Re: Can xenvirt pmd work in xen guest (aka DomU) without xen-vhost in Dom0 ?

[Konrad Rzeszutek Wilk <konrad@kernel.org>]

On Mon, Oct 09, 2017 at 12:13:47AM +0800, Tan, Jianfeng wrote:
> Hi,
> 
> 
> On 10/8/2017 12:54 PM, Bill Bonaparte wrote:
> > Thanks Jianfeng for taking time to reply.
> > 
> > please allow me to briefly explain why I want to run dpdk on xen.
> > our system is based on dpdk, which means we use dpdk as packet
> > receive/transmit engine,
> > and with integrated dpdk virtio/vmxnet3 driver, our system can run on
> > KVM/VMware platform .
> > this year, we have plan to run our system on AWS cloud, but I found that
> > AWS
> > uses xen as its virtualization platform, and the bus-info of nic is
> > vif-x (x could be 0,1,2...),
> > the driver used in kernel is vif. this should be para-virtualized nic
> > used on xen.
> 
> My guess is exactly as you describe. In AWS, we lack of a PMD for xen
> netfront (vif) nic. And even we got such a PMD, we still need a PMD for xen
> netback. Both are missing.
> 
> > 
> > I don't know which dpdk drvier can manage this pv nic. then I see
> > xenvirt, I think this driver can
> > did this job, like virtio can manage virtio nic which is used on kvm.
> > unfortunately, after some study work, I run testpmd successfully on xen,
> > but no packets received.
> > 
> > with the informain got from you, I know It's need to run vhost_xen at
> > dom0 so that xenvirt at domU can work.
> > but for my case, I have no change to run vhost_xen at dom0, because I
> > only can operate my own domU.
> > 
> > for this case, If I want to run system which is based on dpdk at domU,
> > what should I do?
> > appreciate any idea or suggestion from you.
> 
> What kind of performance are you seeking? Only accelerating the frontend by
> a new PMD, i.e. netfront, we can bypass the VM kernel (). But without
> accelerating the backend, it only brings limited improvement.
> 
> Not sure if anyone from Amazon or Oracle can comment?

Joao has been working on updates in the Xen PV network driver such
that there is a higher acceleration (aka recycle grants). See in xen.git
tree:
commit 30655e2bf0ce8ee50e61728e2558e0363f4af1c9
Author: Joao Martins <joao.m.martins@oracle.com>
Date:   Tue Oct 3 18:46:08 2017 +0100

    public/io/netif.h: add gref mapping control messages



This combined with the drivers that Broadcom wrote (I think that is
the name of the company that posted them a year or so ago), should
provide awesome performance.

> 
> Thanks,
> Jianfeng