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Thu, 24 Sep 2020 21:50:01 GMT Received: from aserv0121.oracle.com (aserv0121.oracle.com [141.146.126.235]) by aserp3030.oracle.com with ESMTP id 33nujrex1b-1 (version=TLSv1.2 cipher=ECDHE-RSA-AES256-GCM-SHA384 bits=256 verify=OK); Thu, 24 Sep 2020 21:50:01 +0000 Received: from abhmp0008.oracle.com (abhmp0008.oracle.com [141.146.116.14]) by aserv0121.oracle.com (8.14.4/8.13.8) with ESMTP id 08OLo0rs016997; Thu, 24 Sep 2020 21:50:00 GMT Received: from [10.39.244.100] (/10.39.244.100) by default (Oracle Beehive Gateway v4.0) with ESMTP ; Thu, 24 Sep 2020 14:50:00 -0700 Subject: Re: [PATCH V1 05/32] savevm: QMP command for cprload To: "Dr. David Alan Gilbert" References: <1596122076-341293-1-git-send-email-steven.sistare@oracle.com> <1596122076-341293-6-git-send-email-steven.sistare@oracle.com> <654553cb-e071-0498-fe66-78ddda3942e9@redhat.com> <20200911171809.GM3310@work-vm> From: Steven Sistare Organization: Oracle Corporation Message-ID: Date: Thu, 24 Sep 2020 17:49:58 -0400 User-Agent: Mozilla/5.0 (Windows NT 10.0; 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envelope-from=steven.sistare@oracle.com; helo=aserp2130.oracle.com X-detected-operating-system: by eggs.gnu.org: First seen = 2020/09/24 17:43:55 X-ACL-Warn: Detected OS = Linux 3.1-3.10 [fuzzy] X-Spam_score_int: -41 X-Spam_score: -4.2 X-Spam_bar: ---- X-Spam_report: (-4.2 / 5.0 requ) BAYES_00=-1.9, DKIMWL_WL_HIGH=-1.199, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, NICE_REPLY_A=-0.214, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H4=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_PASS=-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: "Daniel P. Berrange" , Juan Quintela , "Michael S. Tsirkin" , qemu-devel@nongnu.org, Markus Armbruster , Alex Williamson , Stefan Hajnoczi , Paolo Bonzini , =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= , =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= , =?UTF-8?Q?Alex_Benn=c3=a9e?= Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 9/11/2020 1:18 PM, Dr. David Alan Gilbert wrote: > * Steven Sistare (steven.sistare@oracle.com) wrote: >> On 7/30/2020 12:14 PM, Eric Blake wrote: >>> On 7/30/20 10:14 AM, Steve Sistare wrote: >>>> Provide the cprload QMP command.  The VM is created from the file produced >>>> by the cprsave command.  Guest RAM is restored in-place from the shared >>>> memory backend file, and guest block devices are used as is.  The contents >>>> of such devices must not be modified between the cprsave and cprload >>>> operations.  If the VM was running at cprsave time, then VM execution >>>> resumes. >>> >>> Is it always wise to unconditionally resume, or might this command need an additional optional knob that says what state (paused or running) to move into? >> >> This can already be done. Issue a stop command before cprsave, then cprload will finish in a >> paused state. >> >> Also, cprsave re-execs and leaves the guest in a paused state. One can >> >> send device add commands, then send cprload which continues >> . > > You're suffering here because you're reinventing stuff rather than > reusing existing migration paths. > With the existing migration code we require the qemu > to be started with -incoming ... so we know it's in a clean > state ready for being loaded, and we've already got the -S > mechanism that dictates whether or not the VM autostarts > (regardless of the saved state in the image). The management > layers find this pretty useful if they need to wire some networking > or storage up at the point they know they've got a VM image that's > loaded OK. I am not seeing the issue here. The manager can hot plug with cprsave as easily as with migration, at the same transition points. I don't see what migration paths should be reused here. CPR Migration - cprsave restarts qemu with the env - qemu -S -incoming defer var QEMU_START_FREEZE set, which clears autostart just like -S. (see patch 15) - command-line devices created - command-line devices created - vmstate is prelaunch - vmstate is inmigrate - manager sends hotplug commands - manager sends hotplug commands - manager sends cprload - manager sends migrate_incoming It would perhaps be more correct for cprsave to leave the vm in the preconfig state. I don't feel like I'm suffering. At least not yet :) - Steve >>>> Syntax: >>>>    {'command':'cprload', 'data':{'file':'str'}} >>>> >>>> Signed-off-by: Steve Sistare >>>> Signed-off-by: Maran Wilson >>>> --- >>> >>>> +++ b/qapi/migration.json >>>> @@ -1635,3 +1635,14 @@ >>>>   ## >>>>   { 'command': 'cprsave', 'data': { 'file': 'str', 'mode': 'str' } } >>>>   +## >>>> +# @cprload: >>>> +# >>>> +# Start virtual machine from checkpoint file that was created earlier using >>>> +# the cprsave command. >>>> +# >>>> +# @file: name of checkpoint file >>>> +# >>>> +# Since 5.0 >>> >>> another 5.2 instance. I'll quit pointing it out for the rest of the series. >> >> Will find and fix all, thanks. >> >> - Steve >>