如何动态更换一个虚机CDROM的ISO镜像

Use xm block-list <domid> to find the cdrom be-path for the domain, for example: 

localhost:~# xm block-list 3

Vdev  BE handle state evt-ch ring-ref BE-path

768    0    0     1      -1     -1    /local/domain/0/backend/vbd/3/768  

5632   0    0     1      -1     -1    /local/domain/0/backend/vbd/3/5632 

Having identified the cdrom device (5632) you can check what iso image it is connected to: 

localhost:~# xenstore-read /local/domain/0/backend/vbd/3/5632/params

/root/win/win.ISO

To connect a new iso image: 

xenstore-write local/domain/0/backend/vbd/3/5632/params /mnt/new.iso 

And you can now see that it is connected: 

xenstore-read /local/domain/0/backend/vbd/3/5632/params /mnt/new.iso 

This method works with both emulated devices and with gplpv drivers.