Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.158 and 1.189

version 1.158, 2018/09/05 09:16:10 version 1.189, 2020/11/19 13:55:58
Line 8  systems which operate in an unprivileged Line 8  systems which operate in an unprivileged
 from the domU systems are forwarded by the Xen hypervisor to the dom0 to be  from the domU systems are forwarded by the Xen hypervisor to the dom0 to be
 fulfilled.  fulfilled.
   
 Xen supports different styles of guest:  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
   
   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.
   
   There are many choices one can make; the HOWTO recommends the standard
   approach and limits discussion of alternatives in many cases.
   
   ## Guest Styles
   
   Xen supports different styles of guests.
   
 [[!table data="""  [[!table data="""
 Style of guest  |Supported by NetBSD  Style of guest  |Supported by NetBSD
 PV              |Yes (dom0, domU)  PV              |Yes (dom0, domU)
 HVM             |Yes (domU)  HVM             |Yes (domU)
 PVHVM           |No  PVHVM           |current-only (domU)
 PVH             |No  PVH             |current-only (domU, dom0 not yet)
 """]]  """]]
   
 In Para-Virtualized (PV) mode, the guest OS does not attempt to access  In Para-Virtualized (PV) mode, the guest OS does not attempt to access
 hardware directly, but instead makes hypercalls to the hypervisor; PV  hardware directly, but instead makes hypercalls to the hypervisor; PV
 guests must be specifically coded for Xen. In HVM mode, no guest  guests must be specifically coded for Xen.
 modification is required; however, hardware support is required, such  See [PV](https://wiki.xen.org/wiki/Paravirtualization_(PV\)).
 as VT-x on Intel CPUs and SVM on AMD CPUs.  
   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.
   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  The dom0 can start one or more domUs.  (Booting is explained in detail
 in the dom0 section.)  in the dom0 section.)
   
 This HOWTO presumes a basic familiarity with the Xen system  ## CPU Architecture
 architecture, with installing NetBSD on i386/amd64 hardware, and with  
 installing software from pkgsrc.  See also the [Xen  Xen runs on x86_64 hardware (the NetBSD amd64 port).
 website](http://www.xenproject.org/).  
   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.)
   
 This HOWTO attempts to address both the case of running a NetBSD dom0  The domU can be i386PAE or amd64.
 on hardware and running domUs under it (NetBSD and other), and also  i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64.
 running NetBSD as a domU in a VPS.  
   
 Versions and Support  ## Xen Versions
 ====================  
   
 In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages  In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
 xenkernel and xentools.  We will refer only to the kernel versions,  xenkernel and xentools.  We will refer only to the kernel versions,
Line 49  Versions available in pkgsrc: Line 89  Versions available in pkgsrc:
   
 [[!table data="""  [[!table data="""
 Xen Version     |Package Name   |Xen CPU Support        |EOL'ed By Upstream  Xen Version     |Package Name   |Xen CPU Support        |EOL'ed By Upstream
 4.2             |xenkernel42    |32bit, 64bit           |Yes  4.11            |xenkernel411   |x86_64                 |No
 4.5             |xenkernel45    |64bit                  |Yes  4.13            |xenkernel413   |x86_64                 |No
 4.6             |xenkernel46    |64bit                  |Partially  
 4.8             |xenkernel48    |64bit                  |No  
 4.11            |xenkernel411   |64bit                  |No  
 """]]  """]]
   
 See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).  See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
   
 Multiprocessor (SMP) support in NetBSD differs depending on the domain:  Older Xen had a python-based management tool called xm, now replaced
   by xl.
   
 [[!table data="""  ## NetBSD versions
 Domain          |Supports SMP  
 dom0            |No  
 domU            |Yes  
 """]]  
   
 Note: NetBSD support is called XEN3. However, it does support Xen 4,  Xen has been supported in NetBSD for a long time, at least since 2005.
 because the hypercall interface has remained identical.  Initially Xen was PV only.
   
