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,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 6E845C433E0 for ; Mon, 15 Feb 2021 19:05:05 +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 DC19460C3D for ; Mon, 15 Feb 2021 19:05:04 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org DC19460C3D 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]:59372 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1lBjBA-0006HE-3T for qemu-devel@archiver.kernel.org; Mon, 15 Feb 2021 14:05:04 -0500 Received: from eggs.gnu.org ([2001:470:142:3::10]:54784) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1lBj7r-0003Yf-7s for qemu-devel@nongnu.org; Mon, 15 Feb 2021 14:01:39 -0500 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:56148) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_CBC_SHA1:256) (Exim 4.90_1) (envelope-from ) id 1lBj7n-0003aT-PL for qemu-devel@nongnu.org; Mon, 15 Feb 2021 14:01:38 -0500 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1613415695; 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: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=ageun29/WLwWzAIlZCjc5L+xsxJpPzwcix/hfqXv6Kk=; b=g8mLjtrAP9i8yYHfuOChlCWtwtxzKcHi5xavjvYJhsegnHEkjuUaJ6suw5dG0X43KLleUN uhwmtgW+5Co583izOOU4F74iVK66FOO/pkiF+zPfE0dkLoOOwvYhv5XZ9kJ3vjAO4As76+ byNHZx1rhWzns9r4P8eP0Qf66KXxx44= 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-397-wjLutm-oMlun9SlCXeAesA-1; Mon, 15 Feb 2021 14:01:33 -0500 X-MC-Unique: wjLutm-oMlun9SlCXeAesA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 0CA3B85B66C; Mon, 15 Feb 2021 19:01:32 +0000 (UTC) Received: from work-vm (ovpn-115-61.ams2.redhat.com [10.36.115.61]) by smtp.corp.redhat.com (Postfix) with ESMTPS id D42D95C233; Mon, 15 Feb 2021 19:01:30 +0000 (UTC) Date: Mon, 15 Feb 2021 19:01:28 +0000 From: "Dr. David Alan Gilbert" To: Daniel =?iso-8859-1?Q?P=2E_Berrang=E9?= Subject: Re: [PATCH 00/33] migration: capture error reports into Error object Message-ID: References: <20210204171907.901471-1-berrange@redhat.com> <20210204182249.GO3039@work-vm> <20210204190927.GB903389@redhat.com> <20210208132903.GH3032@work-vm> <20210208134206.GH1141037@redhat.com> <20210215185822.GM1542881@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210215185822.GM1542881@redhat.com> User-Agent: Mutt/2.0.5 (2021-01-21) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 Authentication-Results: relay.mimecast.com; auth=pass smtp.auth=CUSA124A263 smtp.mailfrom=dgilbert@redhat.com X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=iso-8859-1 Content-Disposition: inline Content-Transfer-Encoding: 8bit Received-SPF: pass client-ip=216.205.24.124; envelope-from=dgilbert@redhat.com; helo=us-smtp-delivery-124.mimecast.com X-Spam_score_int: -27 X-Spam_score: -2.8 X-Spam_bar: -- X-Spam_report: (-2.8 / 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_LOW=-0.7, RCVD_IN_MSPIKE_H3=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: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Juan Quintela , Hailiang Zhang , qemu-devel@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Daniel P. Berrangé (berrange@redhat.com) wrote: > On Mon, Feb 15, 2021 at 06:38:05PM +0000, Dr. David Alan Gilbert wrote: > > * Daniel P. Berrangé (berrange@redhat.com) wrote: > > > On Mon, Feb 08, 2021 at 01:29:03PM +0000, Dr. David Alan Gilbert wrote: > > > > * Daniel P. Berrangé (berrange@redhat.com) wrote: > > > > > On Thu, Feb 04, 2021 at 06:22:49PM +0000, Dr. David Alan Gilbert wrote: > > > > > > * Daniel P. Berrangé (berrange@redhat.com) wrote: > > > > > > > Due to its long term heritage most of the migration code just invokes > > > > > > > 'error_report' when problems hit. This was fine for HMP, since the > > > > > > > messages get redirected from stderr, into the HMP console. It is not > > > > > > > OK for QMP because the errors will not be fed back to the QMP client. > > > > > > > > > > > > > > This wasn't a terrible real world problem with QMP so far because > > > > > > > live migration happens in the background, so at least on the target side > > > > > > > there is not a QMP command that needs to capture the incoming migration. > > > > > > > It is a problem on the source side but it doesn't hit frequently as the > > > > > > > source side has fewer failure