linux-kernel - Re: [RFC] hypercall-vsock: add a new vsock transport

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Message-ID: <20211110111718.5cvt6vgory3fzqld@steredhat>
Date:   Wed, 10 Nov 2021 12:17:18 +0100
From:   Stefano Garzarella <sgarzare@...hat.com>
To:     "Wang, Wei W" <wei.w.wang@...el.com>
Cc:     "davem@...emloft.net" <davem@...emloft.net>,
        "kuba@...nel.org" <kuba@...nel.org>,
        Stefan Hajnoczi <stefanha@...hat.com>,
        "mst@...hat.com" <mst@...hat.com>,
        Paolo Bonzini <pbonzini@...hat.com>,
        "kys@...rosoft.com" <kys@...rosoft.com>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "virtualization@...ts.linux-foundation.org" 
        <virtualization@...ts.linux-foundation.org>,
        "Yamahata, Isaku" <isaku.yamahata@...el.com>,
        "Nakajima, Jun" <jun.nakajima@...el.com>,
        "Kleen, Andi" <andi.kleen@...el.com>,
        Andra Paraschiv <andraprs@...zon.com>,
        Sergio Lopez Pascual <slp@...hat.com>
Subject: Re: [RFC] hypercall-vsock: add a new vsock transport

On Wed, Nov 10, 2021 at 07:12:36AM +0000, Wang, Wei W wrote:
>Hi,
>
>We plan to add a new vsock transport based on hypercall (e.g. vmcall on Intel CPUs).
>It transports AF_VSOCK packets between the guest and host, which is similar to
>virtio-vsock, vmci-vsock and hyperv-vsock.
>
>Compared to the above listed vsock transports which are designed for high performance,
>the main advantages of hypercall-vsock are:
>
>1)       It is VMM agnostic. For example, one guest working on hypercall-vsock can run on
>
>either KVM, Hyperv, or VMware.
>
>2)       It is simpler. It doesn't rely on any complex bus enumeration
>
>(e.g. virtio-pci based vsock device may need the whole implementation of PCI).
>
>An example usage is the communication between MigTD and host (Page 8 at
>https://static.sched.com/hosted_files/kvmforum2021/ef/TDX%20Live%20Migration_Wei%20Wang.pdf).
>MigTD communicates to host to assist the migration of the target (user) 
>TD.
>MigTD is part of the TCB, so its implementation is expected to be as simple as possible
>(e.g. bare mental implementation without OS, no PCI driver support).

Adding Andra and Sergio, because IIRC Firecracker and libkrun emulates 
virtio-vsock with virtio-mmio so the implementation should be simple and 
also not directly tied to a specific VMM.

Maybe this fit for your use case too, in this way we don't have to 
maintain another driver.

Thanks,
Stefano