 Architecture  NetBSD 8 and up support PV and HVM modes.
 ------------  
   
 Xen itself runs on x86_64 hardware.  Support for PVHVM and PVH is available only in NetBSD-current.
   
 The dom0 system, plus each domU, can be either i386PAE or amd64.  NetBSD as a dom0 does not run SMP, because some drivers are not yet
 i386 without PAE is not supported.  safe for this.  \todo Link to more information about what needs work.
   
 The standard approach is to use NetBSD/amd64 for the dom0.  NetBSD, when run as a domU, can and does typically run SMP.
   
 To use an i386PAE dom0, one must build or obtain a 64bit Xen kernel and  Note: NetBSD support is called XEN3.  However, it does support Xen 4,
 install it on the system.  because the hypercall interface has remained identical.
   
 For domUs, i386PAE is considered as  
 [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)  
 than amd64.  
   
 NetBSD as a dom0  # Creating a NetBSD dom0
 ================  
   
 In order to install a NetBSD as a dom0, one must first install a normal  In order to install a NetBSD as a dom0, one must first install a normal
 NetBSD system, and then pivot the install to a dom0 install by changing  NetBSD system, and then pivot the install to a dom0 install by changing
Line 97  In 2018-05, trouble booting a dom0 was r Line 125  In 2018-05, trouble booting a dom0 was r
 512M it worked reliably.  This does not make sense, but if you see  512M it worked reliably.  This does not make sense, but if you see
 "not ELF" after Xen boots, try increasing dom0 RAM.  "not ELF" after Xen boots, try increasing dom0 RAM.
   
 Installation of NetBSD  ## Installation of NetBSD
 ----------------------  
   
 [Install NetBSD/amd64](/guide/inst/)  [Install NetBSD/amd64](/guide/inst/)
 just as you would if you were not using Xen.  just as you would if you were not using Xen.
   Therefore, use the most recent release, or a build from the most recent stable branch.
   
 Installation of Xen  ## Installation of Xen
 -------------------  
   
 We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as  Use the most recent version of Xen in pkgsrc, unless the DESCR says that it is not suitable.
 dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.  Therefore, choose 4.13.
   In the dom0, install xenkernel413 and xentools413 from pkgsrc.
   
 Once this is done, install the Xen kernel itself:  Once this is done, copy the Xen kernel from where pkgsrc puts it to
   where the boot process will be able to find it:
   
 [[!template id=programlisting text="""  [[!template id=programlisting text="""
 # cp /usr/pkg/xen48-kernel/xen.gz /  # cp -p /usr/pkg/xen413-kernel/xen.gz /
 """]]  """]]
   
 Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory, copied from  Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such kernel
 `releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz` of a NetBSD build.  can either be compiled manually, or downloaded from the NetBSD FTP, for
   example at:
   
   [[!template id=programlisting text="""
   ftp.netbsd.org/pub/NetBSD/NetBSD-9.1/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
   """]]
   
 Add a line to /boot.cfg to boot Xen:  Add a line to /boot.cfg to boot Xen:
   
Line 124  Add a line to /boot.cfg to boot Xen: Line 158  Add a line to /boot.cfg to boot Xen:
 menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M  menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
 """]]  """]]
   
 which specifies that the dom0 should have 512MB of ram, leaving the rest  This specifies that the dom0 should have 512MB of ram, leaving the rest
 to be allocated for domUs.  To use a serial console, use  to be allocated for domUs.
   
   NB: This says add, not replace, so that you will be able to boot a
   NetBSD kernel without Xen.  Once Xen boots ok, you may want to set it
   as default.
   
