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=-17.9 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER,INCLUDES_PATCH,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_1 autolearn=ham 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 AE858C433ED for ; Tue, 4 May 2021 19:18:47 +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 0793D610E9 for ; Tue, 4 May 2021 19:18:46 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 0793D610E9 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]:51978 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1le0ZB-000764-TG for qemu-devel@archiver.kernel.org; Tue, 04 May 2021 15:18:45 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:46832) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1le0Y9-0006TD-M3 for qemu-devel@nongnu.org; Tue, 04 May 2021 15:17:41 -0400 Received: from us-smtp-delivery-124.mimecast.com ([216.205.24.124]:41813) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1le0Y6-0008Mj-A9 for qemu-devel@nongnu.org; Tue, 04 May 2021 15:17:41 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1620155857; 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=/WIo5UxPTlWFpL9ASxYnQPfrwbX1PQacwoJJhX+smtc=; b=SGjfAGuk9bOHMx9IYeLxEQftDf6mrN/mkVuixEQ7L+7UPT5rW7ZDZkco+y5coq20+/N7/T Wem5S3MunofgBPkKlVDxxKAQs+zPUxRLDO4I4fAhmhQ3l8IRrcYNhTvmFcFV5/O6Nj9fVw orrYnW1VltlEEd8zH+5hVMPLjfMJQjo= 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-291-I3jtthmGPjGHk25xCL_CYQ-1; Tue, 04 May 2021 15:17:35 -0400 X-MC-Unique: I3jtthmGPjGHk25xCL_CYQ-1 Received: from smtp.corp.redhat.com (int-mx07.intmail.prod.int.phx2.redhat.com [10.5.11.22]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 47297801817; Tue, 4 May 2021 19:17:34 +0000 (UTC) Received: from work-vm (ovpn-115-50.ams2.redhat.com [10.36.115.50]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 3936310016F8; Tue, 4 May 2021 19:17:33 +0000 (UTC) Date: Tue, 4 May 2021 20:17:30 +0100 From: "Dr. David Alan Gilbert" To: Paolo Bonzini Subject: Re: [PATCH] migration: do not restart VM after successful snapshot-load Message-ID: References: <20210504165826.618801-1-pbonzini@redhat.com> MIME-Version: 1.0 In-Reply-To: <20210504165826.618801-1-pbonzini@redhat.com> User-Agent: Mutt/2.0.6 (2021-03-06) X-Scanned-By: MIMEDefang 2.84 on 10.5.11.22 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=us-ascii Content-Disposition: inline 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: -34 X-Spam_score: -3.5 X-Spam_bar: --- X-Spam_report: (-3.5 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-0.697, 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_H4=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: , Cc: qemu-devel@nongnu.org, qemu-stable@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" * Paolo Bonzini (pbonzini@redhat.com) wrote: > The HMP loadvm code is calling load_snapshot rather than > qmp_snapshot_load, in order to bypass the job infrastructure. The code > around it is almost the same, with one difference: hmp_loadvm is > restarting the VM if load_snapshot fails, qmp_snapshot_load is doing so > if load_snapshot succeeds. > > Fix the bug in QMP by moving the common code to load_snapshot. So I agree it's nice to have them consistent, but hmm. > Cc: qemu-stable@nongnu.org > Signed-off-by: Paolo Bonzini > --- > migration/savevm.c | 16 ++++++++-------- > monitor/hmp-cmds.c | 7 +------ > 2 files changed, 9 insertions(+), 14 deletions(-) > > diff --git a/migration/savevm.c b/migration/savevm.c > index 52e2d72e4b..a899191cbf 100644 > --- a/migration/savevm.c > +++ b/migration/savevm.c > @@ -2992,6 +2992,7 @@ bool load_snapshot(const char *name, const char *vmstate, > int ret; > AioContext *aio_context; > MigrationIncomingState *mis = migration_incoming_get_current(); > + int saved_vm_running = runstate_is_running(); > > if (!bdrv_all_can_snapshot(has_devices, devices, errp)) { > return false; > @@ -3024,6 +3025,8 @@ bool load_snapshot(const char *name, const char *vmstate, > return false; > } > > + vm_stop(RUN_STATE_RESTORE_VM); > + > /* > * Flush the record/replay queue. Now the VM state is going > * to change. Therefore we don't need to preserve its consistency > @@ -3061,13 +3064,17 @@ bool load_snapshot(const char *name, const char *vmstate, > > if (ret < 0) { > error_setg(errp, "Error %d while loading VM state", ret); > - return false; > + goto err_restart; > } I don't think this is safe. If qemu_loadvm_state(f) fails, depending on the point that it fails, the state of the VM is in a part loaded, indeterminate state - it doesn't seem right to auto-restart it. Note, that's a destinct failure from the earlier failures, e.g. trying to find the snapshot and noticing it doesn't exist - that's OK to restart the VM. Then there's the question of what to do if the load_snapshot succeeds; qmp's behaviour of running the loaded-VM doesn't seem wrong to me; although you'd think that would be based on the loaded state not the original; but that's probably a different question. Dave > return true; > > err_drain: > bdrv_drain_all_end(); > +err_restart: > + if (saved_vm_running) { > + vm_start(); > + } > return false; > } > > @@ -3135,17 +3142,10 @@ static void snapshot_load_job_bh(void *opaque) > { > Job *job = opaque; > SnapshotJob *s = container_of(job, SnapshotJob, common); > - int orig_vm_running; > > job_progress_set_remaining(&s->common, 1); > > - orig_vm_running = runstate_is_running(); > - vm_stop(RUN_STATE_RESTORE_VM); > - > s->ret = load_snapshot(s->tag, s->vmstate, true, s->devices, s->errp); > - if (s->ret && orig_vm_running) { > - vm_start(); > - } > > job_progress_update(&s->common, 1); > > diff --git a/monitor/hmp-cmds.c b/monitor/hmp-cmds.c > index 0ad5b77477..a39436c8cb 100644 > --- a/monitor/hmp-cmds.c > +++ b/monitor/hmp-cmds.c > @@ -1127,15 +1127,10 @@ void hmp_balloon(Monitor *mon, const QDict *qdict) > > void hmp_loadvm(Monitor *mon, const QDict *qdict) > { > - int saved_vm_running = runstate_is_running(); > const char *name = qdict_get_str(qdict, "name"); > Error *err = NULL; > > - vm_stop(RUN_STATE_RESTORE_VM); > - > - if (!load_snapshot(name, NULL, false, NULL, &err) && saved_vm_running) { > - vm_start(); > - } > + load_snapshot(name, NULL, false, NULL, &err); > hmp_handle_error(mon, err); > } > > -- > 2.26.2 > -- Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK