Re: 回复: FW: [PATCH] vhost-user: add VIRTIO_F_IN_ORDER and VIRTIO_F_NOTIFICATION_DATA feature

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

On Fri, Feb 02, 2024 at 10:27:33AM +0000, Rick Zhong wrote:
> Hi Eugenio and Michael,
> 
> Let me make it more clear about the target for this patch. Currently Corigine is developing the vDPA features on NIC which are based on the QEMU vhost-vdpa/vhost-user backend. These two virtio features are helpful in data plane performance.
> 
> In my understanding, these two virtio features are defined as part of the basic facilities of a common virtio device, which means they can be utilized by virtio-net, virtio-blk, virtio-fs... whatever backend. To implement, it is beyond the team's knowledge to handle these for all kinds of backends. So I'd prefer to set them off by default and raise an warning for other type of backends, except vhost-vdpa/vhost-user.
> 
> Best Regards,
> Rick Zhong

Yes, you should set it off by default.  No, just skipping implementation
won't cut it.  It is understandable that you just want your own use-case
addressed and it is annoying to get roped in to do some work on qemu.
However, such is the cost of doing this business.  If instead we add
hacks like the warning you mention then the codebase quickly becomes a
mess of special cases.  If you need this feature, you have to make it
nicely orthogonal and palatable to everyone. It is really not a lot
of coding work, mostly testing.

-- 
MST