   To use a serial console, add settings as follows:
   
 [[!template id=filecontent name="/boot.cfg" text="""  [[!template id=filecontent name="/boot.cfg" text="""
 menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1  menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
Line 141  itself uses (in this case, the serial po Line 181  itself uses (in this case, the serial po
 In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`,  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  to force only one vcpu to be provided (since NetBSD dom0 can't use
 more) and to pin that vcpu to a physical CPU. Xen has  more) and to pin that vcpu to a physical CPU. Xen has
 [many boot options](http://xenbits.xenproject.org/docs/4.8-testing/misc/xen-command-line.html),  [many boot options](http://xenbits.xenproject.org/docs/4.13-testing/misc/xen-command-line.html),
 and other than dom0 memory and max_vcpus, they are generally not  and other than dom0 memory and max_vcpus, they are generally not
 necessary.  necessary.
   
 Enable `xencommons`:  Ensure that the boot scripts installed in
   `/usr/pkg/share/examples/rc.d` are in `/etc/rc.d`, either because you
   have `PKG_RCD_SCRIPTS=yes`, or manually.  (This is not special to Xen,
   but a normal part of pkgsrc usage.)
   
   Set `xencommons=YES` in rc.conf:
   
 [[!template id=filecontent name="/etc/rc.conf" text="""  [[!template id=filecontent name="/etc/rc.conf" text="""
 xencommons=YES  xencommons=YES
 """]]  """]]
   
   \todo Recommend for/against xen-watchdog.
   
 Now, reboot so that you are running a DOM0 kernel under Xen, rather  Now, reboot so that you are running a DOM0 kernel under Xen, rather
 than GENERIC without Xen.  than GENERIC without Xen.
   
 TODO: Recommend for/against xen-watchdog.  
   
 Once the reboot is done, use `xl` to inspect Xen's boot messages,  Once the reboot is done, use `xl` to inspect Xen's boot messages,
 available resources, and running domains.  For example:  available resources, and running domains.  For example:
   
Line 182  the state when the new xenstored starts. Line 227  the state when the new xenstored starts.
 make this work, one should not expect to be able to restart xenstored  make this work, one should not expect to be able to restart xenstored
 (and thus xencommons).  There is currently no reason to expect that  (and thus xencommons).  There is currently no reason to expect that
 this will get fixed any time soon.  this will get fixed any time soon.
   \todo Confirm if this is still true in 2020.
   
 anita (for testing NetBSD)  ## Xen-specific NetBSD issues
 --------------------------  
   
 With the setup so far (assuming 4.8/xl), one should be able to run  
 anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as  
 root, because anita must create a domU):  
   
 [[!template id=programlisting text="""  
 anita --vmm=xl test file:///usr/obj/i386/  
 """]]  
   
 Xen-specific NetBSD issues  
 --------------------------  
   
 There are (at least) two additional things different about NetBSD as a  There are (at least) two additional things different about NetBSD as a
 dom0 kernel compared to hardware.  dom0 kernel compared to hardware.
Line 209  options as GENERIC.  While it is debatab Line 243  options as GENERIC.  While it is debatab
 bug, users should be aware of this and can simply add missing config  bug, users should be aware of this and can simply add missing config
 items if desired.  items if desired.
   
 Updating NetBSD in a dom0  Finally, there have been occasional reports of trouble with X11
 -------------------------  servers in NetBSD as a dom0.
   
   ## Updating Xen in a dom0
   
   Basically, update the xenkernel and xentools packages and copy the new
   Xen kernel into place, and reboot.  This procedure should be usable to
   update to a new Xen release, but the reader is reminded that having a
   non-Xen boot methods was recommended earlier.
   
   ## Updating NetBSD in a dom0
   
 This is just like updating NetBSD on bare hardware, assuming the new  This is just like updating NetBSD on bare hardware, assuming the new
 version supports the version of Xen you are running.  Generally, one  version supports the version of Xen you are running.  Generally, one
Line 220  and adjusts `/etc`. Line 263  and adjusts `/etc`.
 Note that one must update both the non-Xen kernel typically used for  Note that one must update both the non-Xen kernel typically used for
 rescue purposes and the DOM0 kernel used with Xen.  rescue purposes and the DOM0 kernel used with Xen.
   
