Annotation of wikisrc/ports/xen/howto.mdwn, revision 1.152

1.144     maxv        1: [[!meta title="Xen HowTo"]]
                      2: 
1.5       mspo        3: Introduction
1.13      gdt         4: ============
1.1       mspo        5: 
                      6: [![[Xen
1.140     khorben     7: screenshot]](https://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](https://www.netbsd.org/gallery/in-Action/hubertf-xen.png)
1.1       mspo        8: 
1.149     maxv        9: Xen is a hypervisor for x86 hardware, which supports running multiple guest
1.58      gdt        10: operating systems on a single physical machine.  Xen is a Type 1 or
                     11: bare-metal hypervisor; one uses the Xen kernel to control the CPU,
                     12: memory and console, a dom0 operating system which mediates access to
                     13: other hardware (e.g., disks, network, USB), and one or more domU
                     14: operating systems which operate in an unprivileged virtualized
                     15: environment.  IO requests from the domU systems are forwarded by the
1.149     maxv       16: Xen hypervisor to the dom0 to be fulfilled.
1.12      gdt        17: 
1.149     maxv       18: Xen supports different styles of guest:
                     19: 
                     20: [[!table data="""
                     21: Style of guest |Supported by NetBSD
1.150     maxv       22: PV             |Yes (dom0, domU)
                     23: HVM            |Yes (domU)
1.149     maxv       24: PVHVM          |No
                     25: PVH            |No
                     26: """]]
                     27: 
                     28: In Para-Virtualized (PV) mode, the guest OS does not attempt to access
                     29: hardware directly, but instead makes hypercalls to the hypervisor; PV
                     30: guests must be specifically coded for Xen. In HVM mode, no guest
                     31: modification is required; however, hardware support is required, such
                     32: as VT-x on Intel CPUs and SVM on AMD CPUs.
                     33: 
                     34: There are further features for IOMMU virtualization, Intel's VT-d and
                     35: AMD's AMD-Vi.  TODO: Explain whether Xen on NetBSD makes use of these
                     36: features.  TODO: Review by someone who really understands this.
1.12      gdt        37: 
1.27      jnemeth    38: At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
1.12      gdt        39: The dom0 can start one or more domUs.  (Booting is explained in detail
                     40: in the dom0 section.)
                     41: 
                     42: This HOWTO presumes a basic familiarity with the Xen system
1.123     gdt        43: architecture, with installing NetBSD on i386/amd64 hardware, and with
                     44: installing software from pkgsrc.  See also the [Xen
                     45: website](http://www.xenproject.org/).
1.1       mspo       46: 
1.150     maxv       47: This HOWTO attempts to address both the case of running a NetBSD dom0
                     48: on hardware and running domUs under it (NetBSD and other), and also
                     49: running NetBSD as a domU in a VPS.
                     50: 
1.15      gdt        51: Versions of Xen and NetBSD
                     52: ==========================
                     53: 
1.27      jnemeth    54: Most of the installation concepts and instructions are independent
                     55: of Xen version and NetBSD version.  This section gives advice on
                     56: which version to choose.  Versions not in pkgsrc and older unsupported
                     57: versions of NetBSD are intentionally ignored.
1.15      gdt        58: 
1.133     gdt        59: The term "amd64" is used to refer to both the NetBSD port and to the
1.150     maxv       60: hardware architecture on which it runs.  Such hardware is generally
                     61: made by both Intel and AMD, and common on PC computers.
1.133     gdt        62: 
1.146     maxv       63: Xen versions
                     64: ------------
1.15      gdt        65: 
1.111     wiz        66: In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages
1.15      gdt        67: xenkernel and xentools.  We will refer only to the kernel versions,
                     68: but note that both packages must be installed together and must have
                     69: matching versions.
                     70: 
1.145     maxv       71: Versions available in pkgsrc:
1.85      gdt        72: 
1.145     maxv       73: [[!table data="""
                     74: Xen Version    |Package Name   |Xen CPU Support        |EOL'ed By Upstream
                     75: 4.2            |xenkernel42    |32bit, 64bit           |Yes
                     76: 4.5            |xenkernel45    |64bit                  |Yes
                     77: 4.6            |xenkernel46    |64bit                  |Partially
                     78: 4.8            |xenkernel48    |64bit                  |No
                     79: 4.11           |xenkernel411   |64bit                  |No
                     80: """]]
1.113     gdt        81: 
1.96      gdt        82: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
                     83: 
1.145     maxv       84: Note: Xen 4.2 was the last version to support 32bit CPUs.
                     85: 
1.19      gdt        86: Xen command program
                     87: -------------------
                     88: 
1.79      gdt        89: Early Xen used a program called xm to manipulate the system from the
1.19      gdt        90: dom0.  Starting in 4.1, a replacement program with similar behavior
1.79      gdt        91: called xl is provided, but it does not work well in 4.1.  In 4.2, both
1.127     gdt        92: xm and xl work fine.  4.4 is the last version that has xm.
                     93: 
                     94: You must make a global choice to use xm or xl, because it affects not
                     95: only which command you use, but the command used by rc.d scripts
                     96: (specifically xendomains) and which daemons should be run.  The
1.146     maxv       97: xentools packages provide xl for 4.2 and up.
1.127     gdt        98: 
                     99: In 4.2, you can choose to use xm by simply changing the ctl_command
1.135     gdt       100: variable and setting xend=YES in rc.conf.
1.127     gdt       101: 
                    102: With xl, virtual devices are configured in parallel, which can cause
                    103: problems if they are written assuming serial operation (e.g., updating
1.130     gdt       104: firewall rules without explicit locking).  There is now locking for
                    105: the provided scripts, which works for normal casses (e.g, file-backed
                    106: xbd, where a vnd must be allocated).  But, as of 201612, it has not
                    107: been adequately tested for a complex custom setup with a large number
                    108: of interfaces.
1.19      gdt       109: 
1.147     maxv      110: NetBSD versions
                    111: ---------------
1.15      gdt       112: 
1.142     gdt       113: The netbsd-7, netbsd-8, and -current branches are all reasonable
1.105     gdt       114: choices, with more or less the same considerations for non-Xen use.
1.147     maxv      115: NetBSD 8 is recommended as the stable version of the most recent
                    116: release for production use.
1.146     maxv      117: 
                    118: For developing Xen, netbsd-current may be appropriate.
1.15      gdt       119: 
                    120: As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
                    121: no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
1.105     gdt       122: need SMP for dom0 functions; the lack of support is really a problem
                    123: when using a dom0 as a normal computer.)