scenarios. None the less on both sides it > > > > > > > would be desirable if 'query-migrate' can report errors correctly. > > > > > > > With the introduction of the load-snapshot QMP commands, the need for > > > > > > > error reporting becomes more pressing. > > > > > > > > > > > > > > Wiring up good error reporting is a large and difficult job, which > > > > > > > this series does NOT complete. The focus here has been on converting > > > > > > > all methods in savevm.c which have an 'int' return value capable of > > > > > > > reporting errors. This covers most of the infrastructure for controlling > > > > > > > the migration state serialization / protocol. > > > > > > > > > > > > > > The remaining part that is missing error reporting are the callbacks in > > > > > > > the VMStateDescription struct which can return failure codes, but have > > > > > > > no "Error **errp" parameter. Thinking about how this might be dealt with > > > > > > > in future, a big bang conversion is likely non-viable. We'll probably > > > > > > > want to introduce a duplicate set of callbacks with the "Error **errp" > > > > > > > parameter and convert impls in batches, eventually removing the > > > > > > > original callbacks. I don't intend todo that myself in the immediate > > > > > > > future. > > > > > > > > > > > > > > IOW, this patch series probably solves 50% of the problem, but we > > > > > > > still do need the rest to get ideal error reporting. > > > > > > > > > > > > > > In doing this savevm conversion I noticed a bunch of places which > > > > > > > see and then ignore errors. I only fixed one or two of them which > > > > > > > were clearly dubious. Other places in savevm.c where it seemed it > > > > > > > was probably ok to ignore errors, I've left using error_report() > > > > > > > on the basis that those are really warnings. Perhaps they could > > > > > > > be changed to warn_report() instead. > > > > > > > > > > > > > > There are alot of patches here, but I felt it was easier to review > > > > > > > for correctness if I converted 1 function at a time. The series > > > > > > > does not neccessarily have to be reviewed/appied in 1 go. > > > > > > > > > > > > After this series, what do my errors look like, and where do they end > > > > > > up? > > > > > > Do I get my nice backtrace shwoing that device failed, then that was > > > > > > part of that one... > > > > > > > > > > It hasn't modified any of the VMStateDescription callbacks so any > > > > > of the per-device logic that was printing errors will still be using > > > > > error_report to the console as before. > > > > > > > > > > The errors that have changed (at this stage) are only the higher > > > > > level ones that are in the generic part of the code. Where those > > > > > errors mentioned a device name/ID they still do. > > > > > > > > > > In some of the parts I've modified there will have been multiple > > > > > error_reports collapsed into one error_setg() but the ones that > > > > > are eliminated are high level generic messages with no useful > > > > > info, so I don't think loosing those is a problem per-se. > > > > > > > > > > The example that I tested was the case where we load a snapshot > > > > > under a different config that we saved it with. This is the scenario > > > > > that gave the non-deterministic ordering in the iotest you disabled > > > > > from my previous series. > > > > > > > > > > In that case, we changed from: > > > > > > > > > > qemu-system-x86_64: Unknown savevm section or instance '0000:00:02.0/virtio-rng' 0. Make sure that your current VM setup matches your saved VM setup, including any hotplugged devices > > > > > {"return": [{"current-progress": 1, "status": "concluded", "total-progress": 1, "type": "snapshot-load", "id": "load-err-stderr", "error": "Error -22 while loading VM state"}]} > > > > > > > > > > To > > > > > > > > > > {"return": [{"current-progress": 1, "status": "concluded", "total-progress": 1, "type": "snapshot-load", "id": "load-err-stderr", "error": "Unknown savevm section or instance '0000:00:02.0/virtio-rng' 0. Make sure that your current VM setup matches your saved VM setup, including any hotplugged devices"}]} > > > > > > > > > > From a HMP loadvm POV, this means instead of seeing > > > > > > > > > > (hmp) loadvm