Hi Michael,
I'll reserve individual patch review until they're in a mergable state,
but I do have some comments about the overall integration architecture.
Generally speaking, I think the integration unnecessarily invasive. It
adds things to the virtio infrastructure that shouldn't be there like
the irqfd/queuefd bindings. It also sneaks in things like raw backend
support which really isn't needed.
I think we can do better. Here's what I suggest:
The long term goal should be to have a NetDevice interface that looks
very much like virtio-net but as an API, not an ABI. Roughly, it would
look something like:
struct NetDevice {
int add_xmit(NetDevice *dev, struct iovec *iov, int iovcnt, void *token);
int add recv(NetDevice *dev, struct iovec *iov, int iovcnt, void *token);
void *get_xmit(NetDevice *dev);
void *get_recv(NetDevice *dev);
void kick(NetDevice *dev);
...
};
That gives us a better API for use with virtio-net, e1000, etc.
Assuming we had this interface, I think a natural extension would be:
int add_ring(NetDevice *dev, void *address);
int add_kickfd(NetDevice *dev, int fd);
For slot management, it really should happen outside of the NetDevice
structure. We'll need a slot notifier mechanism such that we can keep
this up to date as things change.
vhost-net because a NetDevice. It can support things like the e1000 by
doing ring translation behind the scenes. virtio-net can be fast pathed
in the case that we're using KVM but otherwise, it would also rely on
the ring translation. N.B. in the case vhost-net is fast pathed, it
requires a different device in QEMU that uses a separate virtio
transport. We should reuse as much code as possible obviously. It
doesn't make sense to have all of the virtio-pci code and virtio-net
code in place when we aren't using it.
All this said, I'm *not* suggesting you have to implement all of this to
get vhost-net merged. Rather, I'm suggesting that we should try to
structure the current vhost-net implementation to complement this
architecture assuming we all agree this is the sane thing to do. That
means I would make the following changes to your series:
- move vhost-net support to a VLANClientState backend.
- do not introduce a raw socket backend
- if for some reason you want to back to tap and raw, those should be
options to the vhost-net backend.
- when fast pathing with vhost-net, we should introduce interfaces to
VLANClientState similar to add_ring and add_kickfd. They'll be very
specific to vhost-net for now, but that's okay.
- sort out the layering of vhost-net within the virtio infrastructure.
vhost-net should really be it's own qdev device. I don't see very much
code reuse happening right now so I don't understand why it's not that
way currently.
Regards,
Anthony Liguori
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