PVBUS(4)

💖 NAME 💖

Okay so bestie, this is pvbus(4) — the paravirtual device tree root — and it’s living its best life in the Kernel Interfaces Manual. It’s the root of the paravirtual device tree vibe. ✨

---

✨ SYNOPSIS ✨

pvbus0 at mainbus0

#include <sys/types.h>
#include <sys/ioctl.h>
#include <dev/pv/pvvar.h>

---

🦋 DESCRIPTION 🦋

So like, pvbus is used on virtual machines that are running on hypervisors. It provides a pseudo-bus for all the paravirtual devices that do not attach to a well-known bus like pci(4). The pvbus driver is the one doing the main-character work: detecting the hypervisor interface, checking the capabilities, attaching the paravirtual devices, and providing access to supported information stores. 💅

🌈 Supported hypervisors 🌈

• KVM — Kernel-based Virtual Machine
• Hyper-V — Microsoft Hyper-V
• OpenBSD — OpenBSD vmm(4)
• VMware — VMware vSphere Hypervisor and ESXi
• Xen — Xen VMM

🫶 heads up: a hypervisor can attempt to emulate other hypervisors, so multiple hypervisor interfaces may be available on the same host.

🍓 VMware paravirtual devices 🍓

• vmt(4) — VMware Tools driver and “guestinfo” information store

🧚 Hyper-V paravirtual devices 🧚

• hvn(4) — Hyper-V virtual networking interface
• hvs(4) — Hyper-V virtual disk
• hyperv(4) — Hyper-V guest nexus device

🦋 Xen paravirtual devices 🦋

• xbf(4) — Xen Blkfront virtual disk
• xen(4) — Xen domU nexus device and XenStore information store
• xnf(4) — Xen Netfront virtual networking interface

---

💅 IOCTL INTERFACE 💅

pvbus supports ioctl(2) commands to exchange information with the hypervisor interface, as implemented in the hostctl(8) program. Each detected hypervisor interface is available as a character special device file, /dev/pvbus0, /dev/pvbus1, etc. All available commands use the same pvbus_req structure:

struct pvbus_req {
        size_t                   pvr_keylen;
        char                    *pvr_key;
        size_t                   pvr_valuelen;
        char                    *pvr_value;
};

Bestie, the caller is responsible for attaching character buffers to the pvr_key and pvr_value fields and to set their length in pvr_keylen and pvr_valuelen accordingly. All keys and values are nul-terminated strings. 💖

The following ioctl(2) commands are available:

• PVBUSIOC_KVREAD — Read the value from pvr_key and return it in pvr_value. If pvr_valuelen is not enough for the value, the command will fail and errno(2) is set to ERANGE.
• PVBUSIOC_KVTYPE — Return the type of the attached hypervisor interface as a string in pvr_key; see “Supported hypervisors”.
• PVBUSIOC_KVWRITE — Write the new value pvr_value to the key pvr_key. This command requires write permissions on the device file.

---

🎀 FILES 🎀

• /dev/pvbusu — pvbus device unit u file.

---

🔥 SEE ALSO 🔥

autoconf(4), intro(4), mainbus(4), vmm(4), hostctl(8)

---

🌸 HISTORY 🌸

The pvbus pseudo-bus first appeared in OpenBSD 5.8. ⭐

---

👑 AUTHORS 👑

The pvbus pseudo-bus was written by Reyk Floeter <reyk@openbsd.org>.

---

💌 okay that’s the whole page, bestie — footer vibes: Debian, January 7, 2023, page PVBUS(4). slay and byeee ✨