1.15      gdt       124: 
1.147     maxv      125: Note: NetBSD support is called XEN3. However, it does support Xen 4,
                    126: because the hypercall interface has remained identical.
                    127: 
1.18      gdt       128: Architecture
                    129: ------------
                    130: 
1.133     gdt       131: Xen itself can run on i386 (Xen < 4.2) or amd64 hardware (all Xen
1.151     maxv      132: versions).  Practically, almost any computer where one would want to
                    133: run Xen today supports amd64.
1.99      gdt       134: 
1.133     gdt       135: Xen, the dom0 system, and each domU system can be either i386 or
                    136: amd64.  When building a xenkernel package, one obtains an i386 Xen
1.134     wiz       137: kernel on an i386 host, and an amd64 Xen kernel on an amd64 host.  If
1.133     gdt       138: the Xen kernel is i386, then the dom0 kernel and all domU kernels must
                    139: be i386.  With an amd64 Xen kernel, an amd64 dom0 kernel is known to
                    140: work, and an i386 dom0 kernel should in theory work.  An amd64
                    141: Xen/dom0 is known to support both i386 and amd64 domUs.
                    142: 
1.151     maxv      143: i386 dom0 and domU kernels must be PAE. PAE kernels are included in
                    144: the NetBSD default build.
1.135     gdt       145: 
                    146: Because of the above, the standard approach is to use an amd64 Xen
                    147: kernel and NetBSD/amd64 for the dom0.  For domUs, NetBSD/i386 (with
                    148: the PAE kernel) and NetBSD/amd64 are in widespread use, and there is
                    149: little to no Xen-specific reason to prefer one over the other.
1.133     gdt       150: 
                    151: Note that to use an i386 dom0 with Xen 4.5 or higher, one must build
1.135     gdt       152: (or obtain from pre-built packages) an amd64 Xen kernel and install
                    153: that on the system.  (One must also use a PAE i386 kernel, but this is
                    154: also required with an i386 Xen kernel.).  Almost no one in the
                    155: NetBSD/Xen community does this, and the standard, well-tested,
                    156: approach is to use an amd64 dom0.
                    157: 
                    158: A [posting on
                    159: xen-devel](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
                    160: explained that PV system call overhead was higher on amd64, and thus
                    161: there is some notion that i386 guests are faster.  It goes on to
                    162: caution that the total situation is complex and not entirely
                    163: understood. On top of that caution, the post is about Linux, not
                    164: NetBSD.  TODO: Include link to benchmarks, if someone posts them.
1.29      gdt       165: 
1.15      gdt       166: NetBSD as a dom0
                    167: ================
                    168: 
                    169: NetBSD can be used as a dom0 and works very well.  The following
                    170: sections address installation, updating NetBSD, and updating Xen.
1.19      gdt       171: Note that it doesn't make sense to talk about installing a dom0 OS
                    172: without also installing Xen itself.  We first address installing
                    173: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
                    174: NetBSD install to a dom0 install by just changing the kernel and boot
                    175: configuration.
1.15      gdt       176: 
1.45      gdt       177: For experimenting with Xen, a machine with as little as 1G of RAM and
                    178: 100G of disk can work.  For running many domUs in productions, far
1.135     gdt       179: more will be needed; e.g. 4-8G and 1T of disk is reasonable for a
                    180: half-dozen domUs of 512M and 32G each.  Basically, the RAM and disk
                    181: have to be bigger than the sum of the RAM/disk needs of the dom0 and
                    182: all the domUs.
1.45      gdt       183: 
1.142     gdt       184: In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with
                    185: 512M it worked reliably.  This does not make sense, but if you see
                    186: "not ELF" after Xen boots, try increasing dom0 RAM.
                    187: 
1.15      gdt       188: Styles of dom0 operation
                    189: ------------------------
                    190: 
                    191: There are two basic ways to use Xen.  The traditional method is for
                    192: the dom0 to do absolutely nothing other than providing support to some
                    193: number of domUs.  Such a system was probably installed for the sole
                    194: purpose of hosting domUs, and sits in a server room on a UPS.
                    195: 
                    196: The other way is to put Xen under a normal-usage computer, so that the
                    197: dom0 is what the computer would have been without Xen, perhaps a
                    198: desktop or laptop.  Then, one can run domUs at will.  Purists will
                    199: deride this as less secure than the previous approach, and for a
                    200: computer whose purpose is to run domUs, they are right.  But Xen and a
1.93      gdt       201: dom0 (without domUs) is not meaningfully less secure than the same
1.15      gdt       202: things running without Xen.  One can boot Xen or boot regular NetBSD
                    203: alternately with little problems, simply refraining from starting the
                    204: Xen daemons when not running Xen.
                    205: 
                    206: Note that NetBSD as dom0 does not support multiple CPUs.  This will
1.51      gdt       207: limit the performance of the Xen/dom0 workstation approach.  In theory
                    208: the only issue is that the "backend drivers" are not yet MPSAFE:
1.140     khorben   209:   https://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html
1.15      gdt       210: 
1.19      gdt       211: Installation of NetBSD
                    212: ----------------------
1.13      gdt       213: 
1.19      gdt       214: First,
1.27      jnemeth   215: [install NetBSD/amd64](/guide/inst/)
1.19      gdt       216: just as you would if you were not using Xen.
                    217: However, the partitioning approach is very important.
                    218: 
                    219: If you want to use RAIDframe for the dom0, there are no special issues
                    220: for Xen.  Typically one provides RAID storage for the dom0, and the
1.22      gdt       221: domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
1.111     wiz       222: over a RAID1 header to find /boot from a file system within a RAID
1.22      gdt       223: partition; this is no different when booting Xen.
1.19      gdt       224: 
                    225: There are 4 styles of providing backing storage for the virtual disks
1.93      gdt       226: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN.
1.19      gdt       227: 
                    228: With raw partitions, one has a disklabel (or gpt) partition sized for
                    229: each virtual disk to be used by the domU.  (If you are able to predict
                    230: how domU usage will evolve, please add an explanation to the HOWTO.
                    231: Seriously, needs tend to change over time.)
                    232: 
1.27      jnemeth   233: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
                    234: for domU disks.  This is almost as efficient as raw disk partitions
                    235: and more flexible.  Hence raw disk partitions should typically not
                    236: be used.
1.19      gdt       237: 
1.111     wiz       238: One can use files in the dom0 file system, typically created by dd'ing
1.19      gdt       239: /dev/zero to create a specific size.  This is somewhat less efficient,
                    240: but very convenient, as one can cp the files for backup, or move them
                    241: between dom0 hosts.
