Annotation of wikisrc/ports/xen/howto.mdwn, revision 1.102

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: 
1.102   ! gdt        84: xenkernel3 provides Xen 3.1.  This no longer receives security patches
        !            85: and should not be used.  It supports PCI passthrough, which is why
        !            86: people use it anyway. Xen 3.1 supports non-PAE on i386.
        !            87: 
        !            88: xenkernel33 provides Xen 3.3.  This no longer receives security
        !            89: patches and should not be used.  Xen 3.3 supports non-PAE on i386.
1.15      gdt        90: 
                     91: xenkernel41 provides Xen 4.1.  This is no longer maintained by Xen,
1.102   ! gdt        92: but as of 2014-12 receives backported security patches.  There are no
        !            93: good reasons to run this version.  reasonable although trailing-edge
        !            94: choice.
        !            95: 
        !            96: xenkernel42 provides Xen 4.2. This is no longer maintained by Xen, but
        !            97: as of 2014-12 receives backported security patches.  The only reason
        !            98: to run this is if you need to use xm instead of xl.
1.15      gdt        99: 
1.102   ! gdt       100: xenkernel45 provides Xen 4.5.  This is new to pkgsrc as of 2015-01 and
        !           101: recommended for use as a conservative choice.
1.15      gdt       102: 
1.102   ! gdt       103: xenkernel46 provides Xen 4.6.  TODO: Probably this is the recommended
        !           104: version.
1.85      gdt       105: 
1.96      gdt       106: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/).
                    107: 
1.15      gdt       108: Ideally newer versions of Xen will be added to pkgsrc.
                    109: 
1.85      gdt       110: Note that NetBSD support is called XEN3.  It works with Xen 3 and Xen
                    111: 4 because the hypercall interface has been stable.
1.20      gdt       112: 
1.19      gdt       113: Xen command program
                    114: -------------------
                    115: 
1.79      gdt       116: Early Xen used a program called xm to manipulate the system from the
1.19      gdt       117: dom0.  Starting in 4.1, a replacement program with similar behavior
1.79      gdt       118: called xl is provided, but it does not work well in 4.1.  In 4.2, both
                    119: xm and xl work fine.  4.4 is the last version that has xm.  You must
                    120: choose one or the other, because it affects which daemons you run.
1.19      gdt       121: 
1.15      gdt       122: NetBSD
                    123: ------
                    124: 
                    125: The netbsd-5, netbsd-6, netbsd-7, and -current branches are all
                    126: reasonable choices, with more or less the same considerations for
                    127: non-Xen use.  Therefore, netbsd-6 is recommended as the stable version
1.29      gdt       128: of the most recent release for production use.  For those wanting to
                    129: learn Xen or without production stability concerns, netbsd-7 is likely
                    130: most appropriate.
1.15      gdt       131: 
                    132: As of NetBSD 6, a NetBSD domU will support multiple vcpus.  There is
                    133: no SMP support for NetBSD as dom0.  (The dom0 itself doesn't really
                    134: need SMP; the lack of support is really a problem when using a dom0 as
                    135: a normal computer.)
                    136: 
1.18      gdt       137: Architecture
                    138: ------------
                    139: 
1.29      gdt       140: Xen itself can run on i386 or amd64 machines.  (Practically, almost
1.99      gdt       141: any computer where one would want to run Xen today supports amd64.)
                    142: 
                    143: Xen, the dom0 kernel, and each domU kernel can be either i386 or
                    144: amd64.  When building a xenkernel package, one obtains i386 on an i386
                    145: host, and amd64 on an amd64 host.  If the xen kernel is i386, then the
                    146: dom0 kernel and all domU kernels must be i386.  With an amd64 xen
                    147: kernel, an amd64 dom0 kernel is known to work, and an i386 dom0 kernel
                    148: should in theory work.  An amd64 xen/dom0 is known to support both
                    149: i386 and amd64 domUs.
                    150: 
1.101     gdt       151: i386 dom0 and domU kernels must be PAE (except for Xen 3.1); these are
                    152: built by default.  (Note that emacs (at least) fails if run on i386
                    153: with PAE when built without, and vice versa, presumably due to bugs in
                    154: the undump code.)
