Annotation of wikisrc/ports/xen/howto.mdwn, revision 1.99

1.5       mspo        1: Introduction
1.13      gdt         2: ============
1.1       mspo        3: 
                      4: [![[Xen
1.57      gdt         5: screenshot]](http://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](http://www.netbsd.org/gallery/in-Action/hubertf-xen.png)
1.1       mspo        6: 
1.58      gdt         7: Xen is a hypervisor (or virtual machine monitor) for x86 hardware
1.12      gdt         8: (i686-class or higher), which supports running multiple guest
1.58      gdt         9: operating systems on a single physical machine.  Xen is a Type 1 or
                     10: bare-metal hypervisor; one uses the Xen kernel to control the CPU,
                     11: memory and console, a dom0 operating system which mediates access to
                     12: other hardware (e.g., disks, network, USB), and one or more domU
                     13: operating systems which operate in an unprivileged virtualized
                     14: environment.  IO requests from the domU systems are forwarded by the
                     15: hypervisor (Xen) to the dom0 to be fulfilled.
1.12      gdt        16: 
                     17: Xen supports two styles of guests.  The original is Para-Virtualized
                     18: (PV) which means that the guest OS does not attempt to access hardware
                     19: directly, but instead makes hypercalls to the hypervisor.  This is
                     20: analogous to a user-space program making system calls.  (The dom0
                     21: operating system uses PV calls for some functions, such as updating
                     22: memory mapping page tables, but has direct hardware access for disk
                     23: and network.)   PV guests must be specifically coded for Xen.
                     24: 
                     25: The more recent style is HVM, which means that the guest does not have
                     26: code for Xen and need not be aware that it is running under Xen.
                     27: Attempts to access hardware registers are trapped and emulated.  This
                     28: style is less efficient but can run unmodified guests.
                     29: 
1.29      gdt        30: Generally any amd64 machine will work with Xen and PV guests.  In
                     31: theory i386 computers without amd64 support can be used for Xen <=
                     32: 4.2, but we have no recent reports of this working (this is a hint).
                     33: For HVM guests, the VT or VMX cpu feature (Intel) or SVM/HVM/VT
                     34: (amd64) is needed; "cpuctl identify 0" will show this.  TODO: Clean up
                     35: and check the above features.
1.19      gdt        36: 
1.27      jnemeth    37: At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
1.12      gdt        38: The dom0 can start one or more domUs.  (Booting is explained in detail
                     39: in the dom0 section.)
                     40: 
                     41: NetBSD supports Xen in that it can serve as dom0, be used as a domU,
                     42: and that Xen kernels and tools are available in pkgsrc.  This HOWTO
                     43: attempts to address both the case of running a NetBSD dom0 on hardware
1.24      gdt        44: and running domUs under it (NetBSD and other), and also running NetBSD
                     45: as a domU in a VPS.
1.12      gdt        46: 
1.20      gdt        47: Some versions of Xen support "PCI passthrough", which means that
                     48: specific PCI devices can be made available to a specific domU instead
                     49: of the dom0.  This can be useful to let a domU run X11, or access some
                     50: network interface or other peripheral.
                     51: 
1.54      gdt        52: NetBSD used to support Xen2; this has been removed.
                     53: 
1.12      gdt        54: Prerequisites
1.13      gdt        55: -------------
1.12      gdt        56: 
                     57: Installing NetBSD/Xen is not extremely difficult, but it is more
                     58: complex than a normal installation of NetBSD.
1.15      gdt        59: In general, this HOWTO is occasionally overly restrictive about how
                     60: things must be done, guiding the reader to stay on the established
                     61: path when there are no known good reasons to stray.
1.12      gdt        62: 
                     63: This HOWTO presumes a basic familiarity with the Xen system
1.16      gdt        64: architecture.  This HOWTO presumes familiarity with installing NetBSD
                     65: on i386/amd64 hardware and installing software from pkgsrc.
1.27      jnemeth    66: See also the [Xen website](http://www.xenproject.org/).
1.1       mspo       67: 
1.15      gdt        68: Versions of Xen and NetBSD
                     69: ==========================
                     70: 
1.27      jnemeth    71: Most of the installation concepts and instructions are independent
                     72: of Xen version and NetBSD version.  This section gives advice on
                     73: which version to choose.  Versions not in pkgsrc and older unsupported
                     74: versions of NetBSD are intentionally ignored.
1.15      gdt        75: 
                     76: Xen
                     77: ---
                     78: 
                     79: In NetBSD, xen is provided in pkgsrc, via matching pairs of packages
                     80: xenkernel and xentools.  We will refer only to the kernel versions,
                     81: but note that both packages must be installed together and must have
                     82: matching versions.
                     83: 
                     84: xenkernel3 and xenkernel33 provide Xen 3.1 and 3.3.  These no longer
1.20      gdt        85: receive security patches and should not be used.  Xen 3.1 supports PCI
1.29      gdt        86: passthrough.  Xen 3.1 supports non-PAE on i386.
1.15      gdt        87: 
                     88: xenkernel41 provides Xen 4.1.  This is no longer maintained by Xen,
                     89: but as of 2014-12 receives backported security patches.  It is a
                     90: reasonable although trailing-edge choice.
                     91: 
                     92: xenkernel42 provides Xen 4.2.  This is maintained by Xen, but old as
                     93: of 2014-12.
                     94: 
1.85      gdt        95: xenkernel45 provides Xen 4.5.  This is new to pkgsrc as of 2015-01 and
                     96: not yet recommended for other than experimental/testing use.
                     97: 
1.96      gdt        98: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
                     99: 
1.15      gdt       100: Ideally newer versions of Xen will be added to pkgsrc.
                    101: 
1.85      gdt       102: Note that NetBSD support is called XEN3.  It works with Xen 3 and Xen
                    103: 4 because the hypercall interface has been stable.
1.20      gdt       104: 
1.19      gdt       105: Xen command program
                    106: -------------------
                    107: 
1.79      gdt       108: Early Xen used a program called xm to manipulate the system from the
1.19      gdt       109: dom0.  Starting in 4.1, a replacement program with similar behavior
1.79      gdt       110: called xl is provided, but it does not work well in 4.1.  In 4.2, both
                    111: xm and xl work fine.  4.4 is the last version that has xm.  You must
                    112: choose one or the other, because it affects which daemons you run.
1.19      gdt       113: 
1.15      gdt       114: NetBSD
                    115: ------
                    116: 
                    117: The netbsd-5, netbsd-6, netbsd-7, and -current branches are all
                    118: reasonable choices, with more or less the same considerations for
                    119: non-Xen use.  Therefore, netbsd-6 is recommended as the stable version
1.29      gdt       120: of the most recent release for production use.  For those wanting to
                    121: learn Xen or without production stability concerns, netbsd-7 is likely
                    122: most appropriate.
