Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.141 and 1.153

version 1.141, 2017/12/15 16:40:59 version 1.153, 2018/07/26 12:21:24
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   [[!meta title="Xen HowTo"]]
   
 Introduction  Introduction
 ============  ============
   
 [![[Xen  [![[Xen
 screenshot]](https://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](https://www.netbsd.org/gallery/in-Action/hubertf-xen.png)  screenshot]](https://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](https://www.netbsd.org/gallery/in-Action/hubertf-xen.png)
   
 Xen is a hypervisor (or virtual machine monitor) for x86 hardware  Xen is a hypervisor for x86 hardware, which supports running multiple guest
 (i686-class or higher), which supports running multiple guest  
 operating systems on a single physical machine.  Xen is a Type 1 or  operating systems on a single physical machine.  Xen is a Type 1 or
 bare-metal hypervisor; one uses the Xen kernel to control the CPU,  bare-metal hypervisor; one uses the Xen kernel to control the CPU,
 memory and console, a dom0 operating system which mediates access to  memory and console, a dom0 operating system which mediates access to
 other hardware (e.g., disks, network, USB), and one or more domU  other hardware (e.g., disks, network, USB), and one or more domU
 operating systems which operate in an unprivileged virtualized  operating systems which operate in an unprivileged virtualized
 environment.  IO requests from the domU systems are forwarded by the  environment.  IO requests from the domU systems are forwarded by the
 hypervisor (Xen) to the dom0 to be fulfilled.  Xen hypervisor to the dom0 to be fulfilled.
   
   Xen supports different styles of guest:
   
   [[!table data="""
   Style of guest  |Supported by NetBSD
   PV              |Yes (dom0, domU)
   HVM             |Yes (domU)
   PVHVM           |No
   PVH             |No
   """]]
   
   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.
   
 Xen supports two styles of guests.  The original is Para-Virtualized  
 (PV) which means that the guest OS does not attempt to access hardware  
 directly, but instead makes hypercalls to the hypervisor.  This is  
 analogous to a user-space program making system calls.  (The dom0  
 operating system uses PV calls for some functions, such as updating  
 memory mapping page tables, but has direct hardware access for disk  
 and network.)   PV guests must be specifically coded for Xen.  
   
 The more recent style is HVM, which means that the guest does not have  
 code for Xen and need not be aware that it is running under Xen.  
 Attempts to access hardware registers are trapped and emulated.  This  
 style is less efficient but can run unmodified guests.  
   
 Generally any machine that runs NetBSD/amd64 will work with Xen and PV  
 guests.  In theory i386 computers (without x86_64/amd64 support) can  
 be used for Xen <= 4.2, but we have no recent reports of this working  
 (this is a hint).  For HVM guests, hardware support is needed, but it  
 is common on recent machines.  For Intel CPUs, one needs the VT-x  
 extension, shown in "cpuctl identify 0" as VMX.  For AMD CPUs, one  
 needs the AMD-V extensions, shown in "cpuctl identify 0" as SVM.  
 There are further features for IOMMU virtualization, Intel's VT-d and  There are further features for IOMMU virtualization, Intel's VT-d and
 AMD's AMD-Vi.  TODO: Explain whether Xen on NetBSD makes use of these  AMD's AMD-Vi.  TODO: Explain whether Xen on NetBSD makes use of these
 features.  TODO: Review by someone who really understands this.  features.  TODO: Review by someone who really understands this.
   
 Note that a FreeBSD dom0 requires VT-x and VT-d (or equivalent); this  
 is because the FreeBSD dom0 does not run in PV mode.  
   
 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
 in the dom0 section.)  in the dom0 section.)
   
 NetBSD supports Xen in that it can serve as dom0, be used as a domU,  
 and that Xen kernels and tools are available in pkgsrc.  This HOWTO  
 attempts to address both the case of running a NetBSD dom0 on hardware  
 and running domUs under it (NetBSD and other), and also running NetBSD  
 as a domU in a VPS.  
   
