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.Dd September 27, 2024
.Dt VMM 4
.Os
.Sh NAME
.Nm vmm.ko
.Nd "bhyve virtual machine monitor"
.Sh SYNOPSIS
To load the driver as a module at boot, add this line to
.Xr loader.conf 5 :
.Bd -literal -offset indent
.Cd vmm_load="YES"
.Ed
.Pp
The module can also be loaded manually with
.Xr kldload 8 :
.Bd -literal -offset indent
kldload vmm
.Ed
.Sh DESCRIPTION
.Nm
provides the kernel portion of the
.Xr bhyve 4
hypervisor.
.Pp
An Intel CPU with VT-x/EPT or AMD CPU with SVM support is required.
.Pp
PCI device passthrough to a virtual machine requires
hardware with VT-d support.
.Sh PCI PASSTHROUGH
When the hardware supports VT-d, and
.Nm
has been loaded at boot time,
PCI devices can be reserved for use by the hypervisor.
Entries consisting of the PCI
.Ar bus Ns / Ns Ar slot Ns / Ns Ar function
are added to the
.Va pptdevs
.Xr loader.conf 5
variable.
Additional entries are separated by spaces.
Host PCI devices that match an entry will be assigned to the hypervisor
and will not be probed by
.Fx
device drivers.
See the
.Sx EXAMPLES
section below for sample usage.
.Pp
Note that
.Nm vmm
must be given first the right of refusal to all
.Xr pci 4
devices it may need to claim.
As a result, the
.Nm vmm
kernel module almost certainly needs to be loaded from
.Xr loader.conf 5
rather than by adding it to
.Va kld_list in
.Xr rc.conf 5 .
.Pp
A large number of PCI device entries may require a string longer than the
128-character limit of
.Xr loader.conf 5
variables.
The
.Va pptdevs2
and
.Va pptdevs3
variables can be used for additional entries.
.Sh LOADER TUNABLES
Tunables can be set at the
.Xr loader 8
prompt before booting the kernel or stored in
.Xr loader.conf 5 .
.Bl -tag -width indent
.It Va hw.vmm.maxcpu
Maximum number of virtual CPUs.
The default is the number of physical CPUs in the system.
.El
.Sh EXAMPLES
Reserve three PCI devices for use by the hypervisor: bus 10 slot 0 function 0,
bus 6 slot 5 function 0, and bus 6 slot 5 function 1.
.Bd -literal -offset indent
pptdevs="10/0/0 6/5/0 6/5/1"
.Ed
.Pp
It is possible to detach
.Va ppt
from a PCI device without rebooting the host machine and then attach a host
driver, using the
.Xr devctl 8
utility.
Suppose
.Va ppt
is currently attached to
.Va pci0:0:1:0
and we want the host's
.Xr xhci 4
driver to be attached instead:
.Bd -literal -offset indent
# devctl set driver -f pci0:0:1:0 xhci
.Ed
.Pp
The same can be applied to attach
.Va ppt
back:
.Bd -literal -offset indent
# devctl set driver -f pci0:0:1:0 ppt
.Ed
.Sh SEE ALSO
.Xr bhyve 4 ,
.Xr loader.conf 5 ,
.Xr bhyve 8 ,
.Xr bhyveload 8 ,
.Xr devctl 8 ,
.Xr kldload 8
.Sh HISTORY
.Nm vmm.ko
first appeared in
.Fx 10.0 .
.Sh AUTHORS
.An Neel Natu Aq neel@freebsd.org
.An Peter Grehan Aq grehan@freebsd.org