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-version 1.57, 2014/12/27 00:33:45
+version 1.75, 2015/01/17 01:32:12
  Line 4  Introduction
  [![[Xen
  screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](http://www.netbsd.org/gallery/in-Action/hubertf-xen.png)
- Xen is a virtual machine monitor or hypervisor for x86 hardware
+ Xen is a hypervisor (or virtual machine monitor) for x86 hardware
  (i686-class or higher), which supports running multiple guest
- operating systems on a single physical machine.  With Xen, one uses
+ operating systems on a single physical machine.  Xen is a Type 1 or
- the Xen kernel to control the CPU, memory and console, a dom0
+ bare-metal hypervisor; one uses the Xen kernel to control the CPU,
- operating system which mediates access to other hardware (e.g., disks,
+ memory and console, a dom0 operating system which mediates access to
- network, USB), and one or more domU operating systems which operate in
+ other hardware (e.g., disks, network, USB), and one or more domU
- an unprivileged virtualized environment.  IO requests from the domU
+ operating systems which operate in an unprivileged virtualized
- systems are forwarded by the hypervisor (Xen) to the dom0 to be
+ environment.  IO requests from the domU systems are forwarded by the
- fulfilled.
+ hypervisor (Xen) to the dom0 to be fulfilled.
  Xen supports two styles of guests.  The original is Para-Virtualized
  (PV) which means that the guest OS does not attempt to access hardware
  Line 151  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:
+ support) is difficult to build.  The following are known to work or FAIL:
-         xenkernel3 netbsd-6 i386
-         xentools42 netbsd-6 i386
- The following are known to work:
+         xenkernel3 netbsd-5 amd64
+         xentools3 netbsd-5 amd64
+         xentools3=hvm netbsd-5 amd64 ????
+         xenkernel33 netbsd-5 amd64
+         xentools33 netbsd-5 amd64
          xenkernel41 netbsd-5 amd64
          xentools41 netbsd-5 amd64
+         xenkernel42 netbsd-5 amd64
+         xentools42 netbsd-5 amd64
+         xenkernel3 netbsd-6 i386 FAIL
+         xentools3 netbsd-6 i386
+         xentools3-hvm netbsd-6 i386 FAIL (dependencies fail)
+         xenkernel33 netbsd-6 i386
+         xentools33 netbsd-6 i386
          xenkernel41 netbsd-6 i386
          xentools41 netbsd-6 i386
+         xenkernel42 netbsd-6 i386
+         xentools42 netbsd-6 i386 *MIXED
+         (all 3 and 33 seem to FAIL)
+         xenkernel41 netbsd-7 i386
+         xentools41 netbsd-7 i386
+         xenkernel42 netbsd-7 i386
+         xentools42 netbsd-7 i386 ??FAIL
+ (*On netbsd-6 i386, there is a xentools42 in the 2014Q3 official builds,
+ but it does not build for gdt.)
  NetBSD as a dom0
  ================
- Line 255  For debugging, one may copy xen-debug.gz
+ Line 274  For debugging, one may copy xen-debug.gz
  to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
  useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
  in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
- of a NetBSD build.  Both xen and NetBSD may be left compressed.  (If
+ of a NetBSD build.  If using i386, use
- using i386, use releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.)
+ releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  (If using Xen
+.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen.  But you
- With Xen as the kernel, you must provide a dom0 NetBSD kernel to be
+ should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and
- used as a module; place this in /.  Suitable kernels are provided in
+ typically are) left compressed.
- releasedir/binary/kernel:
+ In a dom0 kernel, kernfs is mandatory for xend to comunicate with the
-         i386 XEN3_DOM0
+ kernel, so ensure that /kern is in fstab.  TODO: Say this is default,
-         i386 XEN3PAE_DOM0
+ or file a PR and give a reference.
-         amd64 XEN3_DOM0
- The first one is only for use with Xen 3.1 and i386-mode Xen (and you
- should not do this).  Current Xen always uses PAE on i386, but you
- should generally use amd64 for the dom0.  In a dom0 kernel, kernfs is
- mandatory for xend to comunicate with the kernel, so ensure that /kern
- is in fstab.  TODO: Say this is default, or file a PR and give a
- reference.
  Because you already installed NetBSD, you have a working boot setup
  with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
- Line 283  See boot.cfg(5) for an example.  The bas
+ Line 294  See boot.cfg(5) for an example.  The bas
          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.  In an attempt to add performance, one can also
+ allocated for domUs.  To use In an attempt to add performance, one can
- add
+ also add
          dom0_max_vcpus=1 dom0_vcpus_pin
- Line 457  Unprivileged domains (domU)
+ Line 468  Unprivileged domains (domU)
  This section describes general concepts about domUs.  It does not
  address specific domU operating systems or how to install them.  The
  config files for domUs are typically in /usr/pkg/etc/xen, and are
- typically named so that the file anme, domU name and the domU's host
+ typically named so that the file name, domU name and the domU's host
  name match.