 Xen 3.1 in pkgsrc supports "PCI passthrough", which means that  
 specific PCI devices can be made available to a specific domU instead  
 of the dom0.  This can be useful to let a domU run X11, or access some  
 network interface or other peripheral.  
   
 NetBSD 6 and earlier supported Xen 2; support was removed from NetBSD  
 7.  Xen 2 has been removed from pkgsrc.  
   
 Prerequisites  
 -------------  
   
 Installing NetBSD/Xen is not extremely difficult, but it is more  
 complex than a normal installation of NetBSD.  
 In general, this HOWTO is occasionally overly restrictive about how  
 things must be done, guiding the reader to stay on the established  
 path when there are no known good reasons to stray.  
   
 This HOWTO presumes a basic familiarity with the Xen system  This HOWTO presumes a basic familiarity with the Xen system
 architecture, with installing NetBSD on i386/amd64 hardware, and with  architecture, with installing NetBSD on i386/amd64 hardware, and with
 installing software from pkgsrc.  See also the [Xen  installing software from pkgsrc.  See also the [Xen
 website](http://www.xenproject.org/).  website](http://www.xenproject.org/).
   
   This HOWTO attempts to address both the case of running a NetBSD dom0
   on hardware and running domUs under it (NetBSD and other), and also
   running NetBSD as a domU in a VPS.
   
 Versions of Xen and NetBSD  Versions of Xen and NetBSD
 ==========================  ==========================
   
Line 82  which version to choose.  Versions not i Line 57  which version to choose.  Versions not i
 versions of NetBSD are intentionally ignored.  versions of NetBSD are intentionally ignored.
   
 The term "amd64" is used to refer to both the NetBSD port and to the  The term "amd64" is used to refer to both the NetBSD port and to the
 hardware architecture on which it runs.  (Such hardware is made by  hardware architecture on which it runs.  Such hardware is generally
 both Intel and AMD, and in 2016 a normal PC has this CPU  made by both Intel and AMD, and common on PC computers.
 architecture.)  
   
 Xen  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,
 but note that both packages must be installed together and must have  but note that both packages must be installed together and must have
 matching versions.  matching versions.
   
 xenkernel3 provides Xen 3.1.  It is no longer maintained by Xen, and  Versions available in pkgsrc:
 the last applied security patch was in 2011. Thus, it should not be  
 used.  It supports PCI passthrough, which is why people use it anyway.  
 Xen 3.1 runs on i386 (both non-PAE and PAE) and amd64 hardware.  
   
 xenkernel33 provides Xen 3.3.  It is no longer maintained by Xen, and  
 the last applied security patch was in 2012.  Thus, it should not be  
 used.  Xen 3.3 runs on i386 PAE and amd64 hardware.  There are no good  
 reasons to run this version.  
   
 xenkernel41 provides Xen 4.1.  It is no longer maintained by Xen, but  
 as of 2016-12 received backported security patches.  Xen 4.1 runs on  
 i386 PAE and amd64 hardware.  There are no good reasons to run this  
 version.  
   
 Note that 3.1, 3.3 and 4.1 have been removed from pkgsrc-current, but  
 are in 2016Q4.  They will be removed from this HOWTO sometime after  
 2017Q1.  
   
 xenkernel42 provides Xen 4.2.  It is no longer maintained by Xen, but  
 as of 2016-12 received backported security patches.  Xen 4.2 runs on  
 i386 PAE and amd64 hardware.  The only reason to run this is if you  
 need to use xm instead of xl, or if you need to run on hardware that  
 supports i386 but not amd64.  (This might also be useful if you need  
 an i386 dom0, if it turns out that an amd64 Xen kernel and an i386  
 dom0 is problematic.)  
   
 xenkernel45 provides Xen 4.5.  As of 2016-12, security patches were  
 released by Xen and applied to pkgsrc.  Xen 4.5 runs on amd64 hardware  
 only.  While slightly old, 4.5 has been tested and run by others, so  
 it is the conservative choice.  
   
 xenkernel46 provides Xen 4.6.  It is new to pkgsrc as of 2016-05.  As  
 of 2016-12, security patches were released by Xen and applied to  
 pkgsrc.  Xen 4.6 runs on amd64 hardware only For new installations,  
 4.6 is probably the appropriate choice and it will likely soon be the  
 standard approach.  (If using Ubuntu guests, be sure to have the  
 xentools46 from December, 2016).  
   
