Re: vsock virtio: questions about supporting DGRAM type

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

On Thu, Feb 11, 2021 at 10:04:34PM -0800, Jiang Wang . wrote:
> Hi guys,
> 
> I am working on supporting DGRAM type for virtio/vhost vsock. I
> already did some work and a draft code is here (which passed my tests,
> but still need some cleanup and only works from host to guest as of
> now, will add host to guest soon):
> https://github.com/Jiang1155/linux/commit/4e89736e0bce15496460ff411cb4694b143d1c3d
> qemu changes are here:
> https://github.com/Jiang1155/qemu/commit/7ab778801e3e8969ab98e44539943810a2fb03eb
> 
> Today, I just noticed that the Asias had an old version of virtio
> which had both dgram and stream support, see this link:
> https://kvm.vger.kernel.narkive.com/BMvH9eEr/rfc-v2-0-7-introduce-vm-sockets-virtio-transport#post1
> 
> But somehow, the dgram part seems never merged to upstream linux (the
> stream part is merged). If so, does anyone know what is the reason for
> this? Did we drop dgram support for some specific reason or the code
> needs some improvement?

It's not just code it's the spec that needs work.

See some issues pointed out here:

https://lists.oasis-open.org/archives/virtio-dev/201506/msg00003.html



> My current code differs from Asias' code in some ways. It does not use
> credit and does not support fragmentation.  It basically adds two virt
> queues and re-uses the existing functions for tx and rx ( there is
> somewhat duplicate code for now, but I will try to make common
> functions to reduce it). If we still want to support dgram in upstream
> linux, which way do you guys recommend? If necessary, I can try to
> base on Asias' old code and continue working on it. If there is
> anything unclear, just let me know. Thanks.
> 
> Regards,
> 
> Jiang

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