1.15      gdt       123: 
                    124: As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
                    125: no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
                    126: need SMP; the lack of support is really a problem when using a dom0 as
                    127: a normal computer.)
                    128: 
1.18      gdt       129: Architecture
                    130: ------------
                    131: 
1.29      gdt       132: Xen itself can run on i386 or amd64 machines.  (Practically, almost
1.99    ! gdt       133: any computer where one would want to run Xen today supports amd64.)
        !           134: 
        !           135: Xen, the dom0 kernel, and each domU kernel can be either i386 or
        !           136: amd64.  When building a xenkernel package, one obtains i386 on an i386
        !           137: host, and amd64 on an amd64 host.  If the xen kernel is i386, then the
        !           138: dom0 kernel and all domU kernels must be i386.  With an amd64 xen
        !           139: kernel, an amd64 dom0 kernel is known to work, and an i386 dom0 kernel
        !           140: should in theory work.  An amd64 xen/dom0 is known to support both
        !           141: i386 and amd64 domUs.
        !           142: 
        !           143: Except for an odd case with Xen 3.1, i386 dom0 and domU kernels must
        !           144: be PAE; these are built by default.  (Note that emacs (at least) fails
        !           145: if run on i386 with PAE when built without, and vice versa, presumably
        !           146: due to bugs in the undump code.)
        !           147: 
        !           148: Because of the above, the standard approach is to use amd64 for the
        !           149: dom0.
1.29      gdt       150: 
                    151: Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify
                    152: if this is about the CPU having to be amd64, or about the dom0 kernel
                    153: having to be amd64.
                    154: 
1.89      gdt       155: Stability
                    156: ---------
                    157: 
                    158: Mostly, NetBSD as a dom0 or domU is quite stable.
                    159: However, there are some open PRs indicating problems.
                    160: 
1.91      gdt       161:  - [PR 48125](http://gnats.netbsd.org/48125)
                    162:  - [PR 47720](http://gnats.netbsd.org/47720)
1.89      gdt       163: 
                    164: Note also that there are issues with sparse vnd(4) instances, but
                    165: these are not about Xen.
                    166: 
1.15      gdt       167: Recommendation
                    168: --------------
                    169: 
1.18      gdt       170: Therefore, this HOWTO recommends running xenkernel42 (and xentools42),
1.30      gdt       171: xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the
                    172: dom0.  Either the i386 or amd64 of NetBSD may be used as domUs.
1.15      gdt       173: 
1.36      gdt       174: Build problems
                    175: --------------
                    176: 
                    177: Ideally, all versions of Xen in pkgsrc would build on all versions of
                    178: NetBSD on both i386 and amd64.  However, that isn't the case.  Besides
                    179: aging code and aging compilers, qemu (included in xentools for HVM
1.62      gdt       180: support) is difficult to build.  The following are known to work or FAIL:
1.36      gdt       181: 
1.62      gdt       182:         xenkernel3 netbsd-5 amd64
1.63      gdt       183:         xentools3 netbsd-5 amd64
1.64      gdt       184:         xentools3=hvm netbsd-5 amd64 ????
1.62      gdt       185:         xenkernel33 netbsd-5 amd64
1.63      gdt       186:         xentools33 netbsd-5 amd64
1.36      gdt       187:         xenkernel41 netbsd-5 amd64
                    188:         xentools41 netbsd-5 amd64
1.62      gdt       189:         xenkernel42 netbsd-5 amd64
1.64      gdt       190:         xentools42 netbsd-5 amd64
1.62      gdt       191: 
                    192:         xenkernel3 netbsd-6 i386 FAIL
                    193:         xentools3 netbsd-6 i386
1.63      gdt       194:         xentools3-hvm netbsd-6 i386 FAIL (dependencies fail)
                    195:         xenkernel33 netbsd-6 i386
                    196:         xentools33 netbsd-6 i386
1.36      gdt       197:         xenkernel41 netbsd-6 i386
                    198:         xentools41 netbsd-6 i386
1.63      gdt       199:         xenkernel42 netbsd-6 i386
1.64      gdt       200:         xentools42 netbsd-6 i386 *MIXED
                    201: 
1.69      gdt       202:        (all 3 and 33 seem to FAIL)
                    203:         xenkernel41 netbsd-7 i386
                    204:         xentools41 netbsd-7 i386
                    205:         xenkernel42 netbsd-7 i386
                    206:         xentools42 netbsd-7 i386 ??FAIL
                    207: 
1.64      gdt       208: (*On netbsd-6 i386, there is a xentools42 in the 2014Q3 official builds,
                    209: but it does not build for gdt.)
1.36      gdt       210: 
1.15      gdt       211: NetBSD as a dom0
                    212: ================
                    213: 
                    214: NetBSD can be used as a dom0 and works very well.  The following
                    215: sections address installation, updating NetBSD, and updating Xen.
1.19      gdt       216: Note that it doesn't make sense to talk about installing a dom0 OS
                    217: without also installing Xen itself.  We first address installing
                    218: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
                    219: NetBSD install to a dom0 install by just changing the kernel and boot
                    220: configuration.
1.15      gdt       221: 
1.45      gdt       222: For experimenting with Xen, a machine with as little as 1G of RAM and
                    223: 100G of disk can work.  For running many domUs in productions, far
                    224: more will be needed.
                    225: 
1.15      gdt       226: Styles of dom0 operation
                    227: ------------------------
                    228: 
                    229: There are two basic ways to use Xen.  The traditional method is for
                    230: the dom0 to do absolutely nothing other than providing support to some
                    231: number of domUs.  Such a system was probably installed for the sole
                    232: purpose of hosting domUs, and sits in a server room on a UPS.
                    233: 
                    234: The other way is to put Xen under a normal-usage computer, so that the
                    235: dom0 is what the computer would have been without Xen, perhaps a
                    236: desktop or laptop.  Then, one can run domUs at will.  Purists will
                    237: deride this as less secure than the previous approach, and for a
                    238: computer whose purpose is to run domUs, they are right.  But Xen and a
1.93      gdt       239: dom0 (without domUs) is not meaningfully less secure than the same
1.15      gdt       240: things running without Xen.  One can boot Xen or boot regular NetBSD
                    241: alternately with little problems, simply refraining from starting the
                    242: Xen daemons when not running Xen.