                    242: 
                    243: Finally, in theory one can place the files backing the domU disks in a
                    244: SAN.  (This is an invitation for someone who has done this to add a
                    245: HOWTO page.)
1.1       mspo      246: 
1.19      gdt       247: Installation of Xen
                    248: -------------------
1.1       mspo      249: 
1.20      gdt       250: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
1.127     gdt       251: pkgsrc (or another matching pair).  See [the pkgsrc
1.140     khorben   252: documentation](https://www.NetBSD.org/docs/pkgsrc/) for help with
1.127     gdt       253: pkgsrc.  Ensure that your packages are recent; the HOWTO does not
                    254: contemplate old builds.
                    255: 
1.20      gdt       256: Next you need to install the selected Xen kernel itself, which is
                    257: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
                    258: For debugging, one may copy xen-debug.gz; this is conceptually similar
                    259: to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
                    260: useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
                    261: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
1.75      gdt       262: of a NetBSD build.  If using i386, use
                    263: releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  (If using Xen
                    264: 3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen.  But you
                    265: should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and
                    266: typically are) left compressed.
                    267: 
1.135     gdt       268: In a dom0, kernfs is mandatory for xend to communicate with the
                    269: kernel, so ensure that /kern is in fstab.  (A standard NetBSD install
                    270: should already mount /kern.)
1.20      gdt       271: 
                    272: Because you already installed NetBSD, you have a working boot setup
                    273: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
1.135     gdt       274: beginning of your root file system, have /boot, and likely also
1.20      gdt       275: /boot.cfg.  (If not, fix before continuing!)
                    276: 
1.152   ! maxv      277: Add a line to /boot.cfg to boot Xen.  See boot.cfg(5) for an
        !           278: example.  The basic line is:
1.20      gdt       279: 
1.152   ! maxv      280: [[!template id=programlisting text="""
        !           281: menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
        !           282: """]]
1.20      gdt       283: 
1.142     gdt       284: which specifies that the dom0 should have 512M, leaving the rest to be
1.77      gdt       285: allocated for domUs.  To use a serial console, use
                    286: 
1.152   ! maxv      287: [[!template id=programlisting text="""
        !           288: menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
        !           289: """]]
1.77      gdt       290: 
                    291: which will use the first serial port for Xen (which counts starting
1.139     gson      292: from 1, unlike NetBSD which counts starting from 0), forcing
                    293: speed/parity.  Because the NetBSD command line lacks a
                    294: "console=pc" argument, it will use the default "xencons" console device,
                    295: which directs the console I/O through Xen to the same console device Xen
                    296: itself uses (in this case, the serial port).
                    297: 
1.152   ! maxv      298: In an attempt to add performance, one can also add:
1.37      gdt       299: 
1.152   ! maxv      300: [[!template id=programlisting text="""
        !           301: dom0_max_vcpus=1 dom0_vcpus_pin
        !           302: """]]
1.37      gdt       303: 
                    304: to force only one vcpu to be provided (since NetBSD dom0 can't use
1.111     wiz       305: more) and to pin that vcpu to a physical CPU.  TODO: benchmark this.
1.20      gdt       306: 
1.93      gdt       307: Xen has [many boot
                    308: options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),
1.111     wiz       309: and other than dom0 memory and max_vcpus, they are generally not
1.93      gdt       310: necessary.
                    311: 
1.20      gdt       312: As with non-Xen systems, you should have a line to boot /netbsd (a
1.127     gdt       313: kernel that works without Xen).  Consider a line to boot /netbsd.ok (a
                    314: fallback version of the non-Xen kernel, updated manually when you are
                    315: sure /netbsd is ok).  Consider also a line to boot fallback versions
                    316: of Xen and the dom0 kernel, but note that non-Xen NetBSD can be used
                    317: to resolve Xen booting issues.
                    318: 
                    319: Probably you want a default=N line to choose Xen in the absence of
                    320: intervention.
1.1       mspo      321: 
1.76      gdt       322: Now, reboot so that you are running a DOM0 kernel under Xen, rather
                    323: than GENERIC without Xen.
                    324: 
1.54      gdt       325: Using grub (historic)
                    326: ---------------------
                    327: 
                    328: Before NetBSD's native bootloader could support Xen, the use of
                    329: grub was recommended.  If necessary, see the
1.135     gdt       330: [old grub information](/ports/xen/howto-grub).
1.54      gdt       331: 
1.28      gdt       332: The [HowTo on Installing into
1.140     khorben   333: RAID-1](https://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
1.28      gdt       334: explains how to set up booting a dom0 with Xen using grub with
                    335: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
1.135     gdt       336: boot.  Now, just create a system with RAID-1, and alter /boot.cfg as
                    337: described above.)
1.28      gdt       338: 
1.21      gdt       339: Configuring Xen
                    340: ---------------
                    341: 
1.53      gdt       342: Xen logs will be in /var/log/xen.
                    343: 
1.76      gdt       344: Now, you have a system that will boot Xen and the dom0 kernel, but not
                    345: do anything else special.  Make sure that you have rebooted into Xen.
                    346: There will be no domUs, and none can be started because you still have
1.102     gdt       347: to configure the dom0 daemons.
1.21      gdt       348: 
1.102     gdt       349: The daemons which should be run vary with Xen version and with whether
1.152   ! maxv      350: one is using xm or xl. Xen 4.2 and up packages use xl. To use xm with 4.2,
        !           351: edit xendomains to use xm instead.
1.31      gdt       352: 
1.132     gdt       353: For 4.1 and up, you should enable xencommons.  Not enabling xencommons
                    354: will result in a hang; it is necessary to hit ^C on the console to let
                    355: the machine finish booting.  If you are using xm (default in 4.1, or
                    356: if you changed xendomains in 4.2), you should also enable xend:
1.31      gdt       357: 
1.152   ! maxv      358: [[!template id=programlisting text="""
        !           359: xend=YES # only if using xm, and only installed <= 4.2
        !           360: xencommons=YES
        !           361: """]]
1.31      gdt       362: 
                    363: TODO: Recommend for/against xen-watchdog.
1.27      jnemeth   364: 
1.53      gdt       365: After you have configured the daemons and either started them (in the
1.79      gdt       366: order given) or rebooted, use xm or xl to inspect Xen's boot messages,
1.102     gdt       367: available resources, and running domains.  An example with xl follows:
1.34      gdt       368: 
1.102     gdt       369:         # xl dmesg
1.43      gdt       370:        [xen's boot info]
1.102     gdt       371:         # xl info
1.43      gdt       372:        [available memory, etc.]
