Re: [libvirt] [PATCH v2] Add support for fd: protocol

On 06/14/2011 07:31 AM, Corey Bryant wrote: > > - Starting Qemu with a backing file What do you mean by this? Taking a guess: In the case of a qcow2 image with a backing file, does that mean that both the qcow2 image and it's backing file can both be passed to qemu via fd: notations? That is, if the -drive file=fd:4,format=qcow2 option is passed, and fd4 is a qcow2 image that also has a backing file, it seems like libvirt should also be able to pass that backing file via another fd, so that qemu doesn't have to open() the backing file directly. So we would need something like -drive file=fd:4,format=qcow2,backing=fd:5 and since backing files can be nested, we'd need some way of specifying more than one level of backing file. Libvirt already knows how to walk a chain of backing images in qcow2 files (it has to, in order to set sVirt SELinux permissions on all of those files so that qemu can open() each file), so it wouldn't be much harder for libvirt to instead do the open() and pass each fd. -- Eric Blake eblake(a)redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org