                    243: 
                    244: Note that NetBSD as dom0 does not support multiple CPUs.  This will
1.51      gdt       245: limit the performance of the Xen/dom0 workstation approach.  In theory
                    246: the only issue is that the "backend drivers" are not yet MPSAFE:
                    247:   http://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html
1.15      gdt       248: 
1.19      gdt       249: Installation of NetBSD
                    250: ----------------------
1.13      gdt       251: 
1.19      gdt       252: First,
1.27      jnemeth   253: [install NetBSD/amd64](/guide/inst/)
1.19      gdt       254: just as you would if you were not using Xen.
                    255: However, the partitioning approach is very important.
                    256: 
                    257: If you want to use RAIDframe for the dom0, there are no special issues
                    258: for Xen.  Typically one provides RAID storage for the dom0, and the
1.22      gdt       259: domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
                    260: over a RAID1 header to find /boot from a filesystem within a RAID
                    261: partition; this is no different when booting Xen.
1.19      gdt       262: 
                    263: There are 4 styles of providing backing storage for the virtual disks
1.93      gdt       264: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN.
1.19      gdt       265: 
                    266: With raw partitions, one has a disklabel (or gpt) partition sized for
                    267: each virtual disk to be used by the domU.  (If you are able to predict
                    268: how domU usage will evolve, please add an explanation to the HOWTO.
                    269: Seriously, needs tend to change over time.)
                    270: 
1.27      jnemeth   271: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
                    272: for domU disks.  This is almost as efficient as raw disk partitions
                    273: and more flexible.  Hence raw disk partitions should typically not
                    274: be used.
1.19      gdt       275: 
                    276: One can use files in the dom0 filesystem, typically created by dd'ing
                    277: /dev/zero to create a specific size.  This is somewhat less efficient,
                    278: but very convenient, as one can cp the files for backup, or move them
                    279: between dom0 hosts.
                    280: 
                    281: Finally, in theory one can place the files backing the domU disks in a
                    282: SAN.  (This is an invitation for someone who has done this to add a
                    283: HOWTO page.)
1.1       mspo      284: 
1.19      gdt       285: Installation of Xen
                    286: -------------------
1.1       mspo      287: 
1.20      gdt       288: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
                    289: pkgsrc (or another matching pair).
                    290: See [the pkgsrc
                    291: documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc.
                    292: 
                    293: For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More
                    294: recent versions have HVM support integrated in the main xentools
                    295: package.  It is entirely reasonable to run only PV guests.
                    296: 
                    297: Next you need to install the selected Xen kernel itself, which is
                    298: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
                    299: For debugging, one may copy xen-debug.gz; this is conceptually similar
                    300: to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
                    301: useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
                    302: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
1.75      gdt       303: of a NetBSD build.  If using i386, use
                    304: releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  (If using Xen
                    305: 3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen.  But you
                    306: should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and
                    307: typically are) left compressed.
                    308: 
                    309: In a dom0 kernel, kernfs is mandatory for xend to comunicate with the
                    310: kernel, so ensure that /kern is in fstab.  TODO: Say this is default,
                    311: or file a PR and give a reference.
1.20      gdt       312: 
                    313: Because you already installed NetBSD, you have a working boot setup
                    314: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
                    315: beginning of your root filesystem, /boot present, and likely
                    316: /boot.cfg.  (If not, fix before continuing!)
                    317: 
1.76      gdt       318: Add a line to to /boot.cfg to boot Xen.  See boot.cfg(5) for an
                    319: example.  The basic line is
1.20      gdt       320: 
1.37      gdt       321:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
1.20      gdt       322: 
                    323: which specifies that the dom0 should have 256M, leaving the rest to be
1.77      gdt       324: allocated for domUs.  To use a serial console, use
                    325: 
                    326:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=com0;multiboot /xen.gz dom0_mem=256M console=com1 com1=9600,8n1
                    327: 
                    328: which will use the first serial port for Xen (which counts starting
                    329: from 1), forcing speed/parity, and also for NetBSD (which counts
                    330: starting at 0).  In an attempt to add performance, one can also add
1.37      gdt       331: 
                    332:         dom0_max_vcpus=1 dom0_vcpus_pin
                    333: 
                    334: to force only one vcpu to be provided (since NetBSD dom0 can't use
                    335: more) and to pin that vcpu to a physical cpu.  TODO: benchmark this.
1.20      gdt       336: 
1.93      gdt       337: Xen has [many boot
                    338: options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),
                    339: and other tham dom0 memory and max_vcpus, they are generally not
                    340: necessary.
                    341: 
1.20      gdt       342: As with non-Xen systems, you should have a line to boot /netbsd (a
                    343: kernel that works without Xen) and fallback versions of the non-Xen
                    344: kernel, Xen, and the dom0 kernel.
1.1       mspo      345: 
1.76      gdt       346: Now, reboot so that you are running a DOM0 kernel under Xen, rather
                    347: than GENERIC without Xen.
                    348: 
1.54      gdt       349: Using grub (historic)
                    350: ---------------------
                    351: 
                    352: Before NetBSD's native bootloader could support Xen, the use of
                    353: grub was recommended.  If necessary, see the
                    354: [old grub information](/ports/xen/howto-grub/).
                    355: 
1.28      gdt       356: The [HowTo on Installing into
                    357: RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
                    358: explains how to set up booting a dom0 with Xen using grub with
                    359: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
                    360: boot.)
                    361: 
1.21      gdt       362: Configuring Xen
                    363: ---------------
                    364: 
1.53      gdt       365: Xen logs will be in /var/log/xen.
                    366: 
1.76      gdt       367: Now, you have a system that will boot Xen and the dom0 kernel, but not
                    368: do anything else special.  Make sure that you have rebooted into Xen.
                    369: There will be no domUs, and none can be started because you still have
                    370: to configure the dom0 tools.  The daemons which should be run vary
                    371: with Xen version and with whether one is using xm or xl.  Note that
                    372: xend is for supporting "xm", and should only be used if you plan on
                    373: using "xm".  Do NOT enable xend if you plan on using "xl" as it will
1.87      gdt       374: cause problems.  Running xl without xencommons=YES (and starting it)
                    375: will result in a hang (so don't do that; follow the HOWTO!).
1.21      gdt       376: 
1.43      gdt       377: The installation of NetBSD should already have created devices for xen
                    378: (xencons, xenevt), but if they are not present, create them:
                    379: 
                    380:         cd /dev && sh MAKEDEV xen
                    381: 
1.31      gdt       382: TODO: Give 3.1 advice (or remove it from pkgsrc).