1.102     gdt       373:         # xl list
1.43      gdt       374:         Name              Id  Mem(MB)  CPU  State  Time(s)  Console
                    375:         Domain-0           0       64    0  r----     58.1
1.33      gdt       376: 
1.88      gdt       377: ### Issues with xencommons
                    378: 
                    379: xencommons starts xenstored, which stores data on behalf of dom0 and
                    380: domUs.  It does not currently work to stop and start xenstored.
                    381: Certainly all domUs should be shutdown first, following the sort order
                    382: of the rc.d scripts.  However, the dom0 sets up state with xenstored,
                    383: and is not notified when xenstored exits, leading to not recreating
                    384: the state when the new xenstored starts.  Until there's a mechanism to
                    385: make this work, one should not expect to be able to restart xenstored
                    386: (and thus xencommons).  There is currently no reason to expect that
                    387: this will get fixed any time soon.
                    388: 
1.127     gdt       389: ### No-longer needed advice about devices
                    390: 
                    391: The installation of NetBSD should already have created devices for xen
                    392: (xencons, xenevt, xsd_kva), but if they are not present, create them:
                    393: 
                    394:         cd /dev && sh MAKEDEV xen
                    395: 
1.41      gdt       396: anita (for testing NetBSD)
                    397: --------------------------
                    398: 
1.82      gdt       399: With the setup so far (assuming 4.2/xl), one should be able to run
                    400: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
                    401: root, because anita must create a domU):
                    402: 
                    403:         anita --vmm=xl test file:///usr/obj/i386/
                    404: 
                    405: Alternatively, one can use --vmm=xm to use xm-based domU creation
                    406: instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.
                    407:     
1.40      gdt       408: Xen-specific NetBSD issues
                    409: --------------------------
                    410: 
                    411: There are (at least) two additional things different about NetBSD as a
                    412: dom0 kernel compared to hardware.
                    413: 
1.111     wiz       414: One is that the module ABI is different because some of the #defines
1.109     gdt       415: change, so one must build modules for Xen.  As of netbsd-7, the build
                    416: system does this automatically.  TODO: check this.  (Before building
                    417: Xen modules was added, it was awkward to use modules to the point
                    418: where it was considered that it did not work.)
1.40      gdt       419: 
                    420: The other difference is that XEN3_DOM0 does not have exactly the same
                    421: options as GENERIC.  While it is debatable whether or not this is a
                    422: bug, users should be aware of this and can simply add missing config
                    423: items if desired.
                    424: 
1.15      gdt       425: Updating NetBSD in a dom0
                    426: -------------------------
                    427: 
                    428: This is just like updating NetBSD on bare hardware, assuming the new
                    429: version supports the version of Xen you are running.  Generally, one
                    430: replaces the kernel and reboots, and then overlays userland binaries
                    431: and adjusts /etc.
                    432: 
                    433: Note that one must update both the non-Xen kernel typically used for
                    434: rescue purposes and the DOM0 kernel used with Xen.
                    435: 
1.55      gdt       436: Converting from grub to /boot
                    437: -----------------------------
                    438: 
                    439: These instructions were [TODO: will be] used to convert a system from
                    440: grub to /boot.  The system was originally installed in February of
                    441: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
                    442: over time.  Before these commands, it was running NetBSD 6 i386, Xen
                    443: 4.1 and grub, much like the message linked earlier in the grub
                    444: section.
                    445: 
1.111     wiz       446:         # Install MBR bootblocks on both disks. 
1.55      gdt       447:         fdisk -i /dev/rwd0d
                    448:         fdisk -i /dev/rwd1d
                    449:         # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
                    450:         installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
                    451:         installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
                    452:         # Install secondary boot loader
                    453:         cp -p /usr/mdec/boot /
1.111     wiz       454:         # Create boot.cfg following earlier guidance:
1.142     gdt       455:         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
                    456:         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M
1.55      gdt       457:         menu=GENERIC:boot
                    458:         menu=GENERIC single-user:boot -s
                    459:         menu=GENERIC.ok:boot netbsd.ok
                    460:         menu=GENERIC.ok single-user:boot netbsd.ok -s
                    461:         menu=Drop to boot prompt:prompt
                    462:         default=1
                    463:         timeout=30
                    464: 
                    465: TODO: actually do this and fix it if necessary.
1.22      gdt       466: 
1.102     gdt       467: Upgrading Xen versions
1.15      gdt       468: ---------------------
                    469: 
1.110     gdt       470: Minor version upgrades are trivial.  Just rebuild/replace the
                    471: xenkernel version and copy the new xen.gz to / (where /boot.cfg
                    472: references it), and reboot.
                    473: 
                    474: Major version upgrades are conceptually not difficult, but can run
                    475: into all the issues found when installing Xen.  Assuming migration
                    476: from 4.1 to 4.2, remove the xenkernel41 and xentools41 packages and
                    477: install the xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz
                    478: to /.
1.21      gdt       479: 
1.102     gdt       480: Ensure that the contents of /etc/rc.d/xen* are correct.  Specifically,
                    481: they must match the package you just installed and not be left over
                    482: from some previous installation.
                    483: 
                    484: Enable the correct set of daemons; see the configuring section above.
                    485: (Upgrading from 3.x to 4.x without doing this will result in a hang.)
                    486: 
                    487: Ensure that the domU config files are valid for the new version.
1.110     gdt       488: Specifically, for 4.x remove autorestart=True, and ensure that disks
                    489: are specified with numbers as the second argument, as the examples
                    490: above show, and not NetBSD device names.
1.15      gdt       491: 
1.97      gdt       492: Hardware known to work
                    493: ----------------------
                    494: 
                    495: Arguably, this section is misplaced, and there should be a page of
                    496: hardware that runs NetBSD/amd64 well, with the mostly-well-founded
                    497: assumption that NetBSD/xen runs fine on any modern hardware that
1.129     gdt       498: NetBSD/amd64 runs well on.  Until then, we give motherboard/CPU (and
                    499: sometimes RAM) pairs/triples to aid those choosing a motherboard.
                    500: Note that Xen systems usually do not run X, so a listing here does not
                    501: imply that X works at all.
1.97      gdt       502: 
                    503:         Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC
                    504:         Supermicro ??, Atom C2758 (8 core), 32 GiB ECC
                    505:         ASUS M5A78L-M/USB3 AM3+ microATX, AMD Piledriver X8 4000MHz, 16 GiB ECC
                    506: 
                    507: Older hardware:
                    508: 
1.98      gdt       509:         Intel D915GEV, Pentium4 CPU 3.40GHz, 4GB 533MHz Synchronous DDR2
1.129     gdt       510:         INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU     E6850  @ 3.00GHz"
                    511:         INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU     E8400  @ 3.00GHz"
1.28      gdt       512: 
1.82      gdt       513: Running Xen under qemu
                    514: ----------------------
                    515: 
                    516: The astute reader will note that this section is somewhat twisted.
