Re: [Qemu-devel] [RFC 0/2] virtio-vhost-user: add virtio-vhost-user device

[Wei Wang]

On 01/23/2018 07:12 PM, Stefan Hajnoczi wrote:
> On Mon, Jan 22, 2018 at 07:09:06PM +0800, Wei Wang wrote:
> > On 01/19/2018 09:06 PM, Stefan Hajnoczi wrote:
> >
> >
> >   - Suppose in the future there is also a kernel virtio-vhost-user driver as
> > other PCI devices, can we unbind the kernel driver first, and then bind the
> > device to the dpdk driver? A normal PCI device should be able to smoothly
> > switch between the kernel driver and dpdk driver.
> It depends what you mean by "smoothly switch".
>
> If you mean whether it's possible to go from a kernel driver to
> vfio-pci, then the answer is yes.
>
> But if the kernel driver has an established vhost-user connection then
> it will be closed.  This is the same as reconnecting with AF_UNIX
> vhost-user.

Actually not only the case of switching to testpmd after kernel 
establishes the connection, but also for several runs of testpmd. That 
is, if we run testpmd, then exit testpmd. I think the second run of 
testpmd won't work. I'm thinking about caching the received master msgs 
in QEMU when virtio_vhost_user_parse_m2s().

Btw, I'm trying to run the code, but couldn't bind the virito-vhost-user 
device to vfio-pci (reports Unknown device), not sure if it is because 
the device type is "Unclassified device".

Best,
Wei