                    383: 
                    384: For 3.3 (and thus xm), add to rc.conf (but note that you should have
                    385: installed 4.1 or 4.2):
                    386: 
1.32      gdt       387:         xend=YES
                    388:         xenbackendd=YES
1.31      gdt       389: 
1.33      gdt       390: For 4.1 (and thus xm; xl is believed not to work well), add to rc.conf:
1.31      gdt       391: 
1.53      gdt       392:         xencommons=YES
1.31      gdt       393:         xend=YES
                    394: 
1.56      gdt       395: (If you are using xentools41 from before 2014-12-26, change
                    396: rc.d/xendomains to use xm rather than xl.)
1.31      gdt       397: 
1.33      gdt       398: For 4.2 with xm, add to rc.conf
                    399: 
1.53      gdt       400:         xencommons=YES
1.33      gdt       401:         xend=YES
                    402: 
1.79      gdt       403: For 4.2 with xl, add to rc.conf:
1.31      gdt       404: 
1.53      gdt       405:         xencommons=YES
1.31      gdt       406:         TODO: explain if there is a xend replacement
                    407: 
1.86      gdt       408: For 4.5 (and thus with xl), add to rc.conf:
                    409: 
                    410:         xencommons=YES
                    411:         TODO: explain if there is a xend replacement
                    412: 
1.31      gdt       413: TODO: Recommend for/against xen-watchdog.
1.27      jnemeth   414: 
1.53      gdt       415: After you have configured the daemons and either started them (in the
1.79      gdt       416: order given) or rebooted, use xm or xl to inspect Xen's boot messages,
                    417: available resources, and running domains.  An example with xm follows:
1.34      gdt       418: 
1.43      gdt       419:         # xm dmesg
                    420:        [xen's boot info]
                    421:         # xm info
                    422:        [available memory, etc.]
                    423:         # xm list
                    424:         Name              Id  Mem(MB)  CPU  State  Time(s)  Console
                    425:         Domain-0           0       64    0  r----     58.1
1.33      gdt       426: 
1.79      gdt       427: With xl, the commands are the same, and the output may be slightly
1.83      gdt       428: different.  TODO: add example output for xl before the xm example,
                    429: after confirming on 4.2 and resolving the TODO about rc.conf.
1.79      gdt       430: 
1.88      gdt       431: ### Issues with xencommons
                    432: 
                    433: xencommons starts xenstored, which stores data on behalf of dom0 and
                    434: domUs.  It does not currently work to stop and start xenstored.
                    435: Certainly all domUs should be shutdown first, following the sort order
                    436: of the rc.d scripts.  However, the dom0 sets up state with xenstored,
                    437: and is not notified when xenstored exits, leading to not recreating
                    438: the state when the new xenstored starts.  Until there's a mechanism to
                    439: make this work, one should not expect to be able to restart xenstored
                    440: (and thus xencommons).  There is currently no reason to expect that
                    441: this will get fixed any time soon.
                    442: 
1.41      gdt       443: anita (for testing NetBSD)
                    444: --------------------------
                    445: 
1.82      gdt       446: With the setup so far (assuming 4.2/xl), one should be able to run
                    447: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
                    448: root, because anita must create a domU):
                    449: 
                    450:         anita --vmm=xl test file:///usr/obj/i386/
                    451: 
                    452: Alternatively, one can use --vmm=xm to use xm-based domU creation
                    453: instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.
                    454:     
1.40      gdt       455: Xen-specific NetBSD issues
                    456: --------------------------
                    457: 
                    458: There are (at least) two additional things different about NetBSD as a
                    459: dom0 kernel compared to hardware.
                    460: 
                    461: One is that modules are not usable in DOM0 kernels, so one must
                    462: compile in what's needed.  It's not really that modules cannot work,
                    463: but that modules must be built for XEN3_DOM0 because some of the
                    464: defines change and the normal module builds don't do this.  Basically,
                    465: enabling Xen changes the kernel ABI, and the module build system
                    466: doesn't cope with this.
                    467: 
                    468: The other difference is that XEN3_DOM0 does not have exactly the same
                    469: options as GENERIC.  While it is debatable whether or not this is a
                    470: bug, users should be aware of this and can simply add missing config
                    471: items if desired.
                    472: 
1.15      gdt       473: Updating NetBSD in a dom0
                    474: -------------------------
                    475: 
                    476: This is just like updating NetBSD on bare hardware, assuming the new
                    477: version supports the version of Xen you are running.  Generally, one
                    478: replaces the kernel and reboots, and then overlays userland binaries
                    479: and adjusts /etc.
                    480: 
                    481: Note that one must update both the non-Xen kernel typically used for
                    482: rescue purposes and the DOM0 kernel used with Xen.
                    483: 
1.55      gdt       484: Converting from grub to /boot
                    485: -----------------------------
                    486: 
                    487: These instructions were [TODO: will be] used to convert a system from
                    488: grub to /boot.  The system was originally installed in February of
                    489: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
                    490: over time.  Before these commands, it was running NetBSD 6 i386, Xen
                    491: 4.1 and grub, much like the message linked earlier in the grub
                    492: section.
                    493: 
                    494:         # Install mbr bootblocks on both disks. 
                    495:         fdisk -i /dev/rwd0d
                    496:         fdisk -i /dev/rwd1d
                    497:         # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
                    498:         installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
                    499:         installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
                    500:         # Install secondary boot loader
                    501:         cp -p /usr/mdec/boot /
                    502:         # Create boog.cfg following earlier guidance:
                    503:         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
                    504:         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M
                    505:         menu=GENERIC:boot
                    506:         menu=GENERIC single-user:boot -s
                    507:         menu=GENERIC.ok:boot netbsd.ok
                    508:         menu=GENERIC.ok single-user:boot netbsd.ok -s
                    509:         menu=Drop to boot prompt:prompt
                    510:         default=1
                    511:         timeout=30
                    512: 
                    513: TODO: actually do this and fix it if necessary.
1.22      gdt       514: 
1.15      gdt       515: Updating Xen versions
                    516: ---------------------
                    517: 
1.21      gdt       518: Updating Xen is conceptually not difficult, but can run into all the
                    519: issues found when installing Xen.  Assuming migration from 4.1 to 4.2,
                    520: remove the xenkernel41 and xentools41 packages and install the
                    521: xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.
                    522: 
                    523: Ensure that the contents of /etc/rc.d/xen* are correct.  Enable the
                    524: correct set of daemons.  Ensure that the domU config files are valid
                    525: for the new version.
1.15      gdt       526: 
1.97      gdt       527: Hardware known to work
                    528: ----------------------
                    529: 
                    530: Arguably, this section is misplaced, and there should be a page of
                    531: hardware that runs NetBSD/amd64 well, with the mostly-well-founded
                    532: assumption that NetBSD/xen runs fine on any modern hardware that
                    533: NetBSD/amd64 runs well on.  Until then, we give motherboard/CPU/RAM
                    534: triples to aid those choosing a motherboard.  Note that Xen systems
                    535: usually do not run X, so a listing here does not imply that X works at
                    536: all.