                    517: However, it can be useful to run Xen under qemu either because the
                    518: version of NetBSD as a dom0 does not run on the hardware in use, or to
                    519: generate automated test cases involving Xen.
                    520: 
1.84      gdt       521: In 2015-01, the following combination was reported to mostly work:
1.82      gdt       522: 
                    523:         host OS: NetBSD/amd64 6.1.4
                    524:         qemu: 2.2.0 from pkgsrc
                    525:         Xen kernel: xenkernel42-4.2.5nb1 from pkgsrc
                    526:         dom0 kernel: NetBSD/amd64 6.1.5
                    527:         Xen tools: xentools42-4.2.5 from pkgsrc
                    528: 
1.140     khorben   529: See [PR 47720](https://gnats.netbsd.org/47720) for a problem with dom0
1.91      gdt       530: shutdown.
1.84      gdt       531: 
1.28      gdt       532: Unprivileged domains (domU)
                    533: ===========================
                    534: 
                    535: This section describes general concepts about domUs.  It does not
1.33      gdt       536: address specific domU operating systems or how to install them.  The
                    537: config files for domUs are typically in /usr/pkg/etc/xen, and are
1.60      wiki      538: typically named so that the file name, domU name and the domU's host
1.33      gdt       539: name match.
                    540: 
1.111     wiz       541: The domU is provided with CPU and memory by Xen, configured by the
1.33      gdt       542: dom0.  The domU is provided with disk and network by the dom0,
                    543: mediated by Xen, and configured in the dom0.
                    544: 
                    545: Entropy in domUs can be an issue; physical disks and network are on
                    546: the dom0.  NetBSD's /dev/random system works, but is often challenged.
                    547: 
1.48      gdt       548: Config files
                    549: ------------
                    550: 
                    551: There is no good order to present config files and the concepts
                    552: surrounding what is being configured.  We first show an example config
                    553: file, and then in the various sections give details.
                    554: 
                    555: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
                    556: for a large number of well-commented examples, mostly for running
                    557: GNU/Linux.
                    558: 
                    559: The following is an example minimal domain configuration file
                    560: "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
                    561: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
                    562: i386 domU).  The domU serves as a network file server.
                    563: 
                    564:         # -*- mode: python; -*-
                    565: 
                    566:         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
                    567:         memory = 1024
                    568:         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
                    569:         disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
                    570:                  'file:/n0/xen/foo-wd1,0x1,w' ]
                    571: 
                    572: The domain will have the same name as the file.  The kernel has the
                    573: host/domU name in it, so that on the dom0 one can update the various
                    574: domUs independently.  The vif line causes an interface to be provided,
                    575: with a specific mac address (do not reuse MAC addresses!), in bridge
                    576: mode.  Two disks are provided, and they are both writable; the bits
                    577: are stored in files and Xen attaches them to a vnd(4) device in the
1.111     wiz       578: dom0 on domain creation.  The system treats xbd0 as the boot device
1.48      gdt       579: without needing explicit configuration.
                    580: 
                    581: By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
                    582: that "xm create" takes the name of a config file, while other commands
                    583: take the name of a domain.  To create the domain, connect to the
                    584: console, create the domain while attaching the console, shutdown the
                    585: domain, and see if it has finished stopping, do (or xl with Xen >=
                    586: 4.2):
                    587: 
                    588:         xm create foo
                    589:         xm console foo
                    590:         xm create -c foo
                    591:         xm shutdown foo
1.90      gdt       592:         xm list
1.48      gdt       593: 
                    594: Typing ^] will exit the console session.  Shutting down a domain is
                    595: equivalent to pushing the power button; a NetBSD domU will receive a
                    596: power-press event and do a clean shutdown.  Shutting down the dom0
                    597: will trigger controlled shutdowns of all configured domUs.
                    598: 
                    599: domU kernels
                    600: ------------
                    601: 
                    602: On a physical computer, the BIOS reads sector 0, and a chain of boot
                    603: loaders finds and loads a kernel.  Normally this comes from the root
1.111     wiz       604: file system.  With Xen domUs, the process is totally different.  The
1.48      gdt       605: normal path is for the domU kernel to be a file in the dom0's
1.111     wiz       606: file system.  At the request of the dom0, Xen loads that kernel into a
1.48      gdt       607: new domU instance and starts execution.  While domU kernels can be
                    608: anyplace, reasonable places to store domU kernels on the dom0 are in /
                    609: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
                    610: config files), or in /u0/xen (where the vdisks are).
                    611: 
1.59      gdt       612: Note that loading the domU kernel from the dom0 implies that boot
                    613: blocks, /boot, /boot.cfg, and so on are all ignored in the domU.
1.48      gdt       614: See the VPS section near the end for discussion of alternate ways to
                    615: obtain domU kernels.
                    616: 
1.33      gdt       617: CPU and memory
                    618: --------------
                    619: 
1.48      gdt       620: A domain is provided with some number of vcpus, less than the number
1.111     wiz       621: of CPUs seen by the hypervisor.  (For a dom0, this is controlled by
1.48      gdt       622: the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
                    623: from the config file by the "vcpus = N" directive.
                    624: 
                    625: A domain is provided with memory; this is controlled in the config
                    626: file by "memory = N" (in megabytes).  In the straightforward case, the
                    627: sum of the the memory allocated to the dom0 and all domUs must be less
1.33      gdt       628: than the available memory.
                    629: 
                    630: Xen also provides a "balloon" driver, which can be used to let domains
                    631: use more memory temporarily.  TODO: Explain better, and explain how
                    632: well it works with NetBSD.
1.28      gdt       633: 
                    634: Virtual disks
                    635: -------------
                    636: 
1.33      gdt       637: With the file/vnd style, typically one creates a directory,
                    638: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
                    639: domUs.  Then, for each domU disk, one writes zeros to a file that then
                    640: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
                    641: for the first virtual disk for the domU called foo.  Writing zeros to
                    642: the file serves two purposes.  One is that preallocating the contents
                    643: improves performance.  The other is that vnd on sparse files has
                    644: failed to work.  TODO: give working/notworking NetBSD versions for
1.127     gdt       645: sparse vnd and gnats reference.  Note that the use of file/vnd for Xen
                    646: is not really different than creating a file-backed virtual disk for
                    647: some other purpose, except that xentools handles the vnconfig
                    648: commands.  To create an empty 4G virtual disk, simply do
1.39      gdt       649: 
                    650:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
1.33      gdt       651: 
1.89      gdt       652: Do not use qemu-img-xen, because this will create sparse file.  There
                    653: have been recent (2015) reports of sparse vnd(4) devices causing
                    654: lockups, but there is apparently no PR.