 Xen 4.7 (released 2016-06) and 4.8 (released 2016-12) are not yet in  [[!table data="""
 pkgsrc.  Xen Version     |Package Name   |Xen CPU Support        |EOL'ed By Upstream
   4.2             |xenkernel42    |32bit, 64bit           |Yes
   4.5             |xenkernel45    |64bit                  |Yes
   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/).
   
 Note that NetBSD support is called XEN3.  It works with Xen 3 and Xen  Note: Xen 4.2 was the last version to support 32bit CPUs.
 4 because the hypercall interface has been stable.  
   
 Xen command program  Xen command program
 -------------------  -------------------
Line 152  xm and xl work fine.  4.4 is the last ve Line 94  xm and xl work fine.  4.4 is the last ve
 You must make a global choice to use xm or xl, because it affects not  You must make a global choice to use xm or xl, because it affects not
 only which command you use, but the command used by rc.d scripts  only which command you use, but the command used by rc.d scripts
 (specifically xendomains) and which daemons should be run.  The  (specifically xendomains) and which daemons should be run.  The
 xentools packages provide xm for 3.1, 3.3 and 4.1 and xl for 4.2 and up.  xentools packages provide xl for 4.2 and up.
   
 In 4.2, you can choose to use xm by simply changing the ctl_command  In 4.2, you can choose to use xm by simply changing the ctl_command
 variable and setting xend=YES in rc.conf.  variable and setting xend=YES in rc.conf.
Line 165  xbd, where a vnd must be allocated).  Bu Line 107  xbd, where a vnd must be allocated).  Bu
 been adequately tested for a complex custom setup with a large number  been adequately tested for a complex custom setup with a large number
 of interfaces.  of interfaces.
   
 NetBSD  NetBSD versions
 ------  ---------------
   
 The netbsd-6, netbsd-7, and -current branches are all reasonable  The netbsd-7, netbsd-8, and -current branches are all reasonable
 choices, with more or less the same considerations for non-Xen use.  choices, with more or less the same considerations for non-Xen use.
 Therefore, netbsd-7 is recommended as the stable version of the most  NetBSD 8 is recommended as the stable version of the most recent
 recent release for production use.  In addition, netbsd-7 and -current  release for production use.
 have a important scheduler fix (in November of 2015) affecting  
 contention between dom0 and domUs; see  For developing Xen, netbsd-current may be appropriate.
 https://releng.netbsd.org/cgi-bin/req-7.cgi?show=1040 for a  
 description.  For those wanting to learn Xen or without production  
 stability concerns, netbsd-7 is still likely most appropriate, but  
 -current is also a reasonable choice.  (Xen runs ok on netbsd-5, but  
 the xentools packages are likely difficult to build, and netbsd-5 is  
 not supported.)  
   
 As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is  As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
 no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really  no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
 need SMP for dom0 functions; the lack of support is really a problem  need SMP for dom0 functions; the lack of support is really a problem
 when using a dom0 as a normal computer.)  when using a dom0 as a normal computer.)
   
   Note: NetBSD support is called XEN3. However, it does support Xen 4,
   because the hypercall interface has remained identical.
   
 Architecture  Architecture
 ------------  ------------
   
 Xen itself can run on i386 (Xen < 4.2) or amd64 hardware (all Xen  Xen itself can run on i386 (Xen < 4.2) or amd64 hardware (all Xen
 versions).  (Practically, almost any computer where one would want to  versions).  Practically, almost any computer where one would want to
 run Xen today supports amd64.)  run Xen today supports amd64.
   
