Re: [Qemu-devel] [PATCH 0/3] Allow host_net_add monitor command accept file descriptors

[Avi Kivity]

On 07/06/2009 08:30 PM, Mark McLoughlin wrote:
> Hi,
>         You can pass file descriptors to qemu via the command line using '-net
> tap,fd=' or '-net socket,tap='. However, you cannot currently do this
> via the monitor.
>
>         libvirt always configures tap interfaces before passing them to qemu.
> One reason for this is to allow libvirtd to have privileges
> to /dev/net/tun without allowing qemu those privileges. Because of this,
> libvirt currently does not support NIC hotplug for qemu.
>
>         The following three patches add support for passing a file descriptor
> to the monitor command by allowing file descriptors to be received over
> monitor commands on a unix socket.
>
>    

I'm a great fan of SCM_RIGHTS.  To make it easier to use in more 
commands, I think it makes sense to have a separate command to pass the fd:

  (qemu) getfd foo
  (qemu) getfd bar
  (qemu) getfd baz
  (qemu) pci_add ...,fd=foo
  (qemu) pci_add ...,fd=bar ...,fd=baz

A closefd command would be needed to deal with errors.

--
I have a truly marvellous patch that fixes the bug which this
signature is too narrow to contain.