Re: [Qemu-devel] [virtio-comment] [PATCH] *** Vhost-pci RFC v2 ***

[Michael S. Tsirkin]

On Mon, Jun 27, 2016 at 02:01:24AM +0000, Wang, Wei W wrote:
> On Sun 6/19/2016 10:14 PM, Wei Wang wrote:
> > This RFC proposes a design of vhost-pci, which is a new virtio device type.
> > The vhost-pci device is used for inter-VM communication.
> > 
> > Changes in v2:
> > 1. changed the vhost-pci driver to use a controlq to send acknowledgement
> >    messages to the vhost-pci server rather than writing to the device
> >    configuration space;
> > 
> > 2. re-organized all the data structures and the description layout;
> > 
> > 3. removed the VHOST_PCI_CONTROLQ_UPDATE_DONE socket message, which
> > is redundant;
> > 
> > 4. added a message sequence number to the msg info structure to identify
> > socket
> >    messages, and the socket message exchange does not need to be blocking;
> > 
> > 5. changed to used uuid to identify each VM rather than using the QEMU 
> > process
> >    id
> > 
> 
> One more point should be added is that the server needs to send periodic 
> socket messages to check if the driver VM is still alive. I will add this 
> message support in next version.  (*v2-AR1*)

Question would be, does it mean guest is alive or QEMU/vhost
thread running is alive? And how do you distinguish a guest that
crashed from guest that is scheduled out?

Hypervisors generally have ways to detect and handle crashed
and stuck guests. It is likely a better idea to have a single
device to detect this than have each device send keep-alive
interrupts, interfering with the guest.

Given this is not a networking
transport, isn't it enough to handle this simply as a guest reset?
you have to handle it anyway.


> > Wei Wang (1):
> >   Vhost-pci RFC v2: a new virtio device for inter-VM communication
> > 
> >  vhost-pci.patch | 341
> > ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
> >  1 file changed, 341 insertions(+)
> >  create mode 100755 vhost-pci.patch
> > 
> 
> Hi Michael,
> 
> Would you be able to look into the design? Thanks.
> 
> Best,
> Wei