--- wikisrc/ports/xen/howto.mdwn	2020/04/03 10:48:35	1.168
+++ wikisrc/ports/xen/howto.mdwn	2020/11/13 19:43:26	1.175
@@ -8,21 +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 guest:
+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.
 
 [[!table data="""
 Style of guest	|Supported by NetBSD
 PV		|Yes (dom0, domU)
 HVM		|Yes (domU)
-PVHVM		|No
-PVH		|No
+PVH		|current-only (domU, dom0 not yet)
+PVHVM		|current-only (domU)
 """]]
 
 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. 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.
+guests must be specifically coded for Xen.
+
+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.
+
+In PVH mode, the guest uses PV interfaces for IO and native interfaces for everything else.
+
+In PVHVM mode, the guest mostly runs as HVM, but can use PV drivers for efficiency.
+
+\todo Explain about "HVM with PV drivers".
 
 At 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
@@ -35,7 +42,7 @@ website](http://www.xenproject.org/).
 
 [[!toc]]
 
-#Versions and Support
+# Versions and Support
 
 In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
 xenkernel and xentools.  We will refer only to the kernel versions,
@@ -337,7 +344,7 @@ will trigger controlled shutdowns of all
 CPU and memory
 --------------
 
-A domain is provided with some number of vcpus, less than the number
+A domain is provided with some number of vcpus, up to the number
 of CPUs seen by the hypervisor. For a domU, it is controlled
 from the config file by the "vcpus = N" directive.
 
@@ -630,7 +637,15 @@ note that only the "xpci" lines are unus
         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
 
 
-#NetBSD as a domU in a VPS
+# Specific Issues
+
+## domU
+
+[NetBSD 5 is known to panic.]
+(http://mail-index.netbsd.org/port-xen/2018/04/17/msg009181.html)
+(However, NetBSD 5 systems should be updated to a supported version.)
+
+# NetBSD as a domU in a VPS
 
 The bulk of the HOWTO is about using NetBSD as a dom0 on your own
 hardware.  This section explains how to deal with Xen in a domU as a