[libvirt] Supporting vhost-net and macvtap in libvirt for QEMU

Michael S. Tsirkin mst at redhat.com
Sun Dec 20 10:40:48 UTC 2009

On Thu, Dec 17, 2009 at 02:32:32PM -0800, Chris Wright wrote:
> The reason I brought it up here is in case libvirt would be doing both.
> /dev/vhost takes an fd for a tap device or raw socket.  So libvirt would
> need to open both, and then becomes a question of whether libvirt only
> passes the single vhost fd (after setting it up completely) or passes
> both the vhost fd and connecting fd for qemu to put the two together.
> I didn't recall migration (if qemu would need tap fd again).

libvirt should open both fds, pass them to qemu and qemu will
put them together: since vhost might potentially perform direct access
anywhere in guest memory, it would not be safe to let management
control it, so vhost does not let you do it.


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