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From: "Michael S. Tsirkin" <firstname.lastname@example.org>
To: "Wang, Wei W" <email@example.com>
Cc: "firstname.lastname@example.org" <email@example.com>,
Stefan Hajnoczi <firstname.lastname@example.org>,
Paolo Bonzini <email@example.com>,
"Yamahata, Isaku" <firstname.lastname@example.org>,
"Nakajima, Jun" <email@example.com>,
"Kleen, Andi" <firstname.lastname@example.org>
Subject: Re: [RFC] hypercall-vsock: add a new vsock transport
Date: Wed, 10 Nov 2021 05:50:04 -0500 [thread overview]
Message-ID: <email@example.com> (raw)
On Wed, Nov 10, 2021 at 07:12:36AM +0000, Wang, Wei W wrote:
> We plan to add a new vsock transport based on hypercall (e.g. vmcall on Intel
> 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
> 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.
hypercalls are fundamentally hypervisor dependent though.
Assuming you can carve up a hypervisor independent hypercall,
using it for something as mundane and specific as vsock for TDX
seems like a huge overkill. For example, virtio could benefit from
faster vmexits that hypercalls give you for signalling.
How about a combination of virtio-mmio and hypercalls for fast-path
> 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).
Next thing people will try to do is implement a bunch of other device on
top of it. virtio used pci simply because everyone implements pci. And
the reason for *that* is because implementing a basic pci bus is dead
simple, whole of pci.c in qemu is <3000 LOC.
> An example usage is the communication between MigTD and host (Page 8 at
> 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
> (e.g. bare mental implementation without OS, no PCI driver support).
Try to list drawbacks? For example, passthrough for nested virt
isn't possible unlike pci, neither are hardware implementations.
> Looking forward to your feedbacks.
next prev parent reply other threads:[~2021-11-10 10:50 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <firstname.lastname@example.org>
2021-11-10 9:34 ` Stefan Hajnoczi
2021-11-11 8:02 ` Wang, Wei W
2021-11-10 10:50 ` Michael S. Tsirkin [this message]
2021-11-11 7:58 ` Wang, Wei W
2021-11-11 15:19 ` Michael S. Tsirkin
2021-11-25 6:37 ` Jason Wang
2021-11-25 8:43 ` Wang, Wei W
2021-11-25 12:04 ` Gerd Hoffmann
2021-11-10 11:17 ` Stefano Garzarella
2021-11-10 21:45 ` Paraschiv, Andra-Irina
2021-11-11 8:14 ` Wang, Wei W
2021-11-11 8:24 ` Paolo Bonzini
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