Re: [Qemu-devel] [virtio-dev] Re: [virtio-dev] Re: [virtio-dev] Re: [PATCH v1] virtio-net: enable configurable tx queue size

[Michael S. Tsirkin]

On Fri, Jun 16, 2017 at 04:57:01PM +0800, Jason Wang wrote:
> 
> 
> On 2017年06月16日 11:22, Michael S. Tsirkin wrote:
> > > I think the issues can be solved by VIRTIO_F_MAX_CHAIN_SIZE.
> > > 
> > > For now, how about splitting it into two series of patches:
> > > 1) enable 1024 tx queue size for vhost-user, to let the users of 
> > > vhost-user
> > > to easily use 1024 queue size.
> > Fine with me. 1) will get property from user but override it on
> > !vhost-user. Do we need a protocol flag? It seems prudent but we get
> > back to cross-version migration issues that a04re still pending solution.
> > Marc Andre, what's the status of that work?
> > 
> > > 2) enable VIRTIO_F_MAX_CHAIN_SIZE,  to enhance robustness.
> > Rather, to support it for more backends.
> 
> Ok, if we want to support different values of max chain size in the future.
> It would be problematic for migration of cross backends, consider the case
> when migrating from 2048 (vhost-user) to 1024 (qemu/vhost-kernel).
> 
> Thanks

That's already a problem, and it's growing with each new feature.
Maxime looked at supporting vhost-user backends cross-version migration,
I think we must merge some solution sooner rather than later, preferably
by the next release.

Maxime, any update here? Do we need a meeting to reach consensus?

> > 
> > > Best,
> > > Wei
> > --