On 09/15/2009 04:50 PM, Gregory Haskins wrote:

quoted

Why?  vhost will call get_user_pages() or copy_*_user() which ought to
do the right thing.
     

I was speaking generally, not specifically to Ira's architecture.  What
I mean is that vbus was designed to work without assuming that the
memory is pageable.  There are environments in which the host is not
capable of mapping hvas/*page, but the memctx->copy_to/copy_from
paradigm could still work (think rdma, for instance).
   

Sure, vbus is more flexible here.

quoted

quoted

As an aside: a bigger issue is that, iiuc, Ira wants more than a single
ethernet channel in his design (multiple ethernets, consoles, etc).  A
vhost solution in this environment is incomplete.

       

Why?  Instantiate as many vhost-nets as needed.
     

a) what about non-ethernets?
   

There's virtio-console, virtio-blk etc.  None of these have kernel-mode 
servers, but these could be implemented if/when needed.

b) what do you suppose this protocol to aggregate the connections would
look like? (hint: this is what a vbus-connector does).
   

You mean multilink?  You expose the device as a multiqueue.

c) how do you manage the configuration, especially on a per-board basis?
   

pci (for kvm/x86).

Actually I have patches queued to allow vbus to be managed via ioctls as
well, per your feedback (and it solves the permissions/lifetime
critisims in alacrityvm-v0.1).
   

That will make qemu integration easier.

quoted

  The only difference is the implementation.  vhost-net
leaves much more to userspace, that's the main difference.
     

Also,

*) vhost is virtio-net specific, whereas vbus is a more generic device
model where thing like virtio-net or venet ride on top.
   

I think vhost-net is separated into vhost and vhost-net.

*) vhost is only designed to work with environments that look very
similar to a KVM guest (slot/hva translatable).  vbus can bridge various
environments by abstracting the key components (such as memory access).
   

Yes.  virtio is really virtualization oriented.

*) vhost requires an active userspace management daemon, whereas vbus
can be driven by transient components, like scripts (ala udev)
   

vhost by design leaves configuration and handshaking to userspace.  I 
see it as an advantage.

-- 
error compiling committee.c: too many arguments to function

--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org.  For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>