Currently libvirt seems to invoke qemu by "qemu -help" onetime, and then analysis the output text to find whether one type of device the qemu could support. For example, if "qemu -help" prints a text with "-sdl" then libvirt thought the qemu could accept that. But here comes a problem: the output text seems not to adjust its output according to the qemu's compile configuration, so it is possible libvirt invoke qemu with -sdl but get "qemu exit" response that "SDL support is disabled". By default, the sdl is disabled, and the libvirt thought it is on. I wonder if it is a good idea to modify the help function in vl.c, to let it adjust -help output according to the configuration, but this would hide some option of "-help" invocation.
-- Best Regards Wayne Xia mail:xiaw...@linux.vnet.ibm.com tel:86-010-82450803