  The domU is provided with cpu and memory by Xen, configured by the
- Line 531  anyplace, reasonable places to store dom
+ Line 542  anyplace, reasonable places to store dom
  (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
  config files), or in /u0/xen (where the vdisks are).
+ Note that loading the domU kernel from the dom0 implies that boot
+ blocks, /boot, /boot.cfg, and so on are all ignored in the domU.
  See the VPS section near the end for discussion of alternate ways to
  obtain domU kernels.
- Line 854  NetBSD as a domU in a VPS
+ Line 867  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
  virtual private server where you do not control or have access to the
- dom0.
+ dom0.  This is not intended to be an exhaustive list of VPS providers;
+ only a few are mentioned that specifically support NetBSD.
  VPS operators provide varying degrees of access and mechanisms for
  configuration.  The big issue is usually how one controls which kernel
  is booted, because the kernel is nominally in the dom0 filesystem (to
- which VPS users do not normally have acesss).
+ which VPS users do not normally have acesss).  A second issue is how
+ to install NetBSD.
  A VPS user may want to compile a kernel for security updates, to run
  npf, run IPsec, or any other reason why someone would want to change
  their kernel.
  One approach is to have an adminstrative interface to upload a kernel,
- or to select from a prepopulated list.
+ or to select from a prepopulated list.  Other approaches are pygrub
+ (deprecated) and pvgrub, which are ways to have a bootloader obtain a
+ kernel from the domU filesystem.  This is closer to a regular physical
+ computer, where someone who controls a machine can replace the kernel.
+ A second issue is multiple CPUs.  With NetBSD 6, domUs support
+ multiple vcpus, and it is typical for VPS providers to enable multiple
+ CPUs for NetBSD domUs.
+ pygrub
+ -------
+ pygrub runs in the dom0 and looks into the domU filesystem.  This
+ implies that the domU must have a kernel in a filesystem in a format
+ known to pygrub.  As of 2014, pygrub seems to be of mostly historical
+ interest.
+ pvgrub
+ ------
- Otehr approaches are pvgrub and py-grub, which are ways to start a
+ pvgrub is a version of grub that uses PV operations instead of BIOS
- bootloader from the dom0 instead of the actual domU kernel, and for
+ calls.  It is booted from the dom0 as the domU kernel, and then reads
- that loader to then load a kernel from the domU filesystem.  This is
+ /grub/menu.lst and loads a kernel from the domU filesystem.
- closer to a regular physical computer, where someone who controls a
- machine can replace the kernel.
+ [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
+ that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
+ (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
+ page](http://www.panix.com/v-colo/grub.html), which describes only
+ Linux but should be updated to cover NetBSD :-).
+ [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
+ their own kernel.  See then [prgmr.com NetBSD
+ HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
+ (which is in need of updating).
+ It appears that [grub's FFS
+ code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
+ does not support all aspects of modern FFS, but there are also reports
+ that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT
+ partition for the kernel with the intent that grub can understand it,
+ which leads to /netbsd not being the actual kernel.  One must remember
+ to update the special boot partiion.
- prmgr and pvgrub
+ Amazon
- ----------------
+ ------
- TODO: Perhaps reference panix, prmgr, amazon as interesting examples.
+ TODO: add link to NetBSD amazon howto.
- Explain what prmgr does.
  Using npf
  ---------
- Line 886  Using npf
+ Line 934  Using npf
  In standard kernels, npf is a module, and thus cannot be loadeed in a
  DOMU kernel.
- TODO: explain how to compile npf into a custom kernel, answering:
+ TODO: explain how to compile npf into a custom kernel, answering (but
+ note that the problem was caused by not booting the right kernel):
  http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html
+ TODO items for improving NetBSD/xen
+ ===================================
+ * Package Xen 4.4.
+ * Get PCI passthrough working on Xen 4.2 (or 4.4).
+ * Get pvgrub into pkgsrc, either via xentools or separately.
+ * grub
+   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary
+     fragsize/blocksize (UFS2 support may be present; the point is to
+     make it so that with any UFS1/UFS2 filesystem setup that works
+     with NetBSD grub will also work).
+     See [pkg/40258](http://gnats.netbsd.org/40258).
+   * Push patches upstream.
+   * Get UFS2 patches into pvgrub.
+ * Add support for PV ops to a version of /boot, and make it usable as
+   a kernel in Xen, similar to pvgrub.

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