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Date: Thu, 09 May 2013 14:58:56 +0200
From: Laszlo Ersek <lersek@redhat.com>
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Subject: Re: [Qemu-devel] "virsh edit" failed to take effect on KVM
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To: "Gonglei (Arei)" <arei.gonglei@huawei.com>
Cc: Yanqiangjun <yanqiangjun@huawei.com>, Luonengjun <luonengjun@huawei.com>, "qemu-devel@nongnu.org" <qemu-devel@nongnu.org>, "Huangweidong (Hardware)" <huangweidong@huawei.com>

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