Re: [Qemu-devel] [RFC PATCH 1/1] ceph/rbd block driver for qemu-kvm

[Christian Brunner <chb@muc.de>]

2010/5/24 MORITA Kazutaka <morita.kazutaka@lab.ntt.co.jp>:

>> However, I don't think nbd would be a good protocol.  My preference
>> would be for a plugin API, or for a new local protocol that uses
>> splice() to avoid copies.
>>
>
> Both would be okay for Sheepdog.  I want to take a suitable approach
> for qemu.

I think both should be possible:

- Using splice() we would need a daemon that is listening on a control
socket for
  requests from qemu-processes or admin commands. When a qemu-process
  wants to open an image it could call open_image("protocol:imagename") on the
  controll socket and the daemon has to create a pipe to which the
image is mapped.
  (What I'm unsure about, are the security implications. Do we need some kind of
  authentication for the sockets? What about sVirt?

- Building a plugin API seems a bit simpler to me, although I'm to
sure if I'd get the
  idea correctly:
  The block layer has already some kind of api (.bdrv_file_open, .bdrv_read). We
  could simply compile the block-drivers as shared objects and create a method
  for loading the necessary modules at runtime.

Are you planing to use this for all block drivers?

Regards,
Christian