Hi Asias,
Looks nice! Some comments inline below (I've removed anything that mst already
commented on).
On 06/27/2013 03:59 AM, Asias He wrote:
Hello guys,
In commit d021c344051af91 (VSOCK: Introduce VM Sockets), VMware added VM
Sockets support. VM Sockets allows communication between virtual
machines and the hypervisor. VM Sockets is able to use different
hyervisor neutral transport to transfer data. Currently, only VMware
VMCI transport is supported.
This series introduces virtio transport for VM Sockets.
Any comments are appreciated! Thanks!
Code:
=========================
1) kernel bits
git://github.com/asias/linux.git vsock
2) userspace bits:
git://github.com/asias/linux-kvm.git vsock
Howto:
=========================
Make sure you have these kernel options:
CONFIG_VSOCKETS=y
CONFIG_VIRTIO_VSOCKETS=y
CONFIG_VIRTIO_VSOCKETS_COMMON=y
CONFIG_VHOST_VSOCK=m
$ git clone git://github.com/asias/linux-kvm.git
$ cd linux-kvm/tools/kvm
$ co -b vsock origin/vsock
$ make
$ modprobe vhost_vsock
$ ./lkvm run -d os.img -k bzImage --vsock guest_cid
Test:
=========================
I hacked busybox's http server and wget to run over vsock. Start http
server in host and guest, download a 512MB file in guest and host
simultaneously for 6000 times. Manged to run the http stress test.
Also, I wrote a small libvsock.so to play the LD_PRELOAD trick and
managed to make sshd and ssh work over virito-vsock without modifying
the source code.
Why did it require hacking in the first place? Does running with kvmtool
and just doing regular networking over virtio-net running on top of vsock
achieves the same goal?
Draft VM Sockets Virtio Device spec:
=========================
Appendix K: VM Sockets Device
The virtio VM sockets device is a virtio transport device for VM Sockets. VM
Sockets allows communication between virtual machines and the hypervisor.
Configuration:
Subsystem Device ID 13
Virtqueues:
0:controlq; 1:receiveq0; 2:transmitq0 ... 2N+1:receivqN; 2N+2:transmitqN
controlq is "defined but not used", is there something in mind for it? if not,
does it make sense keeping it here? we can always re-add it to the end just
like in virtio-net.
Feature bits:
Currently, no feature bits are defined.
Device configuration layout:
Two configuration fields are currently defined.
struct virtio_vsock_config {
__u32 guest_cid;
__u32 max_virtqueue_pairs;
} __packed;
The guest_cid field specifies the guest context id which likes the guest IP
address. The max_virtqueue_pairs field specifies the maximum number of receive
and transmit virtqueue pairs (receiveq0 ... receiveqN and transmitq0 ...
transmitqN respectively; N = max_virtqueue_pairs - 1 ) that can be configured.
The driver is free to use only one virtqueue pairs, or it can use more to
achieve better performance.
How does the driver tell the device how many vqs it's planning on actually
using?
or is it assumed that all of them are in use?
Device Initialization:
The initialization routine should discover the device's virtqueues.
Device Operation:
Packets are transmitted by placing them in the transmitq0..transmitqN, and
buffers for incoming packets are placed in the receiveq0..receiveqN. In each
case, the packet itself is preceded by a header:
struct virtio_vsock_hdr {
__u32 src_cid;
__u32 src_port;
__u32 dst_cid;
__u32 dst_port;
__u32 len;
__u8 type;
__u8 op;
__u8 shut;
__u64 fwd_cnt;
__u64 buf_alloc;
} __packed;
src_cid and dst_cid: specify the source and destination context id.
src_port and dst_port: specify the source and destination port.
len: specifies the size of the data payload, it could be zero if no data
payload is transferred.
type: specifies the type of the packet, it can be SOCK_STREAM or SOCK_DGRAM.
op: specifies the operation of the packet, it is defined as follows.
enum {
VIRTIO_VSOCK_OP_INVALID = 0,
VIRTIO_VSOCK_OP_REQUEST = 1,
VIRTIO_VSOCK_OP_NEGOTIATE = 2,
VIRTIO_VSOCK_OP_OFFER = 3,
VIRTIO_VSOCK_OP_ATTACH = 4,
VIRTIO_VSOCK_OP_RW = 5,
VIRTIO_VSOCK_OP_CREDIT = 6,
VIRTIO_VSOCK_OP_RST = 7,
VIRTIO_VSOCK_OP_SHUTDOWN = 8,
};
shut: specifies the shutdown mode when the socket is being shutdown. 1 is for
receive shutdown, 2 is for transmit shutdown, 3 is for both receive and transmit
shutdown.
fwd_cnt: specifies the the number of bytes the receiver has forwarded to
userspace.
For the previous packet? For the entire session? Reading ahead makes it clear
but
it's worth mentioning here the context just to make it easy for implementers.
buf_alloc: specifies the size of the receiver's recieve buffer in bytes.
receive
Virtio VM socket connection creation:
1) Client sends VIRTIO_VSOCK_OP_REQUEST to server
2) Server reponses with VIRTIO_VSOCK_OP_NEGOTIATE to client
3) Client sends VIRTIO_VSOCK_OP_OFFER to server
4) Server responses with VIRTIO_VSOCK_OP_ATTACH to client
Virtio VM socket credit update:
Virtio VM socket uses credit-based flow control. The sender maintains tx_cnt
which counts the totoal number of bytes it has sent out, peer_fwd_cnt which
total
counts the totoal number of byes the receiver has forwarded, and peer_buf_alloc
total
which is the size of the receiver's receive buffer. The sender can send no more
than the credit the receiver gives to the sender: credit = peer_buf_alloc -
Thanks,
Sasha
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