Re: [Xen-devel] [dpdk-dev] [PATCH] maintainers: claim responsability for xen

["Tan, Jianfeng" <jianfeng.tan@xxxxxxxxx>]

Hi  Thomas and all,

Apologize for being an unqualified maintainer.

> -----Original Message-----
> From: Thomas Monjalon [mailto:thomas@xxxxxxxxxxxx]
> Sent: Friday, May 5, 2017 6:04 AM
> To: Joao Martins; Konrad Rzeszutek Wilk; Tan, Jianfeng
> Cc: Konrad Rzeszutek Wilk; dev@xxxxxxxx; Xen-devel
> Subject: Re: [dpdk-dev] [PATCH] maintainers: claim responsability for xen
> 
> Ping
> 
> The Xen dom0 support in DPDK seems dead.
> 
> Reminder:
> Last time we talked about, it was because of a severe bug which is not
> fixed yet:
>         http://dpdk.org/ml/archives/dev/2016-July/044207.html

For this bug, we removed the userspace memset(0) and suppose it has been done 
by kernel, however, xen0 uses __get_free_pages() kernel API to map hugepages 
and reseve memseg, I think it makes sense to zero the hugepage for xen0 in 
rte_dom0_mm kernel module (instead of some special code for xen0 in userspace) 
to keep aligned behavior.

>         http://dpdk.org/ml/archives/dev/2016-July/044376.html

It does not make any sense to upstream a netfront PMD before we have a netback 
PMD, as the legacy netback driver would be the bottleneck. Anyone has plan on 
this? And a question mark keeps in my mind that is it a must to implement 
netback in dom0?

From another perspective, instead of using netfront/netback, we can also use 
virtio/vhost as the device model; however, xl tool in xen only supports 
vhost-kernel backend instead of vhost-user backend. So anyone has plan to 
enhance xl tool so that we can accelerate dom0 just using vswitch like OVS-DPDK?

A third solution is to use xenvirtio as the frontend, and vhost_xen as the 
backend. This solution is to use virtio ring on grant table mechanism of xen. 
Honestly, I don't even know if it still work now. And to make it more usable, 
better to upstream vhost_xen inside popular vswitch like OVS-DPDK.

> The request (9 months ago) was to give more time for feedbacks:
>         http://dpdk.org/ml/archives/dev/2016-July/044847.html

Apologize again that I volunteer to maintain these files, but spend very few 
time on this.

Thanks,
Jianfeng

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