--- wikisrc/ports/xen/howto.mdwn	2020/11/15 14:37:20	1.181
+++ wikisrc/ports/xen/howto.mdwn	2020/11/15 14:47:55	1.182
@@ -8,7 +8,28 @@ systems which operate in an unprivileged
 from the domU systems are forwarded by the Xen hypervisor to the dom0 to be
 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="""
 Style of guest	|Supported by NetBSD
@@ -21,6 +42,7 @@ PVH		|current-only (domU, dom0 not yet)
 In Para-Virtualized (PV) mode, the guest OS does not attempt to access
 hardware directly, but instead makes hypercalls to the hypervisor; PV
 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
 support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs.
@@ -28,27 +50,33 @@ The dom0 runs qemu to emulate hardware.
 
 In PVHVM mode, the guest runs as HVM, but additionally can use PV
 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
 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
 is that qemu is not needed; the hypervisor can do the emulation that
 is required.  Thus, a dom0 can be 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
 in the dom0 section.)
 
-This HOWTO presumes a basic familiarity with the Xen system
-architecture, with installing NetBSD on i386/amd64 hardware, and with
-installing software from pkgsrc.  See also the [Xen
-website](http://www.xenproject.org/).
+## CPU Architecture
 
-[[!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
 xenkernel and xentools.  We will refer only to the kernel versions,
@@ -79,16 +107,6 @@ because the hypercall interface has rema
 Older Xen had a python-based management tool called xm, now replaced
 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
 
 In order to install a NetBSD as a dom0, one must first install a normal