                    655: 
1.33      gdt       656: With the lvm style, one creates logical devices.  They are then used
1.48      gdt       657: similarly to vnds.  TODO: Add an example with lvm.
                    658: 
                    659: In domU config files, the disks are defined as a sequence of 3-tuples.
                    660: The first element is "method:/path/to/disk".  Common methods are
                    661: "file:" for file-backed vnd. and "phy:" for something that is already
                    662: a (TODO: character or block) device.
                    663: 
                    664: The second element is an artifact of how virtual disks are passed to
                    665: Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
                    666: are given a device name to associate with the disk, and values like
                    667: "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
                    668: as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
                    669: second argument.  The name given is converted to a major/minor by
1.49      gdt       670: calling stat(2) on the name in /dev and this is passed to the domU.
                    671: In the general case, the dom0 and domU can be different operating
1.48      gdt       672: systems, and it is an unwarranted assumption that they have consistent
                    673: numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
                    674: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
1.49      gdt       675: for the second works fine and avoids this issue.  For a GNU/Linux
                    676: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
                    677: /dev/hda1.
1.48      gdt       678: 
                    679: The third element is "w" for writable disks, and "r" for read-only
                    680: disks.
1.28      gdt       681: 
1.127     gdt       682: Note that NetBSD by default creates only vnd[0123].  If you need more
                    683: than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the
                    684: dom0.
                    685: 
                    686: Note that NetBSD by default creates only xbd[0123].  If you need more
                    687: virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU.
                    688: 
1.28      gdt       689: Virtual Networking
                    690: ------------------
                    691: 
1.111     wiz       692: Xen provides virtual Ethernets, each of which connects the dom0 and a
1.46      gdt       693: domU.  For each virtual network, there is an interface "xvifN.M" in
                    694: the dom0, and in domU index N, a matching interface xennetM (NetBSD
                    695: name).  The interfaces behave as if there is an Ethernet with two
1.111     wiz       696: adapters connected.  From this primitive, one can construct various
1.46      gdt       697: configurations.  We focus on two common and useful cases for which
                    698: there are existing scripts: bridging and NAT.
1.28      gdt       699: 
1.48      gdt       700: With bridging (in the example above), the domU perceives itself to be
                    701: on the same network as the dom0.  For server virtualization, this is
                    702: usually best.  Bridging is accomplished by creating a bridge(4) device
                    703: and adding the dom0's physical interface and the various xvifN.0
                    704: interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
                    705: config file.  The bridge must be set up already in the dom0; an
                    706: example /etc/ifconfig.bridge0 is:
1.46      gdt       707: 
                    708:         create
                    709:         up
                    710:         !brconfig bridge0 add wm0
1.28      gdt       711: 
                    712: With NAT, the domU perceives itself to be behind a NAT running on the
                    713: dom0.  This is often appropriate when running Xen on a workstation.
1.48      gdt       714: TODO: NAT appears to be configured by "vif = [ '' ]".
1.28      gdt       715: 
1.49      gdt       716: The MAC address specified is the one used for the interface in the new
1.53      gdt       717: domain.  The interface in dom0 will use this address XOR'd with
1.49      gdt       718: 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
                    719: 
1.33      gdt       720: Sizing domains
                    721: --------------
                    722: 
                    723: Modern x86 hardware has vast amounts of resources.  However, many
                    724: virtual servers can function just fine on far less.  A system with
1.142     gdt       725: 512M of RAM and a 4G disk can be a reasonable choice.  Note that it is
1.33      gdt       726: far easier to adjust virtual resources than physical ones.  For
                    727: memory, it's just a config file edit and a reboot.  For disk, one can
                    728: create a new file and vnconfig it (or lvm), and then dump/restore,
                    729: just like updating physical disks, but without having to be there and
                    730: without those pesky connectors.
                    731: 
1.48      gdt       732: Starting domains automatically
                    733: ------------------------------
1.28      gdt       734: 
1.48      gdt       735: To start domains foo at bar at boot and shut them down cleanly on dom0
                    736: shutdown, in rc.conf add:
1.28      gdt       737: 
1.48      gdt       738:         xendomains="foo bar"
1.28      gdt       739: 
1.111     wiz       740: Note that earlier versions of the xentools41 xendomains rc.d script
                    741: used xl, when one should use xm with 4.1.
1.28      gdt       742: 
                    743: Creating specific unprivileged domains (domU)
                    744: =============================================
1.14      gdt       745: 
                    746: Creating domUs is almost entirely independent of operating system.  We
1.49      gdt       747: have already presented the basics of config files.  Note that you must
                    748: have already completed the dom0 setup so that "xl list" (or "xm list")
                    749: works.
1.14      gdt       750: 
                    751: Creating an unprivileged NetBSD domain (domU)
                    752: ---------------------------------------------
1.1       mspo      753: 
1.49      gdt       754: See the earlier config file, and adjust memory.  Decide on how much
                    755: storage you will provide, and prepare it (file or lvm).
                    756: 
1.111     wiz       757: While the kernel will be obtained from the dom0 file system, the same
1.49      gdt       758: file should be present in the domU as /netbsd so that tools like
                    759: savecore(8) can work.   (This is helpful but not necessary.)
                    760: 
                    761: The kernel must be specifically for Xen and for use as a domU.  The
                    762: i386 and amd64 provide the following kernels:
                    763: 
                    764:         i386 XEN3_DOMU
                    765:         i386 XEN3PAE_DOMU
1.95      gdt       766:         amd64 XEN3_DOMU
1.5       mspo      767: 
1.49      gdt       768: Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
                    769: use the PAE version of the i386 kernel.
                    770: 
                    771: This will boot NetBSD, but this is not that useful if the disk is
                    772: empty.  One approach is to unpack sets onto the disk outside of xen
                    773: (by mounting it, just as you would prepare a physical disk for a
                    774: system you can't run the installer on).
                    775: 
                    776: A second approach is to run an INSTALL kernel, which has a miniroot
                    777: and can load sets from the network.  To do this, copy the INSTALL
                    778: kernel to / and change the kernel line in the config file to:
1.5       mspo      779: 
1.49      gdt       780:         kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
1.5       mspo      781: 
1.49      gdt       782: Then, start the domain as "xl create -c configname".
