[libvirt] FD passing for chardevs and chardev backend multiplexing

[Paolo Bonzini]

On 09/12/2015 12:19, Daniel P. Berrange wrote:
> > > Now in practice this doesn't work, because qmp_chardev_open_file()
> > > passes the O_CREAT|O_TRUNC flags in, which means the qemu_open()
> > > call will fail when using the pipe FD pased in via fdsets.
> > 
> > Is it just the O_TRUNC that is failing? If so, there is a recent patch
> > to add an 'append':true flag that switches O_TRUNC off in favor of O_APPEND:
> > https://lists.gnu.org/archive/html/qemu-devel/2015-12/msg00762.html
> 
> Yes, it is the ftruncate() call in qemu_dup_flags, called from qemu_open
> that is failing.

It will require a little auditing, but I think ignoring EINVAL from that
fruncate() is fine.

Paolo