 Xen, the dom0 system, and each domU system can be either i386 or  Xen, the dom0 system, and each domU system can be either i386 or
 amd64.  When building a xenkernel package, one obtains an i386 Xen  amd64.  When building a xenkernel package, one obtains an i386 Xen
Line 201  be i386.  With an amd64 Xen kernel, an a Line 140  be i386.  With an amd64 Xen kernel, an a
 work, and an i386 dom0 kernel should in theory work.  An amd64  work, and an i386 dom0 kernel should in theory work.  An amd64
 Xen/dom0 is known to support both i386 and amd64 domUs.  Xen/dom0 is known to support both i386 and amd64 domUs.
   
 i386 dom0 and domU kernels must be PAE (except for an i386 Xen 3.1  i386 dom0 and domU kernels must be PAE. PAE kernels are included in
 kernel, where one can use non-PAE for dom0 and all domUs); PAE kernels  the NetBSD default build.
 are included in the NetBSD default build.  (Note that emacs (at least)  
 fails if run on i386 with PAE when built without, and vice versa,  
 presumably due to bugs in the undump code.)  
   
 Because of the above, the standard approach is to use an amd64 Xen  Because of the above, the standard approach is to use an amd64 Xen
 kernel and NetBSD/amd64 for the dom0.  For domUs, NetBSD/i386 (with  kernel and NetBSD/amd64 for the dom0.  For domUs, NetBSD/i386 (with
Line 227  caution that the total situation is comp Line 163  caution that the total situation is comp
 understood. On top of that caution, the post is about Linux, not  understood. On top of that caution, the post is about Linux, not
 NetBSD.  TODO: Include link to benchmarks, if someone posts them.  NetBSD.  TODO: Include link to benchmarks, if someone posts them.
   
 Stability  
 ---------  
   
 Mostly, NetBSD as a dom0 or domU is quite stable.  
 However, there are some open PRs indicating problems.  
   
  - [PR 48125](http://gnats.netbsd.org/48125)  
   
 Note also that there are issues with sparse vnd(4) instances, but  
 these are not about Xen -- they just are noticed with sparse vnd(4)  
 instances in support of virtual disks in a dom0.  
   
 Recommendation  
 --------------  
   
 Therefore, this HOWTO recommends running xenkernel45 or xenkernel46,  
 xl, the NetBSD 7 stable branch, and to use an amd64 kernel as the  
 dom0.  Either the i386PAE or amd64 version of NetBSD may be used as  
 domUs.  
   
 Because bugs are fixed quite often, and because of Xen security  
 advisories, it is good to stay up to date with NetBSD (tracking a  
 stable branch), with the Xen kernel (tracking a Xen version via  
 pkgsrc), and with the Xen tools.  Specifically, NetBSD (-7 and  
 -current) got an important fix affecting dom0/domU timesharing in  
 November, 2015, and xentools46 got a fix to enable Ubuntu guests to  
 boot in December, 2016.  
   
 Status  
 ------  
   
 Ideally, all versions of Xen in pkgsrc would build on all supported  
 versions of NetBSD/amd64, to the point where this section would be  
 silly.  However, that has not always been the case.  Besides aging  
 code and aging compilers, qemu (included in xentools for HVM support)  
 is difficult to build.  Note that there is intentionally no data for  
 4.5+ up for i386, and often omits xentools info if the corresponding  
 kernel fails.  
   
