man/man4/pvbus.4

.\"	$OpenBSD: pvbus.4,v 1.15 2023/01/07 06:40:21 asou Exp $
.\"
.\" Copyright (c) 2015 Reyk Floeter <reyk@openbsd.org>
.\" Copyright (c) 2006 Jason McIntyre <jmc@openbsd.org>
.\"
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.Dd $Mdocdate: January 7 2023 $
.Dt PVBUS 4
.Os
.Sh NAME
.Nm pvbus
.Nd paravirtual device tree root
.Sh SYNOPSIS
.Cd "pvbus0 at mainbus0"
.Pp
.In sys/types.h
.In sys/ioctl.h
.In dev/pv/pvvar.h
.Sh DESCRIPTION
.Nm
is used on virtual machines that are running on hypervisors.
It provides a pseudo-bus for all paravirtual devices that do not
attach to a well-known bus like
.Xr pci 4 .
The
.Nm
driver is responsible for detecting the hypervisor interface,
checking the capabilities, attaching the paravirtual devices,
and providing access to supported information stores.
.Ss Supported hypervisors
.Bl -tag -width 13n -offset ind -compact
.It KVM
Kernel-based Virtual Machine
.It Hyper-V
Microsoft Hyper-V
.It OpenBSD
.Ox
.Xr vmm 4
.It VMware
VMware vSphere Hypervisor and ESXi
.It Xen
Xen VMM
.El
.Pp
Note that a hypervisor can attempt to emulate other hypervisors, so
multiple hypervisor interfaces may be available on the same host.
.Ss VMware paravirtual devices
.Bl -tag -width 13n -offset ind -compact
.It Xr vmt 4
VMware Tools driver and
.Dq guestinfo
information store
.El
.Ss Hyper-V paravirtual devices
.Bl -tag -width 13n -offset ind -compact
.It Xr hvn 4
Hyper-V virtual networking interface
.It Xr hvs 4
Hyper-V virtual disk
.It Xr hyperv 4
Hyper-V guest nexus device
.El
.Ss Xen paravirtual devices
.Bl -tag -width 13n -offset ind -compact
.It Xr xbf 4
Xen Blkfront virtual disk
.It Xr xen 4
Xen domU nexus device and XenStore information store
.It Xr xnf 4
Xen Netfront virtual networking interface
.El
.Sh IOCTL INTERFACE
.Nm
supports
.Xr ioctl 2
commands to exchange information with the hypervisor interface,
as implemented in the
.Xr hostctl 8
program.
Each detected hypervisor interface is available as a character special
device file,
.Pa /dev/pvbus0 ,
.Pa /dev/pvbus1 ,
etc.
All available commands use the same
.Fa pvbus_req
structure:
.Bd -literal
struct pvbus_req {
	size_t			 pvr_keylen;
	char			*pvr_key;
	size_t			 pvr_valuelen;
	char			*pvr_value;
};
.Ed
.Pp
The caller is responsible for attaching character buffers to the
.Fa pvr_key
and
.Fa pvr_value
fields and to set their length in
.Fa pvr_keylen
and
.Fa pvr_valuelen
accordingly.
All keys and values are nul-terminated strings.
.Pp
The following
.Xr ioctl 2
commands are available:
.Bl -tag -width PVBUSIOC_KVWRITE
.It Dv PVBUSIOC_KVREAD
Read the value from
.Fa pvr_key
and return it in
.Fa pvr_value .
If
.Fa pvr_valuelen
is not enough for the value,
the command will fail and
.Xr errno 2
is set to
.Er ERANGE .
.It Dv PVBUSIOC_KVTYPE
Return the type of the attached hypervisor interface as a string in
.Fa pvr_key ;
see
.Sx Supported hypervisors .
.It Dv PVBUSIOC_KVWRITE
Write the new value
.Fa pvr_value
to the key
.Fa pvr_key .
This command requires write permissions on the device file.
.El
.Sh FILES
.Bl -tag -width "/dev/pvbusX" -compact
.It /dev/pvbus Ns Ar u
.Nm
device unit
.Ar u
file.
.El
.Sh SEE ALSO
.Xr autoconf 4 ,
.Xr intro 4 ,
.Xr mainbus 4 ,
.Xr vmm 4 ,
.Xr hostctl 8
.Sh HISTORY
The
.Nm
pseudo-bus first appeared in
.Ox 5.8 .
.Sh AUTHORS
The
.Nm
pseudo-bus was written by
.An Reyk Floeter Aq Mt reyk@openbsd.org .