1.1       mspo      783: 
1.49      gdt       784: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
                    785: line should be used in the config file.
1.1       mspo      786: 
1.3       mspo      787:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
1.1       mspo      788: 
                    789: After booting the domain, the option to install via CDROM may be
1.49      gdt       790: selected.  The CDROM device should be changed to `xbd1d`.
1.1       mspo      791: 
1.49      gdt       792: Once done installing, "halt -p" the new domain (don't reboot or halt,
                    793: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
                    794: config file), switch the config file back to the XEN3_DOMU kernel,
                    795: and start the new domain again. Now it should be able to use "root on
                    796: xbd0a" and you should have a, functional NetBSD domU.
1.1       mspo      797: 
1.49      gdt       798: TODO: check if this is still accurate.
1.1       mspo      799: When the new domain is booting you'll see some warnings about *wscons*
                    800: and the pseudo-terminals. These can be fixed by editing the files
1.5       mspo      801: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
                    802: `/etc/ttys`, except *console*, like this:
1.1       mspo      803: 
1.3       mspo      804:     console "/usr/libexec/getty Pc"         vt100   on secure
                    805:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
                    806:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
                    807:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
                    808:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
1.1       mspo      809: 
1.5       mspo      810: Finally, all screens must be commented out from `/etc/wscons.conf`.
1.1       mspo      811: 
                    812: It is also desirable to add
                    813: 
1.49      gdt       814:         powerd=YES
1.1       mspo      815: 
1.5       mspo      816: in rc.conf. This way, the domain will be properly shut down if
1.53      gdt       817: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
1.1       mspo      818: 
1.92      gdt       819: It is not strictly necessary to have a kernel (as /netbsd) in the domU
1.111     wiz       820: file system.  However, various programs (e.g. netstat) will use that
1.92      gdt       821: kernel to look up symbols to read from kernel virtual memory.  If
                    822: /netbsd is not the running kernel, those lookups will fail.  (This is
                    823: not really a Xen-specific issue, but because the domU kernel is
                    824: obtained from the dom0, it is far more likely to be out of sync or
                    825: missing with Xen.)
                    826: 
1.14      gdt       827: Creating an unprivileged Linux domain (domU)
1.5       mspo      828: --------------------------------------------
1.1       mspo      829: 
                    830: Creating unprivileged Linux domains isn't much different from
                    831: unprivileged NetBSD domains, but there are some details to know.
                    832: 
                    833: First, the second parameter passed to the disk declaration (the '0x1' in
                    834: the example below)
                    835: 
1.3       mspo      836:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
1.1       mspo      837: 
                    838: does matter to Linux. It wants a Linux device number here (e.g. 0x300
1.49      gdt       839: for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
                    840: So, hda1 which has major 3 and minor 1 on a Linux system will have
                    841: device number 0x301.  Alternatively, devices names can be used (hda,
                    842: hdb, ...)  as xentools has a table to map these names to devices
                    843: numbers.  To export a partition to a Linux guest we can use:
1.1       mspo      844: 
1.49      gdt       845:         disk = [ 'phy:/dev/wd0e,0x300,w' ]
                    846:         root = "/dev/hda1 ro"
1.1       mspo      847: 
                    848: and it will appear as /dev/hda on the Linux system, and be used as root
                    849: partition.
                    850: 
1.49      gdt       851: To install the Linux system on the partition to be exported to the
                    852: guest domain, the following method can be used: install
                    853: sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
                    854: that will be the root partition of your Linux domain, and mount it.
                    855: Then copy the files from a working Linux system, make adjustments in
                    856: `/etc` (fstab, network config).  It should also be possible to extract
                    857: binary packages such as .rpm or .deb directly to the mounted partition
                    858: using the appropriate tool, possibly running under NetBSD's Linux
1.111     wiz       859: emulation.  Once the file system has been populated, umount it.  If
                    860: desirable, the file system can be converted to ext3 using tune2fs -j.
1.49      gdt       861: It should now be possible to boot the Linux guest domain, using one of
                    862: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
1.1       mspo      863: 
1.111     wiz       864: To get the Linux console right, you need to add:
1.1       mspo      865: 
1.3       mspo      866:     extra = "xencons=tty1"
1.1       mspo      867: 
1.111     wiz       868: to your configuration since not all Linux distributions auto-attach a
1.1       mspo      869: tty to the xen console.
                    870: 
1.14      gdt       871: Creating an unprivileged Solaris domain (domU)
1.5       mspo      872: ----------------------------------------------
1.1       mspo      873: 
1.50      gdt       874: See possibly outdated
                    875: [Solaris domU instructions](/ports/xen/howto-solaris/).
1.5       mspo      876: 
1.1       mspo      877: 
1.52      gdt       878: PCI passthrough: Using PCI devices in guest domains
                    879: ---------------------------------------------------
1.1       mspo      880: 
1.53      gdt       881: The dom0 can give other domains access to selected PCI
1.52      gdt       882: devices. This can allow, for example, a non-privileged domain to have
                    883: access to a physical network interface or disk controller.  However,
                    884: keep in mind that giving a domain access to a PCI device most likely
                    885: will give the domain read/write access to the whole physical memory,
                    886: as PCs don't have an IOMMU to restrict memory access to DMA-capable
1.53      gdt       887: device.  Also, it's not possible to export ISA devices to non-dom0
1.52      gdt       888: domains, which means that the primary VGA adapter can't be exported.
                    889: A guest domain trying to access the VGA registers will panic.
                    890: 
1.53      gdt       891: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
1.52      gdt       892: not been ported to later versions at this time.
                    893: 
                    894: For a PCI device to be exported to a domU, is has to be attached to
                    895: the "pciback" driver in dom0.  Devices passed to the dom0 via the
                    896: pciback.hide boot parameter will attach to "pciback" instead of the
                    897: usual driver.  The list of devices is specified as "(bus:dev.func)",
1.5       mspo      898: where bus and dev are 2-digit hexadecimal numbers, and func a
                    899: single-digit number:
1.1       mspo      900: 
1.52      gdt       901:         pciback.hide=(00:0a.0)(00:06.0)
1.1       mspo      902: 
1.52      gdt       903: pciback devices should show up in the dom0's boot messages, and the
1.5       mspo      904: devices should be listed in the `/kern/xen/pci` directory.
1.1       mspo      905: 
1.52      gdt       906: PCI devices to be exported to a domU are listed in the "pci" array of
                    907: the domU's config file, with the format "0000:bus:dev.func".