 The following table gives status, with the date last checked  
 (generally on the most recent quarterly branch).  The first code is  
 "builds" if it builds ok, and "FAIL" for a failure to build.  The  
 second code/date only appears for xenkernel* and is "works" if it runs  
 ok as a dom0 and can support a domU, and "FAIL" if it won't boot or  
 run a domU.  
   
         xenkernel3 netbsd-6 i386 FAIL 201612  
         xenkernel33 netbsd-6 i386 FAIL 201612  
         xenkernel41 netbsd-6 i386 builds 201612  
         xenkernel42 netbsd-6 i386 builds 201612  
         xentools3 netbsd-6 i386 FAIL 201612  
         xentools33 netbsd-6 i386 FAIL 201612  
         xentools41 netbsd-6 i386 builds 201612  
         xentools42 netbsd-6 i386 FAIL 201612  
   
         xenkernel3 netbsd-7 i386 FAIL 201412  
         xenkernel33 netbsd-7 i386 FAIL 201412  
         xenkernel41 netbsd-7 i386 builds 201412  
         xenkernel42 netbsd-7 i386 builds 201412  
         xentools41 netbsd-7 i386 builds 201412  
         xentools42 netbsd-7 i386 ??FAIL 201412  
   
         xenkernel3 netbsd-6 amd64 FAIL 201612  
         xenkernel33 netbsd-6 amd64 FAIL 201612  
         xenkernel41 netbsd-6 amd64 builds 201612 works 201612  
         xenkernel42 netbsd-6 amd64 builds 201612 works 201612  
         xenkernel45 netbsd-6 amd64 builds 201612  
         xenkernel46 netbsd-6 amd64 builds 201612  
         xentools41 netbsd-6 amd64 builds 201612  
         xentools42 netbsd-6 amd64 builds 201612  
         xentools45 netbsd-6 amd64 builds 201612  
         xentools46 netbsd-6 amd64 FAIL 201612  
   
         xenkernel3 netbsd-7 amd64 builds 201612  
         xenkernel33 netbsd-7 amd64 builds 201612  
         xenkernel41 netbsd-7 amd64 builds 201612  
         xenkernel42 netbsd-7 amd64 builds 201612  
         xenkernel45 netbsd-7 amd64 builds 201612  
         xenkernel46 netbsd-7 amd64 builds 201612  
         xentools3 netbsd-7 amd64 builds 201612  
         xentools3-hvm netbsd-7 amd64 builds 201612  
         xentools33 netbsd-7 amd64 FAIL 201612  
         xentools41 netbsd-7 amd64 builds 201612  
         xentools42 netbsd-7 amd64 builds 201612  
         xentools45 netbsd-7 amd64 builds 201612  
         xentools46 netbsd-7 amd64 builds 201612  
   
 NetBSD as a dom0  NetBSD as a dom0
 ================  ================
   
Line 332  half-dozen domUs of 512M and 32G each.   Line 181  half-dozen domUs of 512M and 32G each.  
 have to be bigger than the sum of the RAM/disk needs of the dom0 and  have to be bigger than the sum of the RAM/disk needs of the dom0 and
 all the domUs.  all the domUs.
   
   In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
   512M it worked reliably.  This does not make sense, but if you see
   "not ELF" after Xen boots, try increasing dom0 RAM.
   
 Styles of dom0 operation  Styles of dom0 operation
 ------------------------  ------------------------
   
Line 400  documentation](https://www.NetBSD.org/do Line 253  documentation](https://www.NetBSD.org/do
 pkgsrc.  Ensure that your packages are recent; the HOWTO does not  pkgsrc.  Ensure that your packages are recent; the HOWTO does not
 contemplate old builds.  contemplate old builds.
   
   
 For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More  
 recent versions have HVM support integrated in the main xentools  
 package.  It is entirely reasonable to run only PV guests.  
   
 Next you need to install the selected Xen kernel itself, which is  Next you need to install the selected Xen kernel itself, which is
 installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.  installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
 For debugging, one may copy xen-debug.gz; this is conceptually similar  For debugging, one may copy xen-debug.gz; this is conceptually similar
Line 412  to DIAGNOSTIC and DEBUG in NetBSD.  xen- Line 260  to DIAGNOSTIC and DEBUG in NetBSD.  xen-
 useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel  useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
 in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz  in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
 of a NetBSD build.  If using i386, use  of a NetBSD build.  If using i386, use
 releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  (If using Xen  releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  Both xen and
 3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen.  But you  the NetBSD kernel may be (and typically are) left compressed.
 should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and  
 typically are) left compressed.  
   
