[Users] Migration issues with ovirt 3.3

[Dan Kenigsberg]

On Mon, Oct 07, 2013 at 12:25:30AM +0200, Gianluca Cecchi wrote:
> I've done some further tests and comparisons

Is this related to emitor's bug? For emitor, when a VM does not start it
happens when libvirt recongnizes that its devices have bad addresses. It
never gets to qemu command line phase.

> 
> In this F19 based + ovirt stable repo the difference in qemu command
> line between the working run once with cd enabled of this CentOS 6.4
> x86_64 and the normal run that doesn't proceed is:
> 
> run once
> -drive file=/rhev/data-center/mnt/f18engine.mydomain:_var_lib_exports_iso/cc790a86-72e2-4aa2-a0b6-700756c399c3/images/11111111-1111-1111-1111-111111111111/CentOS-6.4-x86_64-bin-DVD1.iso,if=none,id=drive-ide0-1-0,readonly=on,format=raw,serial=
> -device ide-cd,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0,bootindex=2
> 
> run
> -drive if=none,id=drive-ide0-1-0,readonly=on,format=raw,serial=
> -device ide-cd,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0
> 
> 
> A working normal run of a WinXP 32bit VM in another oVirt 3.2.3 environment is
> -drive if=none,id=drive-ide0-1-0,readonly=on,format=raw,serial=
> -device ide-cd,bus=ide.1,unit=0,drive=drive-ide0-1-0,id=ide0-1-0
> 
> so it is the same as in 3.3.
> 
> Possible problems:
> 
> - 64bit OS
> I can try tomorrow to create a CentOS 6.4 32 bit and compare results
> 
> - qemu default emulated pc version
> 
> Some comparisons
> 
> a) f18 host (AIO) with oVirt 3.2.3
> 
> qemu-kvm-1.2.2-14.fc18.x86_64
> 
> [root at tekkaman polimi]# qemu-kvm -machine ?
> Supported machines are:
> none                 empty machine
> pc                   Standard PC (alias of pc-1.2)
> pc-1.2               Standard PC (default)
> pc-1.1               Standard PC
> pc-1.0               Standard PC
> pc-0.15              Standard PC
> pc-0.14              Standard PC
> pc-0.13              Standard PC
> pc-0.12              Standard PC
> pc-0.11              Standard PC, qemu 0.11
> pc-0.10              Standard PC, qemu 0.10
> isapc                ISA-only PC
> 
> When I start WinXP (32bit of course) I see this command line:
> /usr/bin/qemu-kvm -name winxp -S -M pc-0.14 -cpu Opteron_G3 ....
> 
> b) f19 host in oVirt 3.3
> 
> qemu-kvm-1.4.2-11.fc19.x86_64
> 
> [root at f18ovn03 ~]# qemu-kvm -machine ?
> Supported machines are:
> none                 empty machine
> pc                   Standard PC (i440FX + PIIX, 1996) (alias of pc-i440fx-1.4)
> pc-i440fx-1.4        Standard PC (i440FX + PIIX, 1996) (default)
> pc-1.3               Standard PC
> pc-1.2               Standard PC
> pc-1.1               Standard PC
> pc-1.0               Standard PC
> pc-0.15              Standard PC
> pc-0.14              Standard PC
> pc-0.13              Standard PC
> pc-0.12              Standard PC
> pc-0.11              Standard PC, qemu 0.11
> pc-0.10              Standard PC, qemu 0.10
> isapc                ISA-only PC
> q35                  Standard PC (Q35 + ICH9, 2009) (alias of pc-q35-1.4)
> pc-q35-1.4           Standard PC (Q35 + ICH9, 2009)
> 
> qemu command line for a CentOS 6.4 64bit vm is:
> /usr/bin/qemu-system-x86_64 -machine accel=kvm -name c6s -S -machine
> pc-1.0,accel=kvm,usb=off -cpu Opteron_G2
> 
> both /usr/bin/qemu-kvm and /usr/bin/qemu-system-x86_64 are in
> qemu-system-x86 rpm package.
> 
> Questions:
> - given a version of oVirt, pc version in qemu generated command line
> is the same for every defined VM or is there any logic depending on OS
> chosen and/or bit (32 vs 64)?
emulatedMachine is set by the effective clusterLevel.

> - if answer to previous question is fixed pc version, is there any
> particular reason to use pc-0.14 in oVirt 3.2.3 and pc-1.0 in oVirt
> 3.3 and not the latest available (so pc-1.2 in 3.2.3 and pc-1.3 or
> pc-i440fx-1.4 in 3.3)?

We promise inter-cluster migration of VMs. Hence, 3.2.3 may use only the
newest machine available at 3.2.0.

> - where can I find documentation about difference between the
> different pc-x.y versions?

I am not aware of anything beyond the qemu source code and release
notes.

> - can I use a wrapper in oVirt 3.3 to start VM with a different pc-x.y
> (eg pc-0.14) and see if anything changes helping debug and solve the
> problem?

Yes, you may write a vdsm before_vm_start hook. It should search for
the 'machine' attribute and set it to whatever value you please.

Dan.