On Mon, 20 Oct 2025 17:41:30 -0400 Peter Xu <[email protected]> wrote:
> On Wed, Oct 08, 2025 at 05:26:13PM -0400, Peter Xu wrote:
> > On Thu, Sep 04, 2025 at 04:27:39PM +0800, Zhang Chen wrote:
> > > > I confess I didn't test anything on COLO but only from code observations
> > > > and analysis. COLO maintainers: could you add some unit tests to QEMU's
> > > > qtests?
> > >
> > > For the COLO part, I think remove the coroutines related code is OK for
> > > me.
> > > Because the original coroutine still need to call the
> > > "colo_process_incoming_thread".
> >
> > Chen, thanks for the comment. It's still reassuring.
> >
> > >
> > > Hi Hailiang, any comments for this part?
> >
> > Any further comment on this series would always be helpful.
> >
> > It'll be also great if anyone can come up with a selftest for COLO. Now
> > any new migration features needs both unit test and doc to get merged.
> > COLO was merged earlier so it doesn't need to, however these will be
> > helpful for sure to make sure COLO won't be easily broken.
>
> Chen/Hailiang:
>
> I may use some help from COLO side.
>
> Just now, I did give it a shot with the current docs/COLO-FT.txt and it
> didn't really work for me.
>
> The cmdlines I used almost followed the doc, however I changed a few
> things. For example, on secondary VM I added "file.locking=off" for drive
> "parent0" because otherwise the "nbd-server-add" command will fail taking
> the lock and it won't ever boot. Meanwhile I switched to socket netdev
> from tap, in my case I only plan to run the COLO main routine, I hope
> that's harmless too but let me know if it is a problem.
>
> So below are the final cmdlines I used..
>
> For primary:
>
> bin=~/git/qemu/bin/qemu-system-x86_64
> $bin -enable-kvm -cpu qemu64,kvmclock=on \
> -m 512 -smp 1 -qmp stdio \
> -device piix3-usb-uhci -device usb-tablet -name primary \
> -netdev socket,id=hn0,listen=127.0.0.1:10000 \
> -device rtl8139,id=e0,netdev=hn0 \
> -chardev socket,id=mirror0,host=0.0.0.0,port=9003,server=on,wait=off \
> -chardev socket,id=compare1,host=0.0.0.0,port=9004,server=on,wait=on \
> -chardev socket,id=compare0,host=127.0.0.1,port=9001,server=on,wait=off \
> -chardev socket,id=compare0-0,host=127.0.0.1,port=9001 \
> -chardev
> socket,id=compare_out,host=127.0.0.1,port=9005,server=on,wait=off \
> -chardev socket,id=compare_out0,host=127.0.0.1,port=9005 \
> -object filter-mirror,id=m0,netdev=hn0,queue=tx,outdev=mirror0 \
> -object
> filter-redirector,netdev=hn0,id=redire0,queue=rx,indev=compare_out \
> -object filter-redirector,netdev=hn0,id=redire1,queue=rx,outdev=compare0
> \
> -object iothread,id=iothread1 \
> -object
> colo-compare,id=comp0,primary_in=compare0-0,secondary_in=compare1,outdev=compare_out0,iothread=iothread1
> \
> -drive
> if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold=1,children.0.file.filename=./primary.qcow2,children.0.driver=qcow2
>
> For secondary (testing locally, hence using 127.0.0.1 as primary_ip):
>
> bin=~/git/qemu/bin/qemu-system-x86_64
> primary_ip=127.0.0.1
> $bin -enable-kvm -cpu qemu64,kvmclock=on -m 512 -smp 1 -qmp stdio \
> -device piix3-usb-uhci -device usb-tablet -name secondary \
> -netdev socket,id=hn0,connect=127.0.0.1:10000 \
> -device rtl8139,id=e0,netdev=hn0 \
> -chardev socket,id=red0,host=$primary_ip,port=9003,reconnect-ms=1000 \
> -chardev socket,id=red1,host=$primary_ip,port=9004,reconnect-ms=1000 \
> -object filter-redirector,id=f1,netdev=hn0,queue=tx,indev=red0 \
> -object filter-redirector,id=f2,netdev=hn0,queue=rx,outdev=red1 \
> -object filter-rewriter,id=rew0,netdev=hn0,queue=all \
> -drive
> if=none,id=parent0,file.filename=primary.qcow2,driver=qcow2,file.locking=off \
> -drive
> if=none,id=childs0,driver=replication,mode=secondary,file.driver=qcow2,top-id=colo-disk0,file.file.filename=secondary-active.qcow2,file.backing.driver=qcow2,file.backing.file.filename=secondary-hidden.qcow2,file.backing.backing=parent0
> \
> -drive
> if=ide,id=colo-disk0,driver=quorum,read-pattern=fifo,vote-threshold=1,children.0=childs0
> \
> -incoming tcp:0.0.0.0:9998
>
Hi Peter,
You have to use -incoming defer and enable x-colo on the
secondary side before starting migration.