 In a dom0, kernfs is mandatory for xend to communicate with the  In a dom0, kernfs is mandatory for xend to communicate with the
 kernel, so ensure that /kern is in fstab.  (A standard NetBSD install  kernel, so ensure that /kern is in fstab.  (A standard NetBSD install
Line 426  with an MBR bootblock, either bootxx_ffs Line 272  with an MBR bootblock, either bootxx_ffs
 beginning of your root file system, have /boot, and likely also  beginning of your root file system, have /boot, and likely also
 /boot.cfg.  (If not, fix before continuing!)  /boot.cfg.  (If not, fix before continuing!)
   
 Add a line to to /boot.cfg to boot Xen.  See boot.cfg(5) for an  Add a line to /boot.cfg to boot Xen.  See boot.cfg(5) for an
 example.  The basic line is  example.  The basic line is:
   
         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M  [[!template id=programlisting text="""
   menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
   """]]
   
 which specifies that the dom0 should have 256M, leaving the rest to be  which specifies that the dom0 should have 512M, leaving the rest to be
 allocated for domUs.  To use a serial console, use  allocated for domUs.  To use a serial console, use
   
         menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=256M console=com1 com1=9600,8n1  [[!template id=programlisting text="""
   menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
   """]]
   
 which will use the first serial port for Xen (which counts starting  which will use the first serial port for Xen (which counts starting
 from 1, unlike NetBSD which counts starting from 0), forcing  from 1, unlike NetBSD which counts starting from 0), forcing
Line 443  speed/parity.  Because the NetBSD comman Line 293  speed/parity.  Because the NetBSD comman
 which directs the console I/O through Xen to the same console device Xen  which directs the console I/O through Xen to the same console device Xen
 itself uses (in this case, the serial port).  itself uses (in this case, the serial port).
   
 In an attempt to add performance, one can also add  In an attempt to add performance, one can also add:
   
         dom0_max_vcpus=1 dom0_vcpus_pin  [[!template id=programlisting text="""
   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.  TODO: benchmark this.  more) and to pin that vcpu to a physical CPU.  TODO: benchmark this.
Line 462  sure /netbsd is ok).  Consider also a li Line 314  sure /netbsd is ok).  Consider also a li
 of Xen and the dom0 kernel, but note that non-Xen NetBSD can be used  of Xen and the dom0 kernel, but note that non-Xen NetBSD can be used
 to resolve Xen booting issues.  to resolve Xen booting issues.
   
 Probably you want a default=N line to choose Xen in the absence of  
 intervention.  
   
 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.
   
Line 485  described above.) Line 334  described above.)
 Configuring Xen  Configuring Xen
 ---------------  ---------------
   
 Xen logs will be in /var/log/xen.  
   
 Now, you have a system that will boot Xen and the dom0 kernel, but not  Now, you have a system that will boot Xen and the dom0 kernel, but not
 do anything else special.  Make sure that you have rebooted into Xen.  do anything else special.  Make sure that you have rebooted into Xen.
 There will be no domUs, and none can be started because you still have  There will be no domUs, and none can be started because you still have
 to configure the dom0 daemons.  to configure the dom0 daemons.
   
 The daemons which should be run vary with Xen version and with whether  The daemons which should be run vary with Xen version and with whether
 one is using xm or xl.  The Xen 3.1, 3.3 and 4.1 packages use xm.  Xen  one is using xm or xl. Xen 4.2 and up packages use xl. To use xm with 4.2,
 4.2 and up packages use xl.  To use xm with 4.2, edit xendomains to  edit xendomains to use xm instead.
 use xm instead.  
   
