From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:43791) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1gtEV1-0001z4-BH for qemu-devel@nongnu.org; Mon, 11 Feb 2019 11:32:17 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1gtEUv-0002Zz-Hc for qemu-devel@nongnu.org; Mon, 11 Feb 2019 11:32:02 -0500 Received: from mx1.redhat.com ([209.132.183.28]:57974) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1gtEUu-0002Rx-QP for qemu-devel@nongnu.org; Mon, 11 Feb 2019 11:31:57 -0500 Date: Mon, 11 Feb 2019 16:13:25 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= Message-ID: <20190211161325.GG27585@redhat.com> Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= References: <20190204130958.18904-1-yury-kotov@yandex-team.ru> <20190211160357.GK2627@work-vm> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <20190211160357.GK2627@work-vm> Subject: Re: [Qemu-devel] [PATCH v2 0/5] Add ignore-external migration capability List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Dr. David Alan Gilbert" Cc: Yury Kotov , qemu-devel@lists.ewheeler.net, jiangshanlai@gmail.com, peter.maydell@linaro.org, Laurent Vivier , Thomas Huth , Eduardo Habkost , Peter Crosthwaite , Juan Quintela , qemu-devel@nongnu.org, Markus Armbruster , Paolo Bonzini , Igor Mammedov , wrfsh@yandex-team.ru, Richard Henderson On Mon, Feb 11, 2019 at 04:03:57PM +0000, Dr. David Alan Gilbert wrote: > * Yury Kotov (yury-kotov@yandex-team.ru) wrote: > > Hi, > > > > The series adds a migration capability, which allows to skip shared RAM blocks > > during the migration. It's useful for fast local migration. E.g. to update QEMU > > for the running guests. > > > > Usage example: > > 1. Start source VM: > > qemu-system-x86 \ > > -m 4G \ > > -object memory-backend-file,id=mem0,size=4G,share=on,mem-path=/dev/shm/mem0 \ > > -numa node,memdev=mem0 \ > > -qmp unix:/tmp/qemu-qmp-1.sock,server,nowait \ > > > > 2. Start target VM: > > qemu-system-x86 \ > > -m 4G \ > > -object memory-backend-file,id=mem0,size=4G,share=on,mem-path=/dev/shm/mem0 \ > > -numa node,memdev=mem0 \ > > -qmp unix:/tmp/qemu-qmp-2.sock,server,nowait \ > > -incoming defer > > > > 3. Enable ignore-external capability on both VMs: > > { "execute": "migrate-set-capabilities" , "arguments": > > { "capabilities": [ { "capability": "x-ignore-external", "state": true } ] } } > > > > 4. Start migration. > > > > Another use case I keep in mind is to migrate to file. Usage is very similar. > > Hi, > I've cc'd in Eric, Lai and Peter, all who were asking for something > similar last year; can you all confirm this patch does what you need or > can work with what you needed to do? x-ignore-external is a global setting so affects all memory-backend-file instances. The obvious question is where there is any reasonable/conceivable scenario in which QEMU would have multiple "-object memory-backend-file" intsances and it be neccessary/desirable to migrate some, but skip migrate of others ? Could there ever be a device backend which is using a memory region to communicate with an external process, where you would need to have a new instance for the migration target QEMU, and explicitly not reuse the source QEMU's memory-backend-file storage ? 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 :|