1.1       mspo      908: 
1.52      gdt       909:         pci = [ '0000:00:06.0', '0000:00:0a.0' ]
1.1       mspo      910: 
1.52      gdt       911: In the domU an "xpci" device will show up, to which one or more pci
1.111     wiz       912: buses will attach.  Then the PCI drivers will attach to PCI buses as
1.52      gdt       913: usual.  Note that the default NetBSD DOMU kernels do not have "xpci"
                    914: or any PCI drivers built in by default; you have to build your own
                    915: kernel to use PCI devices in a domU.  Here's a kernel config example;
                    916: note that only the "xpci" lines are unusual.
                    917: 
                    918:         include         "arch/i386/conf/XEN3_DOMU"
                    919: 
1.111     wiz       920:         # Add support for PCI buses to the XEN3_DOMU kernel
1.52      gdt       921:         xpci* at xenbus ?
                    922:         pci* at xpci ?
                    923: 
                    924:         # PCI USB controllers
                    925:         uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
                    926: 
                    927:         # USB bus support
                    928:         usb*    at uhci?
                    929: 
                    930:         # USB Hubs
                    931:         uhub*   at usb?
                    932:         uhub*   at uhub? port ? configuration ? interface ?
                    933: 
                    934:         # USB Mass Storage
                    935:         umass*  at uhub? port ? configuration ? interface ?
                    936:         wd*     at umass?
                    937:         # SCSI controllers
                    938:         ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
                    939: 
                    940:         # SCSI bus support (for both ahc and umass)
                    941:         scsibus* at scsi?
                    942: 
                    943:         # SCSI devices
                    944:         sd*     at scsibus? target ? lun ?      # SCSI disk drives
                    945:         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
1.1       mspo      946: 
                    947: 
1.28      gdt       948: NetBSD as a domU in a VPS
                    949: =========================
                    950: 
                    951: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
                    952: hardware.  This section explains how to deal with Xen in a domU as a
                    953: virtual private server where you do not control or have access to the
1.70      gdt       954: dom0.  This is not intended to be an exhaustive list of VPS providers;
                    955: only a few are mentioned that specifically support NetBSD.
1.28      gdt       956: 
1.52      gdt       957: VPS operators provide varying degrees of access and mechanisms for
                    958: configuration.  The big issue is usually how one controls which kernel
1.111     wiz       959: is booted, because the kernel is nominally in the dom0 file system (to
                    960: which VPS users do not normally have access).  A second issue is how
1.70      gdt       961: to install NetBSD.
1.52      gdt       962: A VPS user may want to compile a kernel for security updates, to run
                    963: npf, run IPsec, or any other reason why someone would want to change
                    964: their kernel.
                    965: 
1.111     wiz       966: One approach is to have an administrative interface to upload a kernel,
1.68      gdt       967: or to select from a prepopulated list.  Other approaches are pygrub
1.59      gdt       968: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
1.111     wiz       969: kernel from the domU file system.  This is closer to a regular physical
1.59      gdt       970: computer, where someone who controls a machine can replace the kernel.
1.52      gdt       971: 
1.74      gdt       972: A second issue is multiple CPUs.  With NetBSD 6, domUs support
                    973: multiple vcpus, and it is typical for VPS providers to enable multiple
                    974: CPUs for NetBSD domUs.
                    975: 
1.68      gdt       976: pygrub
1.59      gdt       977: -------
1.52      gdt       978: 
1.111     wiz       979: pygrub runs in the dom0 and looks into the domU file system.  This
                    980: implies that the domU must have a kernel in a file system in a format
1.68      gdt       981: known to pygrub.  As of 2014, pygrub seems to be of mostly historical
                    982: interest.
1.52      gdt       983: 
1.59      gdt       984: pvgrub
                    985: ------
                    986: 
                    987: pvgrub is a version of grub that uses PV operations instead of BIOS
                    988: calls.  It is booted from the dom0 as the domU kernel, and then reads
1.111     wiz       989: /grub/menu.lst and loads a kernel from the domU file system.
1.59      gdt       990: 
1.70      gdt       991: [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
1.71      gdt       992: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
                    993: (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
1.70      gdt       994: page](http://www.panix.com/v-colo/grub.html), which describes only
1.74      gdt       995: Linux but should be updated to cover NetBSD :-).
1.70      gdt       996: 
                    997: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
                    998: their own kernel.  See then [prgmr.com NetBSD
1.74      gdt       999: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
                   1000: (which is in need of updating).
1.59      gdt      1001: 
1.70      gdt      1002: It appears that [grub's FFS
                   1003: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
                   1004: does not support all aspects of modern FFS, but there are also reports
1.72      gdt      1005: that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT
1.70      gdt      1006: partition for the kernel with the intent that grub can understand it,
                   1007: which leads to /netbsd not being the actual kernel.  One must remember
1.111     wiz      1008: to update the special boot partition.
1.59      gdt      1009: 
                   1010: Amazon
                   1011: ------
                   1012: 
1.143     wiki     1013: See the [Amazon EC2 page](/amazon_ec2/).
1.44      gdt      1014: 
1.65      gdt      1015: TODO items for improving NetBSD/xen
                   1016: ===================================
                   1017: 
1.93      gdt      1018: * Make the NetBSD dom0 kernel work with SMP.
                   1019: * Test the Xen 4.5 packages adequately to be able to recommend them as
                   1020:   the standard approach.
                   1021: * Get PCI passthrough working on Xen 4.5
1.65      gdt      1022: * Get pvgrub into pkgsrc, either via xentools or separately.
                   1023: * grub
1.70      gdt      1024:   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary
1.66      gdt      1025:     fragsize/blocksize (UFS2 support may be present; the point is to
1.111     wiz      1026:     make it so that with any UFS1/UFS2 file system setup that works
1.66      gdt      1027:     with NetBSD grub will also work).
1.140     khorben  1028:     See [pkg/40258](https://gnats.netbsd.org/40258).
1.65      gdt      1029:   * Push patches upstream.
                   1030:   * Get UFS2 patches into pvgrub.
                   1031: * Add support for PV ops to a version of /boot, and make it usable as
                   1032:   a kernel in Xen, similar to pvgrub.
1.93      gdt      1033: 
                   1034: Random pointers
                   1035: ===============
                   1036: 
1.117     gdt      1037: This section contains links from elsewhere not yet integrated into the
                   1038: HOWTO, and other guides.
1.93      gdt      1039: 
                   1040: * http://www.lumbercartel.ca/library/xen/
                   1041: * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html
1.117     gdt      1042: * https://gmplib.org/~tege/xen.html

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