 For 3.1 and 3.3, you should enable xend and xenbackendd:  
   
         xend=YES  
         xenbackendd=YES  
   
 For 4.1 and up, you should enable xencommons.  Not enabling xencommons  For 4.1 and up, you should enable xencommons.  Not enabling xencommons
 will result in a hang; it is necessary to hit ^C on the console to let  will result in a hang; it is necessary to hit ^C on the console to let
 the machine finish booting.  If you are using xm (default in 4.1, or  the machine finish booting.  If you are using xm (default in 4.1, or
 if you changed xendomains in 4.2), you should also enable xend:  if you changed xendomains in 4.2), you should also enable xend:
   
         xend=YES # only if using xm, and only installed <= 4.2  [[!template id=programlisting text="""
         xencommons=YES  xend=YES # only if using xm, and only installed <= 4.2
   xencommons=YES
   """]]
   
 TODO: Recommend for/against xen-watchdog.  TODO: Recommend for/against xen-watchdog.
   
Line 516  After you have configured the daemons an Line 359  After you have configured the daemons an
 order given) or rebooted, use xm or xl to inspect Xen's boot messages,  order given) or rebooted, use xm or xl to inspect Xen's boot messages,
 available resources, and running domains.  An example with xl follows:  available resources, and running domains.  An example with xl follows:
   
         # xl dmesg  [[!template id=programlisting text="""
         [xen's boot info]  # xl dmesg
         # xl info  ... xen's boot info ...
         [available memory, etc.]  # xl info
         # xl list  ... available memory, etc ...
         Name              Id  Mem(MB)  CPU  State  Time(s)  Console  # xl list
         Domain-0           0       64    0  r----     58.1  Name              Id  Mem(MB)  CPU  State  Time(s)  Console
   Domain-0           0       64    0  r----     58.1
   """]]
   
   Xen logs will be in /var/log/xen.
   
 ### Issues with xencommons  ### Issues with xencommons
   
Line 541  this will get fixed any time soon. Line 388  this will get fixed any time soon.
 The installation of NetBSD should already have created devices for xen  The installation of NetBSD should already have created devices for xen
 (xencons, xenevt, xsd_kva), but if they are not present, create them:  (xencons, xenevt, xsd_kva), but if they are not present, create them:
   
         cd /dev && sh MAKEDEV xen  [[!template id=programlisting text="""
   cd /dev && sh MAKEDEV xen
   """]]
   
 anita (for testing NetBSD)  anita (for testing NetBSD)
 --------------------------  --------------------------
Line 550  With the setup so far (assuming 4.2/xl), Line 399  With the setup so far (assuming 4.2/xl),
 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):
   
         anita --vmm=xl test file:///usr/obj/i386/  [[!template id=programlisting text="""
   anita --vmm=xl test file:///usr/obj/i386/
   """]]
   
 Alternatively, one can use --vmm=xm to use xm-based domU creation  Alternatively, one can use --vmm=xm to use xm-based domU creation
 instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.  instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.
Line 602  section. Line 453  section.
         # Install secondary boot loader          # Install secondary boot loader
         cp -p /usr/mdec/boot /          cp -p /usr/mdec/boot /
         # Create boot.cfg following earlier guidance:          # Create boot.cfg following earlier guidance:
         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M          menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M          menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
         menu=GENERIC:boot          menu=GENERIC:boot
         menu=GENERIC single-user:boot -s          menu=GENERIC single-user:boot -s
         menu=GENERIC.ok:boot netbsd.ok          menu=GENERIC.ok:boot netbsd.ok
Line 639  Specifically, for 4.x remove autorestart Line 490  Specifically, for 4.x remove autorestart
 are specified with numbers as the second argument, as the examples  are specified with numbers as the second argument, as the examples
 above show, and not NetBSD device names.  above show, and not NetBSD device names.
   
