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version 1.181, 2020/11/15 14:37:20	version 1.182, 2020/11/15 14:47:55
Line 8 systems which operate in an unprivileged	Line 8 systems which operate in an unprivileged
from the domU systems are forwarded by the Xen hypervisor to the dom0 to be	from the domU systems are forwarded by the Xen hypervisor to the dom0 to be
fulfilled.	fulfilled.

Xen supports different styles of guests; see [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM) and [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu) for upstream documentation.	This HOWTO presumes a basic familiarity with the Xen system
	architecture, with installing NetBSD on amd64 hardware, and with
	installing software from pkgsrc. See also the [Xen
	website](http://www.xenproject.org/).

	[[!toc]]

	# Overview: Versions of Xen, Styles, NetBSD

	The basic concept of Xen is that the hypervisor (xenkernel) runs on
	the hardware, and runs a privileged domain ("dom0") that can access
	disks/networking/etc. One then runs additonal unprivileged domains
	(each a "domU"), presumably to do something useful.

	This HOWTO addresses how to run a NetBSD dom0 (and hence also build
	xen itself). It also addresses how to run domUs in that environment,
	and how to deal with having a domU in a Xen environment run by someone
	else and/or not running NetBSD.

	## Guest Styles

	Xen supports different styles of guests.

[[!table data="""	[[!table data="""
Style of guest \|Supported by NetBSD	Style of guest \|Supported by NetBSD
Line 21 PVH \|current-only (domU, dom0 not yet)	Line 42 PVH \|current-only (domU, dom0 not yet)
In Para-Virtualized (PV) mode, the guest OS does not attempt to access	In Para-Virtualized (PV) mode, the guest OS does not attempt to access
hardware directly, but instead makes hypercalls to the hypervisor; PV	hardware directly, but instead makes hypercalls to the hypervisor; PV
guests must be specifically coded for Xen.	guests must be specifically coded for Xen.
	See [PV](https://wiki.xen.org/wiki/Paravirtualization_(PV\)).

In HVM mode, no guest modification is required; however, hardware	In HVM mode, no guest modification is required; however, hardware
support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs.	support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs.
Line 28 The dom0 runs qemu to emulate hardware.	Line 50 The dom0 runs qemu to emulate hardware.

In PVHVM mode, the guest runs as HVM, but additionally can use PV	In PVHVM mode, the guest runs as HVM, but additionally can use PV
drivers for efficiency.	drivers for efficiency.
	See [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM).

There have been two PVH modes: original PVH and PVHv2. Original PVH	There have been two PVH modes: original PVH and PVHv2. Original PVH
was based on PV mode and is no longer relevant at all. PVHv2 is	was based on PV mode and is no longer relevant at all. PVHv2 is
basically lightweight HVM with PV drivers. A critical feature of it	basically lightweight HVM with PV drivers. A critical feature of it
is that qemu is not needed; the hypervisor can do the emulation that	is that qemu is not needed; the hypervisor can do the emulation that
is required. Thus, a dom0 can be PVHv2.	is required. Thus, a dom0 can be PVHv2.

The source code uses PVH and config files use pvh; this refers to PVHv2.	The source code uses PVH and config files use pvh; this refers to PVHv2.
	See [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu).


At boot, the dom0 kernel is loaded as a module with Xen as the kernel.	At system boot, the dom0 kernel is loaded as a module with Xen as the kernel.
The dom0 can start one or more domUs. (Booting is explained in detail	The dom0 can start one or more domUs. (Booting is explained in detail
in the dom0 section.)	in the dom0 section.)

This HOWTO presumes a basic familiarity with the Xen system	## CPU Architecture
architecture, with installing NetBSD on i386/amd64 hardware, and with
installing software from pkgsrc. See also the [Xen
website](http://www.xenproject.org/).

[[!toc]]	Xen runs on x86_64 hardware (the NetBSD amd64 port).

# Versions and Support	There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD.

	The dom0 system should be amd64. (Instructions for i386PAE dom0 have been removed from the HOWTO.)

	The domU can be i386PAE or amd64.
	i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64.

	## Xen Versions

In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages	In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
xenkernel and xentools. We will refer only to the kernel versions,	xenkernel and xentools. We will refer only to the kernel versions,
Line 79 because the hypercall interface has rema	Line 107 because the hypercall interface has rema
Older Xen had a python-based management tool called xm, now replaced	Older Xen had a python-based management tool called xm, now replaced
by xl.	by xl.

## Architecture

Xen 4.5 and later runs on x86_64 hardware (the NetBSD amd64 port).
There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD.

The dom0 system should be amd64. (Instructions for i386PAE dom0 have been removed from the HOWTO.)

The domU can be i386PAE or amd64.
i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64.

# Creating a dom0	# Creating a dom0

In order to install a NetBSD as a dom0, one must first install a normal	In order to install a NetBSD as a dom0, one must first install a normal

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