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

["Michael S. Tsirkin" <mst@redhat.com>]

On Mon, Aug 29, 2016 at 11:24:51AM -0400, Stefan Hajnoczi wrote:
> 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*)
> 
> Either the driver VM could go down or the device VM (server) could go
> down.  In both cases there must be a way to handle the situation.
> 
> If the server VM goes down it should be possible for the driver VM to
> resume either via hotplug of a new device or through messages
> reinitializing the dead device when the server VM restarts.
> 
> Stefan


I agree. And I do not think you need to send messages just to detect
this, leave this to the hypervisor.

-- 
MST

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