 Hardware known to work  
 ----------------------  
   
 Arguably, this section is misplaced, and there should be a page of  
 hardware that runs NetBSD/amd64 well, with the mostly-well-founded  
 assumption that NetBSD/xen runs fine on any modern hardware that  
 NetBSD/amd64 runs well on.  Until then, we give motherboard/CPU (and  
 sometimes RAM) pairs/triples to aid those choosing a motherboard.  
 Note that Xen systems usually do not run X, so a listing here does not  
 imply that X works at all.  
   
         Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC  
         Supermicro ??, Atom C2758 (8 core), 32 GiB ECC  
         ASUS M5A78L-M/USB3 AM3+ microATX, AMD Piledriver X8 4000MHz, 16 GiB ECC  
   
 Older hardware:  
   
         Intel D915GEV, Pentium4 CPU 3.40GHz, 4GB 533MHz Synchronous DDR2  
         INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU     E6850  @ 3.00GHz"  
         INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU     E8400  @ 3.00GHz"  
   
 Running Xen under qemu  
 ----------------------  
   
 The astute reader will note that this section is somewhat twisted.  
 However, it can be useful to run Xen under qemu either because the  
 version of NetBSD as a dom0 does not run on the hardware in use, or to  
 generate automated test cases involving Xen.  
   
 In 2015-01, the following combination was reported to mostly work:  
   
         host OS: NetBSD/amd64 6.1.4  
         qemu: 2.2.0 from pkgsrc  
         Xen kernel: xenkernel42-4.2.5nb1 from pkgsrc  
         dom0 kernel: NetBSD/amd64 6.1.5  
         Xen tools: xentools42-4.2.5 from pkgsrc  
   
 See [PR 47720](https://gnats.netbsd.org/47720) for a problem with dom0  
 shutdown.  
   
 Unprivileged domains (domU)  Unprivileged domains (domU)
 ===========================  ===========================
   
Line 872  Sizing domains Line 683  Sizing domains
   
 Modern x86 hardware has vast amounts of resources.  However, many  Modern x86 hardware has vast amounts of resources.  However, many
 virtual servers can function just fine on far less.  A system with  virtual servers can function just fine on far less.  A system with
 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is  512M of RAM and a 4G disk can be a reasonable choice.  Note that it is
 far easier to adjust virtual resources than physical ones.  For  far easier to adjust virtual resources than physical ones.  For
 memory, it's just a config file edit and a reboot.  For disk, one can  memory, it's just a config file edit and a reboot.  For disk, one can
 create a new file and vnconfig it (or lvm), and then dump/restore,  create a new file and vnconfig it (or lvm), and then dump/restore,
Line 1160  to update the special boot partition. Line 971  to update the special boot partition.
 Amazon  Amazon
 ------  ------
   
 See the [Amazon EC2 page](../amazon_ec2/).  See the [Amazon EC2 page](/amazon_ec2/).
   
 Using npf  
 ---------  
   
 In standard kernels, npf is a module, and thus cannot be loaded in a  
 DOMU kernel.  
   
 TODO: Explain how to compile npf into a custom kernel, answering (but  
 note that the problem was caused by not booting the right kernel)  
 [this email to  
 netbsd-users](https://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html).  
   
 TODO items for improving NetBSD/xen  TODO items for improving NetBSD/xen
 ===================================  ===================================
Line 1191  TODO items for improving NetBSD/xen Line 991  TODO items for improving NetBSD/xen
   * Get UFS2 patches into pvgrub.    * Get UFS2 patches into pvgrub.
 * Add support for PV ops to a version of /boot, and make it usable as  * Add support for PV ops to a version of /boot, and make it usable as
   a kernel in Xen, similar to pvgrub.    a kernel in Xen, similar to pvgrub.
 * Solve somehow the issue with modules for GENERIC not being loadable  
   in a Xen dom0 or domU kernel.  
   
 Random pointers  Random pointers
 ===============  ===============

Removed from v.1.141  
changed lines
  Added in v.1.153


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