--- wikisrc/ports/xen/howto.mdwn	2021/03/09 13:57:53	1.202
+++ wikisrc/ports/xen/howto.mdwn	2021/03/15 00:11:52	1.203
@@ -1,4 +1,4 @@
-[[!meta title="Xen HowTo and Status"]]
+[[!meta title="Xen Status and HowTo"]]
 
 Xen is a Type 1 hypervisor which supports running multiple guest operating
 systems on a single physical machine. One uses the Xen kernel to control the
@@ -8,15 +8,19 @@ systems which operate in an unprivileged
 from the domU systems are forwarded by the Xen hypervisor to the dom0 to be
 fulfilled.
 
-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/).
-
-This document also provides status on what Xen things work on NetBSD
+This document provides status on what Xen things work on NetBSD
 (upstream documentation might say something works if it works on some
 particular Linux system).
 
+This document is also a HOWTO that 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/).
+
+If this document says that something works, and you find that it does
+not, it is best to ask on port-xen and if you are correct to file a
+PR.
+
 [[!toc]]
 
 # Overview
@@ -39,11 +43,11 @@ approach and limits discussion of altern
 Xen supports different styles of guests.
 
 [[!table data="""
-Style of guest	|Supported by NetBSD
-PV		|Yes (dom0, domU)
-HVM		|Yes (domU)
-PVHVM		|current-only (domU)
-PVH		|current-only (domU, dom0 not yet)
+Style of guest	|description				|NetBSD dom0?	|NetBSD domU?
+PV		|Paravirtualization (hypercalls)   	|yes		|yes
+HVM		|unmodified guest - domU perceives HW	|N/A		|yes
+PVHVM		|Like HVM but also PV drivers		|N/A		|current only
+PVH		|					|not yet	|current only
 """]]
 
 In Para-Virtualized (PV) mode, the guest OS does not attempt to access
@@ -61,12 +65,13 @@ drivers for efficiency.  Therefore it is
 PVHVM dom0.  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).
+was based on PV mode and is no longer relevant at all.  Therefore
+PVHv2 is abreviated PVH.  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, but NB that
+this refers to PVHv2.  See
+[PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu).
 
 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
@@ -108,15 +113,25 @@ by xl.
 Xen has been supported in NetBSD for a long time, at least since 2005.
 Initially Xen was PV only.
 
-NetBSD 8 and up support PV and HVM modes.
-
-Support for PVHVM and PVH is available only in NetBSD-current.
-
-NetBSD up to and including NetBSD 9 as a dom0 does not run SMP,
-because some drivers are not yet safe for this.  NetBSD-current
-supports SMP in dom0.
-
-NetBSD, when run as a domU, can and does typically run SMP.
+NetBSD has supported PV for a very long time, in both dom0 and domU.
+NetBSD >=8 supports HVM mode as a domU (HVM as a dom0 does not make
+sense).
+
+Support for PVHVM and PVH is available only in NetBSD-current; this is
+currently somewhat experimental, although PVHVM appears reasonably
+solid.
+
+NetBSD up to and including NetBSD 9 as a dom0 cannot safely run SMP.
+Even if one added "options MULTIPROCESSOR" and configured multiple
+vcpus, the kernel is likely to crash because of drivers without
+adequate locking.
+
+NetBSD-current supports SMP in dom0, and XEN3_DOM0 includes "options
+MULTIPROCESSOR".
+
+NetBSD (since NetBSD 6), when run as a domU, can run SMP, using
+multiple CPUs if provided.  The XEN3_DOMU kernel is built
+with "options MULITPROCESSOR".
 
 Note that while Xen 4.13 is current, the kernel support is still
 called XEN3, because the hypercall interface has not changed