 Converting from grub to /boot  ## anita (for testing NetBSD)
 -----------------------------  
   With a NetBSD dom0, even without any domUs, one should be able to run
   anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
   root, because anita must create a domU):
   
   [[!template id=programlisting text="""
   anita --vmm=xl test file:///usr/obj/i386/
   """]]
   
   ## Converting from grub to /boot (historical note)
   
   These instructions are provided only to help people using grub, which
   used to be the normal approach.
   
 These instructions were used to convert a system from  These instructions were used to convert a system from
 grub to /boot.  The system was originally installed in February of  grub to /boot.  The system was originally installed in February of
Line 251  default=1 Line 306  default=1
 timeout=30  timeout=30
 """]]  """]]
   
 Upgrading Xen versions  # Unprivileged domains (domU)
 ---------------------  
   
 Minor version upgrades are trivial.  Just rebuild/replace the  
 xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg`  
 references it), and reboot.  
   
 Unprivileged domains (domU)  
 ===========================  
   
 This section describes general concepts about domUs.  It does not  This section describes general concepts about domUs.  It does not
 address specific domU operating systems or how to install them.  The  address specific domU operating systems or how to install them.  The
Line 274  mediated by Xen, and configured in the d Line 321  mediated by Xen, and configured in the d
 Entropy in domUs can be an issue; physical disks and network are on  Entropy in domUs can be an issue; physical disks and network are on
 the dom0.  NetBSD's /dev/random system works, but is often challenged.  the dom0.  NetBSD's /dev/random system works, but is often challenged.
   
 Config files  ## Config files
 ------------  
   
 See /usr/pkg/share/examples/xen/xlexample*,  See /usr/pkg/share/examples/xen/xlexample*
 for a large number of well-commented examples, mostly for running  for a small number of well-commented examples, mostly for running
 GNU/Linux.  GNU/Linux.
   
 The following is an example minimal domain configuration file. The domU  The following is an example minimal domain configuration file. The domU
Line 302  are stored in files and Xen attaches the Line 348  are stored in files and Xen attaches the
 dom0 on domain creation.  The system treats xbd0 as the boot device  dom0 on domain creation.  The system treats xbd0 as the boot device
 without needing explicit configuration.  without needing explicit configuration.
   
 By default, `xl` looks for domain config files in `/usr/pkg/etc/xen`.  Note  There is not type line; that implicitly defines a pv domU.
   
   By convention, domain config files are kept in `/usr/pkg/etc/xen`.  Note
 that "xl create" takes the name of a config file, while other commands  that "xl create" takes the name of a config file, while other commands
 take the name of a domain.  take the name of a domain.
   
 Examples of commands:  Examples of commands:
   
 [[!template id=programlisting text="""  [[!template id=programlisting text="""
 xl create foo  xl create /usr/pkg/etc/xen/foo
 xl console foo  xl console domU-id
 xl create -c foo  xl create -c /usr/pkg/etc/xen/foo
 xl shutdown foo  xl shutdown domU-id
 xl list  xl list
 """]]  """]]
   
Line 321  equivalent to pushing the power button;  Line 369  equivalent to pushing the power button; 
 power-press event and do a clean shutdown.  Shutting down the dom0  power-press event and do a clean shutdown.  Shutting down the dom0
 will trigger controlled shutdowns of all configured domUs.  will trigger controlled shutdowns of all configured domUs.
   
 CPU and memory  ## 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  of CPUs seen by the hypervisor. For a domU, it is controlled
 from the config file by the "vcpus = N" directive.  from the config file by the "vcpus = N" directive.
   
Line 336  than the available memory. Line 383  than the available memory.
 Xen also provides a "balloon" driver, which can be used to let domains  Xen also provides a "balloon" driver, which can be used to let domains
 use more memory temporarily.  use more memory temporarily.
   
