--- wikisrc/ports/xen/howto.mdwn	2014/12/24 15:56:04	1.35
+++ wikisrc/ports/xen/howto.mdwn	2014/12/24 16:06:38	1.37
@@ -152,6 +152,24 @@ Therefore, this HOWTO recommends running
 xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the
 dom0.  Either the i386 or amd64 of NetBSD may be used as domUs.
 
+Build problems
+--------------
+
+Ideally, all versions of Xen in pkgsrc would build on all versions of
+NetBSD on both i386 and amd64.  However, that isn't the case.  Besides
+aging code and aging compilers, qemu (included in xentools for HVM
+support) is difficult to build.  The following are known to fail:
+
+        xenkernel3 netbsd-6 i386
+        xentools42 netbsd-6 i386 
+
+The following are known to work:
+
+        xenkernel41 netbsd-5 amd64
+        xentools41 netbsd-5 amd64
+        xenkernel41 netbsd-6 i386
+        xentools41 netbsd-6 i386
+
 NetBSD as a dom0
 ================
 
@@ -251,10 +269,16 @@ beginning of your root filesystem, /boot
 
 See boot.cfg(5) for an example.  The basic line is
 
-"menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M"
+        menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
 
 which specifies that the dom0 should have 256M, leaving the rest to be
-allocated for domUs.
+allocated for domUs.  In an attempt to add performance, one can also
+add
+
+        dom0_max_vcpus=1 dom0_vcpus_pin
+
+to force only one vcpu to be provided (since NetBSD dom0 can't use
+more) and to pin that vcpu to a physical cpu.  TODO: benchmark this.
 
 As with non-Xen systems, you should have a line to boot /netbsd (a
 kernel that works without Xen) and fallback versions of the non-Xen
@@ -584,7 +608,7 @@ working vif-bridge is also provided with
 
     #!/bin/sh
     #============================================================================
-    # $NetBSD: howto.mdwn,v 1.34 2014/12/24 15:55:32 gdt Exp $
+    # $NetBSD: howto.mdwn,v 1.36 2014/12/24 16:02:49 gdt Exp $
     #
     # /usr/pkg/etc/xen/vif-bridge
     #