Re: [Qemu-devel] "virsh edit" failed to take effect on KVM

[Laszlo Ersek]

On 05/09/13 13:42, Gonglei (Arei) wrote:
> Hi all,
>    we use the command "virsh edit"  to modify the VM configuration 
> information online on KVM Platform(libvirt-1.0.0 and qemu-1.4), 
> but it does not take effect after reboot. However, it works fine on Xen 
> Platform.
>   
>    for an example,a VM is running with the following configuration 
> information:
>          ...
>          <os>
>               <type arch='x86_64'>hvm</type>
>               <boot dev='hd'/>
>               <bootmenu enable='yes'/>
>         </os>
>         ...
>    use command "virsh edit " to modify it:
>          ...
>          <os>
>               <type arch='x86_64'>hvm</type>
>               <boot dev='cdrom'/>
>               <bootmenu enable='yes'/>
>         </os>
>         ...
> With the changing, the VM is expected to start from cdrom, when execute the 
> command "virsh reboot".
> But the fact is that the modify does not take effect, the VM is still start 
> from hd. 
> Well, it will take effect if I use command "virsh shutdown" and "virsh start" 
> instesad of "virsh reboot".
> We are wondering if there have any other ways to take the online modify 
> effect. 
> What is the next step going on with the command "virsh edit" on KVM Platform? 
> Any ideas? 

Under Xen, "xm reboot" (or, more likely, "xl reboot" recently), which is
what I expect "virsh reboot" to translate to, always creates a brand new
domain. Therefore domain config changes take effect.

Under KVM the same VM instance continues to run, it just goes through an
emulated reset.

Laszlo