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

[Dr. David Alan Gilbert]

* Peter Lieven (address@hidden) wrote:
> Am 07.04.2015 um 17:29 schrieb Dr. David Alan Gilbert:
> > * Peter Lieven (address@hidden) 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
    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.

Dave

> 
> Peter
--
Dr. David Alan Gilbert / address@hidden / Manchester, UK