 Virtual disks  ## Virtual disks
 -------------  
   
 In domU config files, the disks are defined as a sequence of 3-tuples:  In domU config files, the disks are defined as a sequence of 3-tuples:
   
  * The first element is "method:/path/to/disk". Common methods are   * The first element is "method:/path/to/disk". Common methods are
    "file:" for file-backed vnd, and "phy:" for something that is already     "file:" for a file-backed vnd, and "phy:" for something that is already
    a device.     a device, such as an LVM logical volume.
   
  * The second element is an artifact of how virtual disks are passed to   * The second element is an artifact of how virtual disks are passed to
    Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs     Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
Line 372  Note that NetBSD by default creates only Line 418  Note that NetBSD by default creates only
 than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the  than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
 dom0.  dom0.
   
 Note that NetBSD by default creates only xbd[0123].  If you need more  ## Virtual Networking
 virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.  
   
 Virtual Networking  
 ------------------  
   
 Xen provides virtual Ethernets, each of which connects the dom0 and a  Xen provides virtual Ethernets, each of which connects the dom0 and a
 domU.  For each virtual network, there is an interface "xvifN.M" in  domU.  For each virtual network, there is an interface "xvifN.M" in
Line 408  The MAC address specified is the one use Line 450  The MAC address specified is the one use
 domain.  The interface in dom0 will use this address XOR'd with  domain.  The interface in dom0 will use this address XOR'd with
 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.  00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
   
 Starting domains automatically  ## Starting domains automatically
 ------------------------------  
   
 To start domains `domU-netbsd` and `domU-linux` at boot and shut them  To start domains `domU-netbsd` and `domU-linux` at boot and shut them
 down cleanly on dom0 shutdown, add the following in rc.conf:  down cleanly on dom0 shutdown, add the following in rc.conf:
Line 418  down cleanly on dom0 shutdown, add the f Line 459  down cleanly on dom0 shutdown, add the f
 xendomains="domU-netbsd domU-linux"  xendomains="domU-netbsd domU-linux"
 """]]  """]]
   
 Creating a domU  # domU setup for specific systems
 ===============  
   
 Creating domUs is almost entirely independent of operating system.  We  Creating domUs is almost entirely independent of operating system.  We
 have already presented the basics of config files.  Note that you must  have already presented the basics of config files in the previous system.
 have already completed the dom0 setup so that "xl list" works.  
   Of course, this section presumes that you have a working dom0.
   
 Creating a NetBSD domU  ## Creating a NetBSD PV domU
 ----------------------  
   
 See the earlier config file, and adjust memory.  Decide on how much  See the earlier config file, and adjust memory.  Decide on how much
 storage you will provide, and prepare it (file or lvm).  storage you will provide, and prepare it (file or LVM).
   
 While the kernel will be obtained from the dom0 file system, the same  While the kernel will be obtained from the dom0 file system, the same
 file should be present in the domU as /netbsd so that tools like  file should be present in the domU as /netbsd so that tools like
 savecore(8) can work.   (This is helpful but not necessary.)  savecore(8) can work.   (This is helpful but not necessary.)
   
 The kernel must be specifically for Xen and for use as a domU.  The  The kernel must be specifically built for Xen, to use PV interfacesas
 i386 and amd64 provide the following kernels:  a domU.  NetBSD release builds provide the following kernels:
   
         i386 XEN3PAE_DOMU          i386 XEN3PAE_DOMU
         amd64 XEN3_DOMU          amd64 XEN3_DOMU
   
 This will boot NetBSD, but this is not that useful if the disk is  This will boot NetBSD, but this is not that useful if the disk is
 empty.  One approach is to unpack sets onto the disk outside of xen  empty.  One approach is to unpack sets onto the disk outside of Xen
 (by mounting it, just as you would prepare a physical disk for a  (by mounting it, just as you would prepare a physical disk for a
 system you can't run the installer on).  system you can't run the installer on).
   
Line 452  kernel to / and change the kernel line i Line 492  kernel to / and change the kernel line i
   
         kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"          kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
   
 Then, start the domain as "xl create -c configname".  Then, start the domain as "xl create -c configfile".
   
 Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following  Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
 line should be used in the config file.  line should be used in the config file.
Line 462  line should be used in the config file. Line 502  line should be used in the config file.
 After booting the domain, the option to install via CDROM may be  After booting the domain, the option to install via CDROM may be
 selected.  The CDROM device should be changed to `xbd1d`.  selected.  The CDROM device should be changed to `xbd1d`.
   
 Once done installing, "halt -p" the new domain (don't reboot or halt,  Once done installing, "halt -p" the new domain (don't reboot or halt:
 it would reload the INSTALL_XEN3_DOMU kernel even if you changed the  it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
 config file), switch the config file back to the XEN3_DOMU kernel,  config file), switch the config file back to the XEN3_DOMU kernel,
 and start the new domain again. Now it should be able to use "root on  and start the new domain again. Now it should be able to use "root on
 xbd0a" and you should have a, functional NetBSD domU.  xbd0a" and you should have a functional NetBSD domU.
   
 TODO: check if this is still accurate.  TODO: check if this is still accurate.
 When the new domain is booting you'll see some warnings about *wscons*  When the new domain is booting you'll see some warnings about *wscons*
Line 487  It is also desirable to add Line 527  It is also desirable to add
         powerd=YES          powerd=YES
   
 in rc.conf. This way, the domain will be properly shut down if  in rc.conf. This way, the domain will be properly shut down if
 `xm shutdown -R` or `xm shutdown -H` is used on the dom0.  `xl shutdown -R` or `xl shutdown -H` is used on the dom0.
   \todo Check the translation to xl.
   
 It is not strictly necessary to have a kernel (as /netbsd) in the domU  It is not strictly necessary to have a kernel (as /netbsd) in the domU
 file system.  However, various programs (e.g. netstat) will use that  file system.  However, various programs (e.g. netstat) will use that
Line 497  not really a Xen-specific issue, but bec Line 538  not really a Xen-specific issue, but bec
 obtained from the dom0, it is far more likely to be out of sync or  obtained from the dom0, it is far more likely to be out of sync or
 missing with Xen.)  missing with Xen.)
   
 Creating a Linux domU  Note that NetBSD by default creates only xbd[0123].  If you need more
 ---------------------  virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
   
   ## Creating a Linux domU
   
 Creating unprivileged Linux domains isn't much different from  Creating unprivileged Linux domains isn't much different from
 unprivileged NetBSD domains, but there are some details to know.  unprivileged NetBSD domains, but there are some details to know.
Line 541  To get the Linux console right, you need Line 584  To get the Linux console right, you need
 to your configuration since not all Linux distributions auto-attach a  to your configuration since not all Linux distributions auto-attach a
 tty to the xen console.  tty to the xen console.
   
 Creating a Solaris domU  ## Creating a NetBSD HVM domU
 -----------------------  
   Use type='hmv', probably.  Use a GENERIC kernel within the disk image.
   
   ## Creating a NetBSD PVH domU
   
   Use type='pvh'.
   
   \todo Explain where the kernel comes from.
   
   
   ## Creating a Solaris domU
   
 See possibly outdated  See possibly outdated
 [Solaris domU instructions](/ports/xen/howto-solaris/).  [Solaris domU instructions](/ports/xen/howto-solaris/).
   
   
 PCI passthrough: Using PCI devices in guest domains  ## PCI passthrough: Using PCI devices in guest domains
 ---------------------------------------------------  
   NB: PCI passthrough only works on some Xen versions and as of 2020 it
   is not clear that it works on any version in pkgsrc.  Reports
   confirming or denying this notion should be sent to port-xen@.
   
 The dom0 can give other domains access to selected PCI  The dom0 can give other domains access to selected PCI
 devices. This can allow, for example, a non-privileged domain to have  devices. This can allow, for example, a non-privileged domain to have
Line 618  note that only the "xpci" lines are unus Line 674  note that only the "xpci" lines are unus
         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives          cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
   
   
 NetBSD as a domU in a VPS  # Miscellaneous Information
 =========================  
   ## Nesting under Linux KVM
   
   It is possible to run a Xen and a NetBSD dom0 under Linux KVM.  One
   can enable virtio in the dom0 for greater speed.
   
   ## Other nesting
   
   In theory, any full emulation should be able to run Xen and a NetBSD
   dom0.  The HOWTO does not currently have information about Xen XVM
   mode, nvmm, qemu, Virtualbox, etc.
   
   ## NetBSD 5 as 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  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  hardware.  This section explains how to deal with Xen in a domU as a
Line 646  A second issue is multiple CPUs.  With N Line 719  A second issue is multiple CPUs.  With N
 multiple vcpus, and it is typical for VPS providers to enable multiple  multiple vcpus, and it is typical for VPS providers to enable multiple
 CPUs for NetBSD domUs.  CPUs for NetBSD domUs.
   
 pygrub  ## Complexities due to Xen changes
 -------  
   
 pygrub runs in the dom0 and looks into the domU file system.  This  Xen has many security advisories and people running Xen systems make
 implies that the domU must have a kernel in a file system in a format  different choices.
 known to pygrub.  As of 2014, pygrub seems to be of mostly historical  
 interest.  ### stub domains
   
 pvgrub  Some (Linux only?) dom0 systems use something called "stub domains" to
 ------  isolate qemu from the dom0 system, as a security and reliabilty
   mechanism when running HVM domUs.  Somehow, NetBSD's GENERIC kernel
   ends up using PIO for disks rather than DMA.  Of course, all of this
   is emulated, but emulated PIO is unusably slow.  This problem is not
   currently understood.
   
   ### Grant tables
   
   There are multiple versions of using grant tables, and some security
   advisories have suggested disabling some versions.  Some versions of
   NetBSD apparently only use specific versions and this can lead to
   "NetBSD current doesn't run on hosting provider X" situations.
   
   \todo Explain better.
   
   ## Boot methods
   
   ### pvgrub
   
 pvgrub is a version of grub that uses PV operations instead of BIOS  pvgrub is a version of grub that uses PV operations instead of BIOS
 calls.  It is booted from the dom0 as the domU kernel, and then reads  calls.  It is booted from the dom0 as the domU kernel, and then reads
Line 680  partition for the kernel with the intent Line 769  partition for the kernel with the intent
 which leads to /netbsd not being the actual kernel.  One must remember  which leads to /netbsd not being the actual kernel.  One must remember
 to update the special boot partition.  to update the special boot partition.
   
 Amazon  ### pygrub
 ------  
   
 See the [Amazon EC2 page](/amazon_ec2/).  pygrub runs in the dom0 and looks into the domU file system.  This
   implies that the domU must have a kernel in a file system in a format
   known to pygrub.
   
   pygrub doesn't seem to work to load Linux images under NetBSD dom0,
   and is inherently less secure than pvgrub due to running inside dom0. For both these
   reasons, pygrub should not be used, and is only still present so that
   historical DomU images using it still work.
   
 Random pointers  As of 2014, pygrub seems to be of mostly historical
 ===============  interest. New DomUs should use pvgrub.
   
 This section contains links from elsewhere not yet integrated into the  ## Specific Providers
 HOWTO, and other guides.  
   
 * http://www.lumbercartel.ca/library/xen/  ### Amazon
 * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html  
 * https://gmplib.org/~tege/xen.html  See the [Amazon EC2 page](/amazon_ec2/).

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