HYPER-V(4)

💖 HYPER-V(4) — hv_vmbus, the Hyper-V Virtual Machine Bus (VMBus) Driver 💖

okay bestie, sit down, grab a strawberry 🍓, because we're talking about hv_vmbus — the Hyper-V Virtual Machine Bus, aka VMBus, driver. this is a Kernel Interfaces Manual page and it's lowkey iconic. let's get into it 🫶

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✨ NAME ✨

hv_vmbus — the Hyper-V Virtual Machine Bus (VMBus) Driver. that's it, that's the name, no notes 💅

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🌈 SYNOPSIS 🌈

so if you wanna compile this driver into the kernel (yes, into the actual kernel, main character energy), you gotta place these lines in the system kernel configuration file:

device hyperv
device pci

that's the whole vibe check right there ✨

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🦋 DESCRIPTION 🦋

hv_vmbus provides a high performance communication interface between guest and root partitions in Hyper-V. and what even is Hyper-V? it's a hypervisor-based virtualization technology from Microsoft, no cap. 🪟

Hyper-V supports isolation in terms of a partition. and a partition? a partition is a logical unit of isolation, supported by the hypervisor, in which operating systems execute. periodt. 💫

okay so here's the tea about how it's all set up 🍵:

• The Microsoft hypervisor must have at least one parent, or root, partition, and that one runs a Windows Server operating system.
• The virtualization stack runs in the parent partition and has direct access to the hardware devices.
• The root partition then creates the child partitions, and those host the guest operating systems.

now for the child partitions, because this part matters 👑

Child partitions do not have direct access to other hardware resources. instead, they get presented a virtual view of the resources, as virtual devices (VDevs). and when a request goes out to a virtual device? it gets redirected — either via the VMBus or the hypervisor — to the devices in the parent partition, which handles the requests. the parent partition is literally doing all the work, fr fr 😭

so the VMBus itself is a logical inter-partition communication channel. here's the roster 📋:

1. The parent partition hosts Virtualization Service Providers (VSPs), which communicate over the VMBus to handle device access requests from child partitions.
2. Child partitions host Virtualization Service Consumers (VSCs), which redirect device requests to VSPs in the parent partition via the VMBus.

and the Hyper-V VMBus driver defines and implements the interface that facilitate high performance bi-directional communication between the VSCs and VSPs. All VSCs utilize the VMBus driver. every single one. all of them. 💖

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🔥 SEE ALSO 🔥

• hv_netvsc(4)
• hv_storvsc(4)
• hv_utils(4)

go read those too bestie, they're the friend group 🌸

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👑 HISTORY 👑

Support for hv_vmbus first appeared in FreeBSD 10.0. 🎉

and the driver was developed through a joint effort between Citrix Incorporated, Microsoft Corporation, and Network Appliance Incorporated. three whole companies collaborating, that's a collab we love to see 🤝✨

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🎀 AUTHORS 🎀

FreeBSD support for hv_vmbus was first added by the Microsoft BSD Integration Services Team <bsdic@microsoft.com>. thank you for your service 🫡💜

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and that's the page, bestie! this one came from the Debian edition, dated September 10, 2013, and it lives under the name HYPER-V(4) in the manual. go forth and virtualize responsibly 💅🌈💖