foo > > > > > Unknown savevm section or instance '0000:00:02.0/virtio-rng' 0. Make sure that your current VM setup matches your saved VM setup, including any hotplugged devices > > > > > Error -22 while loading VM state > > > > > > > > > > You will only see the detailed error message > > > > > > > > > > (hmp) loadvm foo > > > > > Unknown savevm section or instance '0000:00:02.0/virtio-rng' 0. Make sure that your current VM setup matches your saved VM setup, including any hotplugged devices > > > > > > > > > > In this case I think loosing the "Error -22 while loading VM state" > > > > > is fine, as it didn't add value IMHO. > > > > > > > > > > > > > > > If we get around to converting the VMStateDescription callbacks to > > > > > take an error object, then I think we'll possibly need to stack the > > > > > error message from the callback, with the higher level message. > > > > > > > > > > Do you have any familiar/good examples of error message stacking I > > > > > can look at ? I should be able to say whether they would be impacted > > > > > by this series or not - if they are, then I hopefully only threw away > > > > > the fairly useless high level messages, like the "Error -22" message > > > > > above. > > > > > > > > Can you try migrating: > > > > ./x86_64-softmmu/qemu-system-x86_64 -M pc -nographic -device virtio-rng,disable-modern=true > > > > to > > > > ./x86_64-softmmu/qemu-system-x86_64 -M pc -nographic -device virtio-rng > > > > > > > > what I currently get is: > > > > qemu-system-x86_64: get_pci_config_device: Bad config data: i=0x6 read: 0 device: 10 cmask: 10 wmask: 0 w1cmask:0 > > > > qemu-system-x86_64: Failed to load PCIDevice:config > > > > qemu-system-x86_64: Failed to load virtio-rng:virtio > > > > qemu-system-x86_64: error while loading state for instance 0x0 of device '0000:00:04.0/virtio-rng' > > > > qemu-system-x86_64: load of migration failed: Invalid argument > > > > > > After my patches the very last line is gone. > > > > > > So, still reporting using error_report() is the first 3: > > > > > > qemu-system-x86_64: get_pci_config_device: Bad config data: i=0x6 read: 0 device: 10 cmask: 10 wmask: 0 w1cmask:0 > > > qemu-system-x86_64: Failed to load PCIDevice:config > > > qemu-system-x86_64: Failed to load virtio-rng:virtio > > > > > > Then reported in process_incoming_migration_co() using the message > > > populated in the Error object, using error_report_err(): > > > > > > qemu-system-x86_64: error while loading state for instance 0x0 of device '0000:00:04.0/virtio-rng' > > > > > > Finally, this is no longer reported: > > > > > > qemu-system-x86_64: load of migration failed: Invalid argument > > > > > > So in this case we've not lost any useful information > > > > One thing to check, and I *think* you're OK, but we have one place where > > we actually check the error number: > > > > migration.c: > > 3414 static MigThrError migration_detect_error(MigrationState *s) > > ... > > 3426 /* Try to detect any file errors */ > > 3427 ret = qemu_file_get_error_obj(s->to_dst_file, &local_error); > > 3428 if (!ret) { > > 3429 /* Everything is fine */ > > 3430 assert(!local_error); > > 3431 return MIG_THR_ERR_NONE; > > 3432 } > > 3433 > > 3434 if (local_error) { > > 3435 migrate_set_error(s, local_error); > > 3436 error_free(local_error); > > 3437 } > > 3438 > > 3439 if (state == MIGRATION_STATUS_POSTCOPY_ACTIVE && ret == -EIO) { > > 3440 /* > > 3441 * For postcopy, we allow the network to be down for a > > 3442 * while. After that, it can be continued by a > > 3443 * recovery phase. > > 3444 */ > > 3445 return postcopy_pause(s); > > 3446 } else { > > > > This is to go into postcopy pause if the network connection broke (but > > not if for example a device moaned about being in an invalid state) > > > > If I read this correctly, file errors are still being preserved - is > > that correct? > > Yes, in places where QemuFile is reporting an actual I/O error I've > tried to preserve that. Only removed setting of fake I/O errors. So > if anything, we ought to get more accurate at detecting the recoverable > scenarios once we fully cleanup errors. OK, good. Dave > > 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 :| -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK