Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.164 and 1.180

version 1.164, 2019/04/11 17:31:14 version 1.180, 2020/11/15 14:31:58
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:  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="""  [[!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  
 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.
   
   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.
   
 At boot, the dom0 kernel is loaded as a module with Xen as the kernel.  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  The dom0 can start one or more domUs.  (Booting is explained in detail
Line 35  website](http://www.xenproject.org/). Line 48  website](http://www.xenproject.org/).
   
 [[!toc]]  [[!toc]]
   
 #Versions and Support  # Versions and Support
   
 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 45  matching versions. Line 58  matching versions.
 Versions available in pkgsrc:  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        |xm?    |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/).
Line 63  dom0  |No Line 73  dom0  |No
 domU            |Yes  domU            |Yes
 """]]  """]]
   
 Note: NetBSD support is called XEN3. However, it does support Xen 4,  Note: NetBSD support is called XEN3.  However, it does support Xen 4,
 because the hypercall interface has remained identical.  because the hypercall interface has remained identical.
   
   Older Xen had a python-based management tool called xm, now replaced
   by xl.
   
 Architecture  Architecture
 ------------  ------------
   
 Xen itself runs on x86_64 hardware.  Xen 4.5 and later runs on x86_64 hardware (the NetBSD amd64 port).
   There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD.
 The dom0 system, plus each domU, can be either i386PAE or amd64.  
 i386 without PAE is not supported.  
   
 The standard approach is to use NetBSD/amd64 for the dom0.  
   
 To use an i386PAE dom0, one must build or obtain a 64bit Xen kernel and  The dom0 system should be amd64.  (Instructions for i386PAE dom0 have been removed from the HOWTO.)
 install it on the system.  
   
 For domUs, i386PAE is considered as  The domU can be i386PAE or amd64.
 [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)  i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64.
 than amd64.  
   
 #Creating a dom0  # Creating a 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 102  just as you would if you were not using  Line 109  just as you would if you were not using 
 Installation of Xen  Installation of Xen
 -------------------  -------------------
   
 We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as  We will consider that you chose to use Xen 4.13, with NetBSD/amd64 as
 dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.  dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
   
 Once this is done, install the Xen kernel itself:  Once this is done, install the Xen kernel itself:
Line 142  itself uses (in this case, the serial po Line 149  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.
   
Line 193  this will get fixed any time soon. Line 200  this will get fixed any time soon.
 anita (for testing NetBSD)  anita (for testing NetBSD)
 --------------------------  --------------------------
   
 With the setup so far (assuming 4.8/xl), one should be able to run  With the setup so far, one should be able to run
 anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as  anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
 root, because anita must create a domU):  root, because anita must create a domU):
   
Line 283  the dom0.  NetBSD's /dev/random system w Line 290  the dom0.  NetBSD's /dev/random system w
 Config files  Config files
 ------------  ------------
   
 See /usr/pkg/share/examples/xen/xlexample*,  See /usr/pkg/share/examples/xen/xlexample*
 for a small number of well-commented examples, mostly for running  for a small number of well-commented examples, mostly for running
 GNU/Linux.  GNU/Linux.
   
Line 330  will trigger controlled shutdowns of all Line 337  will trigger controlled shutdowns of all
 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 424  down cleanly on dom0 shutdown, add the f Line 431  down cleanly on dom0 shutdown, add the f
 xendomains="domU-netbsd domU-linux"  xendomains="domU-netbsd domU-linux"
 """]]  """]]
   
 #Creating a domU  # Creating a domU
   
 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.  Note that you must
 have already completed the dom0 setup so that "xl list" works.  have already completed the dom0 setup so that "xl list" works.
   
 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).
Line 546  To get the Linux console right, you need Line 553  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 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  Creating a Solaris domU
 -----------------------  -----------------------
   
Line 556  See possibly outdated Line 574  See possibly outdated
 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
 access to a physical network interface or disk controller.  However,  access to a physical network interface or disk controller.  However,
Line 623  note that only the "xpci" lines are unus Line 645  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  # 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  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 650  A second issue is multiple CPUs.  With N Line 679  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
   
   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.
   
 pvgrub  pvgrub
 ------  ------
Line 684  partition for the kernel with the intent Line 728  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.
   
   pygrub
   -------
   
   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.
   
   As of 2014, pygrub seems to be of mostly historical
   interest. New DomUs should use pvgrub.
   
 Amazon  Amazon
 ------  ------
   

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