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