1.99      gdt       155: 
                    156: Because of the above, the standard approach is to use amd64 for the
                    157: dom0.
1.29      gdt       158: 
                    159: Xen 4.2 is the last version to support i386 as a host.  TODO: Clarify
1.100     gdt       160: if this is about the CPU, the xen kernel, or the dom0 kernel having to
                    161: be amd64.
                    162: 
1.29      gdt       163: 
1.89      gdt       164: Stability
                    165: ---------
                    166: 
                    167: Mostly, NetBSD as a dom0 or domU is quite stable.
                    168: However, there are some open PRs indicating problems.
                    169: 
1.91      gdt       170:  - [PR 48125](http://gnats.netbsd.org/48125)
                    171:  - [PR 47720](http://gnats.netbsd.org/47720)
1.89      gdt       172: 
                    173: Note also that there are issues with sparse vnd(4) instances, but
                    174: these are not about Xen.
                    175: 
1.15      gdt       176: Recommendation
                    177: --------------
                    178: 
1.18      gdt       179: Therefore, this HOWTO recommends running xenkernel42 (and xentools42),
1.30      gdt       180: xl, the NetBSD 6 stable branch, and to use an amd64 kernel as the
                    181: dom0.  Either the i386 or amd64 of NetBSD may be used as domUs.
1.15      gdt       182: 
1.36      gdt       183: Build problems
                    184: --------------
                    185: 
                    186: Ideally, all versions of Xen in pkgsrc would build on all versions of
                    187: NetBSD on both i386 and amd64.  However, that isn't the case.  Besides
                    188: aging code and aging compilers, qemu (included in xentools for HVM
1.62      gdt       189: support) is difficult to build.  The following are known to work or FAIL:
1.36      gdt       190: 
1.62      gdt       191:         xenkernel3 netbsd-5 amd64
1.63      gdt       192:         xentools3 netbsd-5 amd64
1.64      gdt       193:         xentools3=hvm netbsd-5 amd64 ????
1.62      gdt       194:         xenkernel33 netbsd-5 amd64
1.63      gdt       195:         xentools33 netbsd-5 amd64
1.36      gdt       196:         xenkernel41 netbsd-5 amd64
                    197:         xentools41 netbsd-5 amd64
1.62      gdt       198:         xenkernel42 netbsd-5 amd64
1.64      gdt       199:         xentools42 netbsd-5 amd64
1.62      gdt       200: 
                    201:         xenkernel3 netbsd-6 i386 FAIL
                    202:         xentools3 netbsd-6 i386
1.63      gdt       203:         xentools3-hvm netbsd-6 i386 FAIL (dependencies fail)
                    204:         xenkernel33 netbsd-6 i386
                    205:         xentools33 netbsd-6 i386
1.36      gdt       206:         xenkernel41 netbsd-6 i386
                    207:         xentools41 netbsd-6 i386
1.63      gdt       208:         xenkernel42 netbsd-6 i386
1.64      gdt       209:         xentools42 netbsd-6 i386 *MIXED
                    210: 
1.69      gdt       211:        (all 3 and 33 seem to FAIL)
                    212:         xenkernel41 netbsd-7 i386
                    213:         xentools41 netbsd-7 i386
                    214:         xenkernel42 netbsd-7 i386
                    215:         xentools42 netbsd-7 i386 ??FAIL
                    216: 
1.64      gdt       217: (*On netbsd-6 i386, there is a xentools42 in the 2014Q3 official builds,
                    218: but it does not build for gdt.)
1.36      gdt       219: 
1.15      gdt       220: NetBSD as a dom0
                    221: ================
                    222: 
                    223: NetBSD can be used as a dom0 and works very well.  The following
                    224: sections address installation, updating NetBSD, and updating Xen.
1.19      gdt       225: Note that it doesn't make sense to talk about installing a dom0 OS
                    226: without also installing Xen itself.  We first address installing
                    227: NetBSD, which is not yet a dom0, and then adding Xen, pivoting the
                    228: NetBSD install to a dom0 install by just changing the kernel and boot
                    229: configuration.
