From:   "Wang, Wei W" <wei.w.wang@intel.com>
To:     Stefan Hajnoczi <stefanha@redhat.com>
CC:     "sgarzare@redhat.com" <sgarzare@redhat.com>,
        "davem@davemloft.net" <davem@davemloft.net>,
        "kuba@kernel.org" <kuba@kernel.org>,
        "mst@redhat.com" <mst@redhat.com>,
        Paolo Bonzini <pbonzini@redhat.com>,
        "kys@microsoft.com" <kys@microsoft.com>,
        "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
        "virtualization@lists.linux-foundation.org" 
        <virtualization@lists.linux-foundation.org>,
        "Yamahata, Isaku" <isaku.yamahata@intel.com>,
        "Nakajima, Jun" <jun.nakajima@intel.com>,
        "Kleen, Andi" <andi.kleen@intel.com>,
        Andra Paraschiv <andraprs@amazon.com>,
        "Sergio Lopez Pascual" <slp@redhat.com>
Subject: RE: [RFC] hypercall-vsock: add a new vsock transport
Thread-Topic: [RFC] hypercall-vsock: add a new vsock transport
Thread-Index: AdfR7PQwhDKKIu84SJaS6/iA/MsV5gD5igUAADxATEA=
Date:   Thu, 11 Nov 2021 08:02:27 +0000
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> From: Stefan Hajnoczi <stefanha@redhat.com>
On Wednesday, November 10, 2021 5:35 PM, Stefan Hajnoczi wrote:
> AF_VSOCK is designed to allow multiple transports, so why not. There is a cost
> to developing and maintaining a vsock transport though.

Yes. The effort could be reduced via simplifying the design as much as possible:
e.g. no ring operations - guest just sends a packet each time for the host to read.
(this transport isn't targeting for high performance)

> 
> I think Amazon Nitro enclaves use virtio-vsock and I've CCed Andra in case she
> has thoughts on the pros/cons and how to minimize the trusted computing
> base.

Thanks for adding more related person to the discussion loop.

> 
> If simplicity is the top priority then VIRTIO's MMIO transport without indirect
> descriptors and using the packed virtqueue layout reduces the size of the
> implementation:
> https://docs.oasis-open.org/virtio/virtio/v1.1/cs01/virtio-v1.1-cs01.html#x1-1
> 440002

I listed some considerations for virtio-mmio in the response to Michael.
Please have a check if any different thoughts.

Thanks,
Wei