                    537: 
                    538:         Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC
                    539:         Supermicro ??, Atom C2758 (8 core), 32 GiB ECC
                    540:         ASUS M5A78L-M/USB3 AM3+ microATX, AMD Piledriver X8 4000MHz, 16 GiB ECC
                    541: 
                    542: Older hardware:
                    543: 
1.98      gdt       544:         Intel D915GEV, Pentium4 CPU 3.40GHz, 4GB 533MHz Synchronous DDR2
1.28      gdt       545: 
1.82      gdt       546: Running Xen under qemu
                    547: ----------------------
                    548: 
                    549: The astute reader will note that this section is somewhat twisted.
                    550: However, it can be useful to run Xen under qemu either because the
                    551: version of NetBSD as a dom0 does not run on the hardware in use, or to
                    552: generate automated test cases involving Xen.
                    553: 
1.84      gdt       554: In 2015-01, the following combination was reported to mostly work:
1.82      gdt       555: 
                    556:         host OS: NetBSD/amd64 6.1.4
                    557:         qemu: 2.2.0 from pkgsrc
                    558:         Xen kernel: xenkernel42-4.2.5nb1 from pkgsrc
                    559:         dom0 kernel: NetBSD/amd64 6.1.5
                    560:         Xen tools: xentools42-4.2.5 from pkgsrc
                    561: 
1.91      gdt       562: See [PR 47720](http://gnats.netbsd.org/47720) for a problem with dom0
                    563: shutdown.
1.84      gdt       564: 
1.28      gdt       565: Unprivileged domains (domU)
                    566: ===========================
                    567: 
                    568: This section describes general concepts about domUs.  It does not
1.33      gdt       569: address specific domU operating systems or how to install them.  The
                    570: config files for domUs are typically in /usr/pkg/etc/xen, and are
1.60      wiki      571: typically named so that the file name, domU name and the domU's host
1.33      gdt       572: name match.
                    573: 
                    574: The domU is provided with cpu and memory by Xen, configured by the
                    575: dom0.  The domU is provided with disk and network by the dom0,
                    576: mediated by Xen, and configured in the dom0.
                    577: 
                    578: Entropy in domUs can be an issue; physical disks and network are on
                    579: the dom0.  NetBSD's /dev/random system works, but is often challenged.
                    580: 
1.48      gdt       581: Config files
                    582: ------------
                    583: 
                    584: There is no good order to present config files and the concepts
                    585: surrounding what is being configured.  We first show an example config
                    586: file, and then in the various sections give details.
                    587: 
                    588: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
                    589: for a large number of well-commented examples, mostly for running
                    590: GNU/Linux.
                    591: 
                    592: The following is an example minimal domain configuration file
                    593: "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
                    594: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
                    595: i386 domU).  The domU serves as a network file server.
                    596: 
                    597:         # -*- mode: python; -*-
                    598: 
                    599:         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
                    600:         memory = 1024
                    601:         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
                    602:         disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
                    603:                  'file:/n0/xen/foo-wd1,0x1,w' ]
                    604: 
                    605: The domain will have the same name as the file.  The kernel has the
                    606: host/domU name in it, so that on the dom0 one can update the various
                    607: domUs independently.  The vif line causes an interface to be provided,
                    608: with a specific mac address (do not reuse MAC addresses!), in bridge
                    609: mode.  Two disks are provided, and they are both writable; the bits
                    610: are stored in files and Xen attaches them to a vnd(4) device in the
                    611: dom0 on domain creation.  The system treates xbd0 as the boot device
                    612: without needing explicit configuration.
                    613: 
                    614: By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
                    615: that "xm create" takes the name of a config file, while other commands
                    616: take the name of a domain.  To create the domain, connect to the
                    617: console, create the domain while attaching the console, shutdown the
                    618: domain, and see if it has finished stopping, do (or xl with Xen >=
                    619: 4.2):
                    620: 
                    621:         xm create foo
                    622:         xm console foo
                    623:         xm create -c foo
                    624:         xm shutdown foo
1.90      gdt       625:         xm list
1.48      gdt       626: 
                    627: Typing ^] will exit the console session.  Shutting down a domain is
                    628: equivalent to pushing the power button; a NetBSD domU will receive a
                    629: power-press event and do a clean shutdown.  Shutting down the dom0
                    630: will trigger controlled shutdowns of all configured domUs.
                    631: 
                    632: domU kernels
                    633: ------------
                    634: 
                    635: On a physical computer, the BIOS reads sector 0, and a chain of boot
                    636: loaders finds and loads a kernel.  Normally this comes from the root
                    637: filesystem.  With Xen domUs, the process is totally different.  The
                    638: normal path is for the domU kernel to be a file in the dom0's
                    639: filesystem.  At the request of the dom0, Xen loads that kernel into a
                    640: new domU instance and starts execution.  While domU kernels can be
                    641: anyplace, reasonable places to store domU kernels on the dom0 are in /
                    642: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
                    643: config files), or in /u0/xen (where the vdisks are).
                    644: 
1.59      gdt       645: Note that loading the domU kernel from the dom0 implies that boot
                    646: blocks, /boot, /boot.cfg, and so on are all ignored in the domU.
1.48      gdt       647: See the VPS section near the end for discussion of alternate ways to
                    648: obtain domU kernels.
                    649: 
1.33      gdt       650: CPU and memory
                    651: --------------
                    652: 
1.48      gdt       653: A domain is provided with some number of vcpus, less than the number
                    654: of cpus seen by the hypervisor.  (For a dom0, this is controlled by
                    655: the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
                    656: from the config file by the "vcpus = N" directive.
                    657: 
                    658: A domain is provided with memory; this is controlled in the config
                    659: file by "memory = N" (in megabytes).  In the straightforward case, the
                    660: sum of the the memory allocated to the dom0 and all domUs must be less
1.33      gdt       661: than the available memory.
                    662: 
                    663: Xen also provides a "balloon" driver, which can be used to let domains
                    664: use more memory temporarily.  TODO: Explain better, and explain how
                    665: well it works with NetBSD.
