Re: [Qemu-devel] [Qemu-block] Migration sometimes fails with IDE and Qemu 2.2.1

[Peter Lieven <pl@kamp.de>]

Am 07.04.2015 um 21:01 schrieb Dr. David Alan Gilbert:
> * Peter Lieven (pl@kamp.de) wrote:
>> Am 07.04.2015 um 17:29 schrieb Dr. David Alan Gilbert:
>>> * Peter Lieven (pl@kamp.de) wrote:
>>>> Hi David,
>>>>
>>>> Am 07.04.2015 um 10:43 schrieb Dr. David Alan Gilbert:
>>>>>>>> Any particular workload or reproducer?
>>>>>>> Workload is almost zero. I try to figure out if there is a way to trigger it.
>>>>>>>
>>>>>>> Maybe playing a role: Machine type is -M pc1.2 and we set -kvmclock as
>>>>>>> CPU flag since kvmclock seemed to be quite buggy in 2.6.16...
>>>>>>>
>>>>>>> Exact cmdline is:
>>>>>>> /usr/bin/qemu-2.2.1  -enable-kvm  -M pc-1.2  -nodefaults -netdev type=tap,id=guest2,script=no,downscript=no,ifname=tap2  -device e1000,netdev=guest2,mac=52:54:00:ff:00:65 -drive format=raw,file=iscsi://172.21.200.53/iqn.2001-05.com.equallogic:4-52aed6-88a7e99a4-d9e00040fdc509a3-XXX-hd0/0,if=ide,cache=writeback,aio=native  -serial null  -parallel null  -m 1024 -smp 2,sockets=1,cores=2,threads=1  -monitor tcp:0:4003,server,nowait -vnc :3 -qmp tcp:0:3003,server,nowait -name 'XXX' -boot order=c,once=dc,menu=off  -drive index=2,media=cdrom,if=ide,cache=unsafe,aio=native,readonly=on  -k de  -incoming tcp:0:5003  -pidfile /var/run/qemu/vm-146.pid  -mem-path /hugepages  -mem-prealloc  -rtc base=utc -usb -usbdevice tablet -no-hpet -vga cirrus  -cpu qemu64,-kvmclock
>>>>>>>
>>>>>>> Exact kernel is:
>>>>>>> 2.6.16.46-0.12-smp (i think this is SLES10 or sth.)
>>>>>>>
>>>>>>> The machine does not hang. It seems just I/O is hanging. So you can type at the console or ping the system, but no longer login.
>>>>>>>
>>>>>>> Thank you,
>>>>>>> Peter
>>>>>> Interesting observation: Migrating the vServer again seems to fix to problem (at least in one case I could test just now).
>>>>>>
>>>>>> 2.6.8-24-smp is also affected.
>>>>> How often does it fail - you say 'sometimes' - is it a 1/10 or a 1/1000 ?
>>>> Its more often than 1/10 I would say.
>>> OK, that's not too bad - it's the 1/1000 that are really nasty to find.
>>> In your setup, how easy would it be for you to try :
>>>     with either 2.1 or current head?
>>>     with a newer machine-type?
>>>     without the cdrom?
>> Its all possible. I can clone the system and try everything on my test systems. I hope
>> it reproduces there.
> Great.  I think the order I would go would be:
>     Try head - if it works we know we've already got the fix somewhere
>     Try 2.1  - if it works we know it's something we introduced between
>                2.1 and 2.2.1
>     Try a newer machine type - because pc-1.2 probably isn't tested much

I don't mind chaning the machine time. The reason it is pc-1.2 is we
set the machine type the vServer was created with.

>     CDROM at the end.
>
>> Has the cdrom the power of taking down the bus?
> I just know the cdrom migration is a bit lacking and the simpler
> the test case the better.

Just for the record there was no CD inserted during migration.

Peter