And primary.qcow2 should be a separate image (with same content) for
each qemu instance.
Regards,
Lukas
> I started secondary, then primary, run the suggested QMP commands on
> secondary first, then the bunch of QMP commands on primary. I got below
> error:
>
> x1:colo $ ./primary.sh
> qemu-system-x86_64: -chardev
> socket,id=compare1,host=0.0.0.0,port=9004,server=on,wait=on: info: QEMU
> waiting for connection on: disconnected:tcp:0.0.0.0:9004,server=on
> {"QMP": {"version": {"qemu": {"micro": 50, "minor": 1, "major": 10},
> "package": "v10.1.0-1513-g94586867df"}, "capabilities": ["oob"]}}
> VNC server running on ::1:5900
> {"execute":"qmp_capabilities"}
> {"return": {}}
> {"execute": "human-monitor-command", "arguments": {"command-line": "drive_add
> -n buddy
> driver=replication,mode=primary,file.driver=nbd,file.host=127.0.0.2,file.port=9999,file.export=parent0,node-name=replication0"}}
> {"return": ""}
> {"execute": "x-blockdev-change", "arguments":{"parent": "colo-disk0", "node":
> "replication0" } }
> {"return": {}}
> {"execute": "migrate-set-capabilities", "arguments": {"capabilities": [
> {"capability": "x-colo", "state": true } ] } }
> {"return": {}}
> {"execute": "migrate", "arguments": {"uri": "tcp:127.0.0.2:9998" } }
> {"return": {}}
> {"timestamp": {"seconds": 1760996025, "microseconds": 483349}, "event":
> "STOP"}
>
> x1:colo $ ./secondary.sh
> {"QMP": {"version": {"qemu": {"micro": 50, "minor": 1, "major": 10},
> "package": "v10.1.0-1513-g94586867df"}, "capabilities": ["oob"]}}
> VNC server running on ::1:5901
> {"execute":"qmp_capabilities"}
> {"return": {}}
> {"execute": "migrate-set-capabilities", "arguments": {"capabilities": [
> {"capability": "x-colo", "state": true } ] } }
> {"return": {}}
> {"execute": "nbd-server-start", "arguments": {"addr": {"type": "inet",
> "data": {"host": "0.0.0.0", "port": "9999"} } } }
> {"return": {}}
> {"execute": "nbd-server-add", "arguments": {"device": "parent0", "writable":
> true } }
> {"return": {}}
> {"timestamp": {"seconds": 1760996025, "microseconds": 695059}, "event":
> "RESUME"}
> qemu-system-x86_64: Can't receive COLO message: Input/output error
> {"timestamp": {"seconds": 1760996025, "microseconds": 695369}, "event":
> "COLO_EXIT", "data": {"mode": "secondary", "reason": "error"}}
>
> Do you know what I missed? Or does it mean that COLO is broken?
>
> Meanwhile, do you know if COLO still being used by anyone? I'm pretty sure
> both Fabiano and myself are not looking after it.. I remember Dave used to
> try it, but it might be a long time ago too.
>
> Thanks,
>
pgpkflp5BgJDN.pgp
Description: OpenPGP digital signature
