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. 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 signalling then? > 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 > > 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). > > Try to list drawbacks? For example, passthrough for nested virt isn't possible unlike pci, neither are hardware implementations. > Looking forward to your feedbacks. > > > > Thanks, > > Wei > _______________________________________________ Virtualization mailing list Virtualization@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linuxfoundation.org/mailman/listinfo/virtualization