1.28      gdt       666: 
                    667: Virtual disks
                    668: -------------
                    669: 
1.33      gdt       670: With the file/vnd style, typically one creates a directory,
                    671: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
                    672: domUs.  Then, for each domU disk, one writes zeros to a file that then
                    673: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
                    674: for the first virtual disk for the domU called foo.  Writing zeros to
                    675: the file serves two purposes.  One is that preallocating the contents
                    676: improves performance.  The other is that vnd on sparse files has
                    677: failed to work.  TODO: give working/notworking NetBSD versions for
                    678: sparse vnd.  Note that the use of file/vnd for Xen is not really
                    679: different than creating a file-backed virtual disk for some other
1.39      gdt       680: purpose, except that xentools handles the vnconfig commands.  To
                    681: create an empty 4G virtual disk, simply do
                    682: 
                    683:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
1.33      gdt       684: 
1.89      gdt       685: Do not use qemu-img-xen, because this will create sparse file.  There
                    686: have been recent (2015) reports of sparse vnd(4) devices causing
                    687: lockups, but there is apparently no PR.
                    688: 
1.33      gdt       689: With the lvm style, one creates logical devices.  They are then used
1.48      gdt       690: similarly to vnds.  TODO: Add an example with lvm.
                    691: 
                    692: In domU config files, the disks are defined as a sequence of 3-tuples.
                    693: The first element is "method:/path/to/disk".  Common methods are
                    694: "file:" for file-backed vnd. and "phy:" for something that is already
                    695: a (TODO: character or block) device.
                    696: 
                    697: The second element is an artifact of how virtual disks are passed to
                    698: Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
                    699: are given a device name to associate with the disk, and values like
                    700: "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
                    701: as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
                    702: second argument.  The name given is converted to a major/minor by
1.49      gdt       703: calling stat(2) on the name in /dev and this is passed to the domU.
                    704: In the general case, the dom0 and domU can be different operating
1.48      gdt       705: systems, and it is an unwarranted assumption that they have consistent
                    706: numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
                    707: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
1.49      gdt       708: for the second works fine and avoids this issue.  For a GNU/Linux
                    709: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
                    710: /dev/hda1.
1.48      gdt       711: 
                    712: The third element is "w" for writable disks, and "r" for read-only
                    713: disks.
1.28      gdt       714: 
                    715: Virtual Networking
                    716: ------------------
                    717: 
1.46      gdt       718: Xen provides virtual ethernets, each of which connects the dom0 and a
                    719: domU.  For each virtual network, there is an interface "xvifN.M" in
                    720: the dom0, and in domU index N, a matching interface xennetM (NetBSD
                    721: name).  The interfaces behave as if there is an Ethernet with two
                    722: adaptors connected.  From this primitive, one can construct various
                    723: configurations.  We focus on two common and useful cases for which
                    724: there are existing scripts: bridging and NAT.
1.28      gdt       725: 
1.48      gdt       726: With bridging (in the example above), the domU perceives itself to be
                    727: on the same network as the dom0.  For server virtualization, this is
                    728: usually best.  Bridging is accomplished by creating a bridge(4) device
                    729: and adding the dom0's physical interface and the various xvifN.0
                    730: interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
                    731: config file.  The bridge must be set up already in the dom0; an
                    732: example /etc/ifconfig.bridge0 is:
1.46      gdt       733: 
                    734:         create
                    735:         up
                    736:         !brconfig bridge0 add wm0
1.28      gdt       737: 
                    738: With NAT, the domU perceives itself to be behind a NAT running on the
                    739: dom0.  This is often appropriate when running Xen on a workstation.
1.48      gdt       740: TODO: NAT appears to be configured by "vif = [ '' ]".
1.28      gdt       741: 
1.49      gdt       742: The MAC address specified is the one used for the interface in the new
1.53      gdt       743: domain.  The interface in dom0 will use this address XOR'd with
1.49      gdt       744: 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
                    745: 
1.33      gdt       746: Sizing domains
                    747: --------------
                    748: 
                    749: Modern x86 hardware has vast amounts of resources.  However, many
                    750: virtual servers can function just fine on far less.  A system with
                    751: 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is
                    752: far easier to adjust virtual resources than physical ones.  For
                    753: memory, it's just a config file edit and a reboot.  For disk, one can
                    754: create a new file and vnconfig it (or lvm), and then dump/restore,
                    755: just like updating physical disks, but without having to be there and
                    756: without those pesky connectors.
                    757: 
1.48      gdt       758: Starting domains automatically
                    759: ------------------------------
1.28      gdt       760: 
1.48      gdt       761: To start domains foo at bar at boot and shut them down cleanly on dom0
                    762: shutdown, in rc.conf add:
1.28      gdt       763: 
1.48      gdt       764:         xendomains="foo bar"
1.28      gdt       765: 
1.86      gdt       766: Note that earlier versions of the xentools41 xendomains rc.d scripth
                    767: usd xl, when one should use xm with 4.1.
1.28      gdt       768: 
                    769: Creating specific unprivileged domains (domU)
                    770: =============================================
1.14      gdt       771: 
                    772: Creating domUs is almost entirely independent of operating system.  We
1.49      gdt       773: have already presented the basics of config files.  Note that you must
                    774: have already completed the dom0 setup so that "xl list" (or "xm list")
                    775: works.
1.14      gdt       776: 
                    777: Creating an unprivileged NetBSD domain (domU)
                    778: ---------------------------------------------
1.1       mspo      779: 
1.49      gdt       780: See the earlier config file, and adjust memory.  Decide on how much
                    781: storage you will provide, and prepare it (file or lvm).
                    782: 
                    783: While the kernel will be obtained from the dom0 filesystem, the same
                    784: file should be present in the domU as /netbsd so that tools like
                    785: savecore(8) can work.   (This is helpful but not necessary.)
                    786: 
                    787: The kernel must be specifically for Xen and for use as a domU.  The
                    788: i386 and amd64 provide the following kernels:
                    789: 
                    790:         i386 XEN3_DOMU
                    791:         i386 XEN3PAE_DOMU
1.95      gdt       792:         amd64 XEN3_DOMU
1.5       mspo      793: 
1.49      gdt       794: Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
                    795: use the PAE version of the i386 kernel.
                    796: 
                    797: This will boot NetBSD, but this is not that useful if the disk is
                    798: empty.  One approach is to unpack sets onto the disk outside of xen
                    799: (by mounting it, just as you would prepare a physical disk for a
                    800: system you can't run the installer on).
                    801: 
                    802: A second approach is to run an INSTALL kernel, which has a miniroot
                    803: and can load sets from the network.  To do this, copy the INSTALL
                    804: kernel to / and change the kernel line in the config file to:
1.5       mspo      805: 
1.49      gdt       806:         kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
1.5       mspo      807: 
1.49      gdt       808: Then, start the domain as "xl create -c configname".
1.1       mspo      809: 
1.49      gdt       810: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
                    811: line should be used in the config file.
