs= 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-208-pndmA-NLNi29Niw0gbsa9A-1; Thu, 15 Oct 2020 07:46:29 -0400 X-MC-Unique: pndmA-NLNi29Niw0gbsa9A-1 Received: from smtp.corp.redhat.com (int-mx01.intmail.prod.int.phx2.redhat.com [10.5.11.11]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 8B075803620; Thu, 15 Oct 2020 11:46:28 +0000 (UTC) Received: from redhat.com (ovpn-114-115.ams2.redhat.com [10.36.114.115]) by smtp.corp.redhat.com (Postfix) with ESMTPS id BA35D76669; Thu, 15 Oct 2020 11:46:25 +0000 (UTC) Date: Thu, 15 Oct 2020 12:46:22 +0100 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: qemu-devel@nongnu.org Subject: Re: [PATCH v6 00/10] migration: bring improved savevm/loadvm/delvm to QMP Message-ID: <20201015114622.GF163620@redhat.com> References: <20201008155001.3357288-1-berrange@redhat.com> MIME-Version: 1.0 In-Reply-To: <20201008155001.3357288-1-berrange@redhat.com> User-Agent: Mutt/1.14.6 (2020-07-11) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.11 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=berrange@redhat.com X-Mimecast-Spam-Score: 0.003 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Content-Disposition: inline Received-SPF: pass client-ip=63.128.21.124; envelope-from=berrange@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/10/15 02:10:02 X-ACL-Warn: Detected OS = Linux 2.2.x-3.x [generic] [fuzzy] 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, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=unavailable 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Cc: Kevin Wolf , Peter Krempa , "Denis V. Lunev" , qemu-block@nongnu.org, Juan Quintela , John Snow , Markus Armbruster , Max Reitz , Pavel Dovgalyuk , Paolo Bonzini , "Dr. David Alan Gilbert" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" ping: for anyone in the block or migration maintainers teams to review this, since Markus has acked the QAPI design side of it. On Thu, Oct 08, 2020 at 04:49:51PM +0100, Daniel P. Berrangé wrote: > v1: https://lists.gnu.org/archive/html/qemu-devel/2020-07/msg00866.html > v2: https://lists.gnu.org/archive/html/qemu-devel/2020-07/msg07523.html > v3: https://lists.gnu.org/archive/html/qemu-devel/2020-08/msg07076.html > v4: https://lists.gnu.org/archive/html/qemu-devel/2020-09/msg05221.html > v5: https://lists.gnu.org/archive/html/qemu-devel/2020-10/msg00587.html > > This series aims to provide a better designed replacement for the > savevm/loadvm/delvm HMP commands, which despite their flaws continue > to be actively used in the QMP world via the HMP command passthrough > facility. > > The main problems addressed are: > > - The logic to pick which disk to store the vmstate in is not > satsifactory. > > The first block driver state cannot be assumed to be the root disk > image, it might be OVMF varstore and we don't want to store vmstate > in there. > > - The logic to decide which disks must be snapshotted is hardwired > to all disks which are writable > > Again with OVMF there might be a writable varstore, but this can be > raw rather than qcow2 format, and thus unable to be snapshotted. > While users might wish to snapshot their varstore, in some/many/most > cases it is entirely uneccessary. Users are blocked from snapshotting > their VM though due to this varstore. > > - The commands are synchronous blocking execution and returning > errors immediately. > > This is partially addressed by integrating with the job framework. > This forces the client to use the async commands to determine > the completion status or error message from the operations. > > In the block code I've only dealt with node names for block devices, as > IIUC, this is all that libvirt should need in the -blockdev world it now > lives in. IOW, I've made not attempt to cope with people wanting to use > these QMP commands in combination with -drive args, as libvirt will > never use -drive with a QEMU new enough to have these new commands. > > The main limitations of this current impl > > - The snapshot process runs serialized in the main thread. ie QEMU > guest execution is blocked for the duration. The job framework > lets us fix this in future without changing the QMP semantics > exposed to the apps. > > - Most vmstate loading errors just go to stderr, as they are not > using Error **errp reporting. Thus the job framework just > reports a fairly generic message > > "Error -22 while loading VM state" > > Again this can be fixed later without changing the QMP semantics > exposed to apps. > > I've done some minimal work in libvirt to start to make use of the new > commands to validate their functionality, but this isn't finished yet. > > My ultimate goal is to make the GNOME Boxes maintainer happy again by > having internal snapshots work with OVMF: > > https://gitlab.gnome.org/GNOME/gnome-boxes/-/commit/c486da262f6566326fbcb5e= > f45c5f64048f16a6e > > Changed in v6: > > - Resolve many conflicts with recent replay changes > - Misc typos in QAPI > > Changed in v5: > > - Fix prevention of tag overwriting > - Refactor and expand test suite coverage to validate > more negative scenarios > > Changed in v4: > > - Make the device lists mandatory, dropping all support for > QEMU's built-in heuristics to select devices. > > - Improve some error reporting and I/O test coverage > > Changed in v3: > > - Schedule a bottom half to escape from coroutine context in > the jobs. This is needed because the locking in the snapshot > code goes horribly wrong when run from a background coroutine > instead of the main event thread. > > - Re-factor way we iterate over devices, so that we correctly > report non-existant devices passed by the user over QMP. > > - Add QAPI docs notes about limitations wrt vmstate error > reporting (it all goes to stderr not an Error **errp) > so QMP only gets a fairly generic error message currently. > > - Add I/O test to validate many usage scenarios / errors > > - Add I/O test helpers to handle QMP events with a deterministic > ordering > > - Ensure 'delete-snapshot' reports an error if requesting > delete from devices that don't support snapshot, instead of > silently succeeding with no erro. > > Changed in v2: > > - Use new command names "snapshot-{load,save,delete}" to make it > clear that these are different from the "savevm|loadvm|delvm" > as they use the Job framework > > - Use an include list for block devs, not an exclude list > > Daniel P. Berrang=C3=A9 (10): > block: push error reporting into bdrv_all_*_snapshot functions > migration: stop returning errno from load_snapshot() > block: add ability to specify list of blockdevs during snapshot > block: allow specifying name of block device for vmstate storage > block: rename and alter bdrv_all_find_snapshot semantics > migration: control whether snapshots are ovewritten > migration: wire up support for snapshot device selection > migration: introduce a delete_snapshot wrapper > iotests: add support for capturing and matching QMP events > migration: introduce snapshot-{save,load,delete} QMP commands > > block/monitor/block-hmp-cmds.c | 7 +- > block/snapshot.c | 256 +++++++++++++++------ > include/block/snapshot.h | 23 +- > include/migration/snapshot.h | 14 +- > migration/savevm.c | 280 ++++++++++++++++++++--- > monitor/hmp-cmds.c | 12 +- > qapi/job.json | 9 +- > qapi/migration.json | 121 ++++++++++ > replay/replay-debugging.c | 12 +- > replay/replay-snapshot.c | 5 +- > softmmu/vl.c | 2 +- > tests/qemu-iotests/267.out | 12 +- > tests/qemu-iotests/310 | 385 +++++++++++++++++++++++++++++++ > tests/qemu-iotests/310.out | 407 +++++++++++++++++++++++++++++++++ > tests/qemu-iotests/common.qemu | 107 ++++++++- > tests/qemu-iotests/group | 1 + > 16 files changed, 1508 insertions(+), 145 deletions(-) > create mode 100755 tests/qemu-iotests/310 > create mode 100644 tests/qemu-iotests/310.out > > --=20 > 2.26.2 > 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 :|