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

[Peter Lieven]

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.

>
> I'm not sure at what kernel version the switch is, but newer kernels use some
> code shared with the newer SATA world (libata?)  where as older kernels had
> separate IDE code, so the behaviour of the two can be quite different.

Thats a good point. I will check what the kernels have.
I remember that there was sth like a problem with error handling in
the old drivers? Paolo, you worked a lot on IDE lately. Do you remember?

Thanks,
Peter