1.1       mspo      812: 
1.3       mspo      813:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
1.1       mspo      814: 
                    815: After booting the domain, the option to install via CDROM may be
1.49      gdt       816: selected.  The CDROM device should be changed to `xbd1d`.
1.1       mspo      817: 
1.49      gdt       818: Once done installing, "halt -p" the new domain (don't reboot or halt,
                    819: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
                    820: config file), switch the config file back to the XEN3_DOMU kernel,
                    821: and start the new domain again. Now it should be able to use "root on
                    822: xbd0a" and you should have a, functional NetBSD domU.
1.1       mspo      823: 
1.49      gdt       824: TODO: check if this is still accurate.
1.1       mspo      825: When the new domain is booting you'll see some warnings about *wscons*
                    826: and the pseudo-terminals. These can be fixed by editing the files
1.5       mspo      827: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
                    828: `/etc/ttys`, except *console*, like this:
1.1       mspo      829: 
1.3       mspo      830:     console "/usr/libexec/getty Pc"         vt100   on secure
                    831:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
                    832:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
                    833:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
                    834:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
1.1       mspo      835: 
1.5       mspo      836: Finally, all screens must be commented out from `/etc/wscons.conf`.
1.1       mspo      837: 
                    838: It is also desirable to add
                    839: 
1.49      gdt       840:         powerd=YES
1.1       mspo      841: 
1.5       mspo      842: in rc.conf. This way, the domain will be properly shut down if
1.53      gdt       843: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
1.1       mspo      844: 
1.92      gdt       845: It is not strictly necessary to have a kernel (as /netbsd) in the domU
                    846: filesystem.  However, various programs (e.g. netstat) will use that
                    847: kernel to look up symbols to read from kernel virtual memory.  If
                    848: /netbsd is not the running kernel, those lookups will fail.  (This is
                    849: not really a Xen-specific issue, but because the domU kernel is
                    850: obtained from the dom0, it is far more likely to be out of sync or
                    851: missing with Xen.)
                    852: 
1.14      gdt       853: Creating an unprivileged Linux domain (domU)
1.5       mspo      854: --------------------------------------------
1.1       mspo      855: 
                    856: Creating unprivileged Linux domains isn't much different from
                    857: unprivileged NetBSD domains, but there are some details to know.
                    858: 
                    859: First, the second parameter passed to the disk declaration (the '0x1' in
                    860: the example below)
                    861: 
1.3       mspo      862:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
1.1       mspo      863: 
                    864: does matter to Linux. It wants a Linux device number here (e.g. 0x300
1.49      gdt       865: for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
                    866: So, hda1 which has major 3 and minor 1 on a Linux system will have
                    867: device number 0x301.  Alternatively, devices names can be used (hda,
                    868: hdb, ...)  as xentools has a table to map these names to devices
                    869: numbers.  To export a partition to a Linux guest we can use:
1.1       mspo      870: 
1.49      gdt       871:         disk = [ 'phy:/dev/wd0e,0x300,w' ]
                    872:         root = "/dev/hda1 ro"
1.1       mspo      873: 
                    874: and it will appear as /dev/hda on the Linux system, and be used as root
                    875: partition.
                    876: 
1.49      gdt       877: To install the Linux system on the partition to be exported to the
                    878: guest domain, the following method can be used: install
                    879: sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
                    880: that will be the root partition of your Linux domain, and mount it.
                    881: Then copy the files from a working Linux system, make adjustments in
                    882: `/etc` (fstab, network config).  It should also be possible to extract
                    883: binary packages such as .rpm or .deb directly to the mounted partition
                    884: using the appropriate tool, possibly running under NetBSD's Linux
                    885: emulation.  Once the filesystem has been populated, umount it.  If
                    886: desirable, the filesystem can be converted to ext3 using tune2fs -j.
                    887: It should now be possible to boot the Linux guest domain, using one of
                    888: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
1.1       mspo      889: 
                    890: To get the linux console right, you need to add:
                    891: 
1.3       mspo      892:     extra = "xencons=tty1"
1.1       mspo      893: 
                    894: to your configuration since not all linux distributions auto-attach a
                    895: tty to the xen console.
                    896: 
1.14      gdt       897: Creating an unprivileged Solaris domain (domU)
1.5       mspo      898: ----------------------------------------------
1.1       mspo      899: 
1.50      gdt       900: See possibly outdated
                    901: [Solaris domU instructions](/ports/xen/howto-solaris/).
1.5       mspo      902: 
1.1       mspo      903: 
1.52      gdt       904: PCI passthrough: Using PCI devices in guest domains
                    905: ---------------------------------------------------
1.1       mspo      906: 
1.53      gdt       907: The dom0 can give other domains access to selected PCI
1.52      gdt       908: devices. This can allow, for example, a non-privileged domain to have
                    909: access to a physical network interface or disk controller.  However,
                    910: keep in mind that giving a domain access to a PCI device most likely
                    911: will give the domain read/write access to the whole physical memory,
                    912: as PCs don't have an IOMMU to restrict memory access to DMA-capable
1.53      gdt       913: device.  Also, it's not possible to export ISA devices to non-dom0
1.52      gdt       914: domains, which means that the primary VGA adapter can't be exported.
                    915: A guest domain trying to access the VGA registers will panic.
                    916: 
1.53      gdt       917: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
1.52      gdt       918: not been ported to later versions at this time.
                    919: 
                    920: For a PCI device to be exported to a domU, is has to be attached to
                    921: the "pciback" driver in dom0.  Devices passed to the dom0 via the
                    922: pciback.hide boot parameter will attach to "pciback" instead of the
                    923: usual driver.  The list of devices is specified as "(bus:dev.func)",
1.5       mspo      924: where bus and dev are 2-digit hexadecimal numbers, and func a
                    925: single-digit number:
1.1       mspo      926: 
1.52      gdt       927:         pciback.hide=(00:0a.0)(00:06.0)
1.1       mspo      928: 
1.52      gdt       929: pciback devices should show up in the dom0's boot messages, and the
1.5       mspo      930: devices should be listed in the `/kern/xen/pci` directory.
1.1       mspo      931: 
1.52      gdt       932: PCI devices to be exported to a domU are listed in the "pci" array of
                    933: the domU's config file, with the format "0000:bus:dev.func".
1.1       mspo      934: 
1.52      gdt       935:         pci = [ '0000:00:06.0', '0000:00:0a.0' ]
1.1       mspo      936: 
1.52      gdt       937: In the domU an "xpci" device will show up, to which one or more pci
                    938: busses will attach.  Then the PCI drivers will attach to PCI busses as
                    939: usual.  Note that the default NetBSD DOMU kernels do not have "xpci"
                    940: or any PCI drivers built in by default; you have to build your own
                    941: kernel to use PCI devices in a domU.  Here's a kernel config example;
                    942: note that only the "xpci" lines are unusual.
                    943: 
                    944:         include         "arch/i386/conf/XEN3_DOMU"
                    945: 
                    946:         # Add support for PCI busses to the XEN3_DOMU kernel
                    947:         xpci* at xenbus ?
                    948:         pci* at xpci ?
                    949: 
                    950:         # PCI USB controllers
                    951:         uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
                    952: 
                    953:         # USB bus support
                    954:         usb*    at uhci?
                    955: 
                    956:         # USB Hubs
                    957:         uhub*   at usb?
                    958:         uhub*   at uhub? port ? configuration ? interface ?
                    959: 
                    960:         # USB Mass Storage
                    961:         umass*  at uhub? port ? configuration ? interface ?
                    962:         wd*     at umass?
                    963:         # SCSI controllers
                    964:         ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
                    965: 
                    966:         # SCSI bus support (for both ahc and umass)
                    967:         scsibus* at scsi?
                    968: 
                    969:         # SCSI devices
                    970:         sd*     at scsibus? target ? lun ?      # SCSI disk drives
                    971:         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
1.1       mspo      972: 
                    973: 
1.28      gdt       974: NetBSD as a domU in a VPS
                    975: =========================
                    976: 
                    977: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
                    978: hardware.  This section explains how to deal with Xen in a domU as a
                    979: virtual private server where you do not control or have access to the
1.70      gdt       980: dom0.  This is not intended to be an exhaustive list of VPS providers;
                    981: only a few are mentioned that specifically support NetBSD.
1.28      gdt       982: 
1.52      gdt       983: VPS operators provide varying degrees of access and mechanisms for
                    984: configuration.  The big issue is usually how one controls which kernel
                    985: is booted, because the kernel is nominally in the dom0 filesystem (to
1.70      gdt       986: which VPS users do not normally have acesss).  A second issue is how
                    987: to install NetBSD.
1.52      gdt       988: A VPS user may want to compile a kernel for security updates, to run
                    989: npf, run IPsec, or any other reason why someone would want to change
                    990: their kernel.
                    991: 
                    992: One approach is to have an adminstrative interface to upload a kernel,
1.68      gdt       993: or to select from a prepopulated list.  Other approaches are pygrub
1.59      gdt       994: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
                    995: kernel from the domU filesystem.  This is closer to a regular physical
                    996: computer, where someone who controls a machine can replace the kernel.
1.52      gdt       997: 
1.74      gdt       998: A second issue is multiple CPUs.  With NetBSD 6, domUs support
                    999: multiple vcpus, and it is typical for VPS providers to enable multiple
                   1000: CPUs for NetBSD domUs.
                   1001: 
1.68      gdt      1002: pygrub
1.59      gdt      1003: -------
1.52      gdt      1004: 
1.68      gdt      1005: pygrub runs in the dom0 and looks into the domU filesystem.  This
1.59      gdt      1006: implies that the domU must have a kernel in a filesystem in a format
1.68      gdt      1007: known to pygrub.  As of 2014, pygrub seems to be of mostly historical
                   1008: interest.
1.52      gdt      1009: 
1.59      gdt      1010: pvgrub
                   1011: ------
                   1012: 
                   1013: pvgrub is a version of grub that uses PV operations instead of BIOS
                   1014: calls.  It is booted from the dom0 as the domU kernel, and then reads
                   1015: /grub/menu.lst and loads a kernel from the domU filesystem.
                   1016: 
1.70      gdt      1017: [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
1.71      gdt      1018: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
                   1019: (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
1.70      gdt      1020: page](http://www.panix.com/v-colo/grub.html), which describes only
1.74      gdt      1021: Linux but should be updated to cover NetBSD :-).
1.70      gdt      1022: 
                   1023: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
                   1024: their own kernel.  See then [prgmr.com NetBSD
1.74      gdt      1025: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
                   1026: (which is in need of updating).
1.59      gdt      1027: 
1.70      gdt      1028: It appears that [grub's FFS
                   1029: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
                   1030: does not support all aspects of modern FFS, but there are also reports
1.72      gdt      1031: that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT
1.70      gdt      1032: partition for the kernel with the intent that grub can understand it,
                   1033: which leads to /netbsd not being the actual kernel.  One must remember
                   1034: to update the special boot partiion.
1.59      gdt      1035: 
                   1036: Amazon
                   1037: ------
                   1038: 
1.95      gdt      1039: See the [Amazon EC2 page](../amazon_ec2/).
1.44      gdt      1040: 
                   1041: Using npf
                   1042: ---------
                   1043: 
1.81      gdt      1044: In standard kernels, npf is a module, and thus cannot be loaded in a
1.44      gdt      1045: DOMU kernel.
                   1046: 
1.95      gdt      1047: TODO: Explain how to compile npf into a custom kernel, answering (but
                   1048: note that the problem was caused by not booting the right kernel)
                   1049: [this email to
                   1050: netbsd-users](http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html).
1.65      gdt      1051: 
                   1052: TODO items for improving NetBSD/xen
                   1053: ===================================
                   1054: 
1.93      gdt      1055: * Make the NetBSD dom0 kernel work with SMP.
                   1056: * Test the Xen 4.5 packages adequately to be able to recommend them as
                   1057:   the standard approach.
                   1058: * Get PCI passthrough working on Xen 4.5
1.65      gdt      1059: * Get pvgrub into pkgsrc, either via xentools or separately.
                   1060: * grub
1.70      gdt      1061:   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary
1.66      gdt      1062:     fragsize/blocksize (UFS2 support may be present; the point is to
                   1063:     make it so that with any UFS1/UFS2 filesystem setup that works
                   1064:     with NetBSD grub will also work).
1.70      gdt      1065:     See [pkg/40258](http://gnats.netbsd.org/40258).
1.65      gdt      1066:   * Push patches upstream.
                   1067:   * Get UFS2 patches into pvgrub.
                   1068: * Add support for PV ops to a version of /boot, and make it usable as
                   1069:   a kernel in Xen, similar to pvgrub.
1.93      gdt      1070: * Solve somehow the issue with modules for GENERIC not being loadable
                   1071:   in a Xen dom0 or domU kernel.
                   1072: 
                   1073: Random pointers
                   1074: ===============
                   1075: 
                   1076: TODO: This section contains links from elsewhere not yet integrated
                   1077: into the HOWTO.
                   1078: 
                   1079: * http://www.lumbercartel.ca/library/xen/
                   1080: * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html

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