1.15      gdt       230: 
1.45      gdt       231: For experimenting with Xen, a machine with as little as 1G of RAM and
                    232: 100G of disk can work.  For running many domUs in productions, far
                    233: more will be needed.
                    234: 
1.15      gdt       235: Styles of dom0 operation
                    236: ------------------------
                    237: 
                    238: There are two basic ways to use Xen.  The traditional method is for
                    239: the dom0 to do absolutely nothing other than providing support to some
                    240: number of domUs.  Such a system was probably installed for the sole
                    241: purpose of hosting domUs, and sits in a server room on a UPS.
                    242: 
                    243: The other way is to put Xen under a normal-usage computer, so that the
                    244: dom0 is what the computer would have been without Xen, perhaps a
                    245: desktop or laptop.  Then, one can run domUs at will.  Purists will
                    246: deride this as less secure than the previous approach, and for a
                    247: computer whose purpose is to run domUs, they are right.  But Xen and a
1.93      gdt       248: dom0 (without domUs) is not meaningfully less secure than the same
1.15      gdt       249: things running without Xen.  One can boot Xen or boot regular NetBSD
                    250: alternately with little problems, simply refraining from starting the
                    251: Xen daemons when not running Xen.
                    252: 
                    253: Note that NetBSD as dom0 does not support multiple CPUs.  This will
1.51      gdt       254: limit the performance of the Xen/dom0 workstation approach.  In theory
                    255: the only issue is that the "backend drivers" are not yet MPSAFE:
                    256:   http://mail-index.netbsd.org/netbsd-users/2014/08/29/msg015195.html
1.15      gdt       257: 
1.19      gdt       258: Installation of NetBSD
                    259: ----------------------
1.13      gdt       260: 
1.19      gdt       261: First,
1.27      jnemeth   262: [install NetBSD/amd64](/guide/inst/)
1.19      gdt       263: just as you would if you were not using Xen.
                    264: However, the partitioning approach is very important.
                    265: 
                    266: If you want to use RAIDframe for the dom0, there are no special issues
                    267: for Xen.  Typically one provides RAID storage for the dom0, and the
1.22      gdt       268: domU systems are unaware of RAID.  The 2nd-stage loader bootxx_* skips
                    269: over a RAID1 header to find /boot from a filesystem within a RAID
                    270: partition; this is no different when booting Xen.
1.19      gdt       271: 
                    272: There are 4 styles of providing backing storage for the virtual disks
1.93      gdt       273: used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN.
1.19      gdt       274: 
                    275: With raw partitions, one has a disklabel (or gpt) partition sized for
                    276: each virtual disk to be used by the domU.  (If you are able to predict
                    277: how domU usage will evolve, please add an explanation to the HOWTO.
                    278: Seriously, needs tend to change over time.)
                    279: 
1.27      jnemeth   280: One can use [lvm(8)](/guide/lvm/) to create logical devices to use
                    281: for domU disks.  This is almost as efficient as raw disk partitions
                    282: and more flexible.  Hence raw disk partitions should typically not
                    283: be used.
1.19      gdt       284: 
                    285: One can use files in the dom0 filesystem, typically created by dd'ing
                    286: /dev/zero to create a specific size.  This is somewhat less efficient,
                    287: but very convenient, as one can cp the files for backup, or move them
                    288: between dom0 hosts.
                    289: 
                    290: Finally, in theory one can place the files backing the domU disks in a
                    291: SAN.  (This is an invitation for someone who has done this to add a
                    292: HOWTO page.)
1.1       mspo      293: 
1.19      gdt       294: Installation of Xen
                    295: -------------------
1.1       mspo      296: 
1.20      gdt       297: In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from
                    298: pkgsrc (or another matching pair).
                    299: See [the pkgsrc
                    300: documentation](http://www.NetBSD.org/docs/pkgsrc/) for help with pkgsrc.
                    301: 
                    302: For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More
                    303: recent versions have HVM support integrated in the main xentools
                    304: package.  It is entirely reasonable to run only PV guests.
                    305: 
                    306: Next you need to install the selected Xen kernel itself, which is
                    307: installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.
                    308: For debugging, one may copy xen-debug.gz; this is conceptually similar
                    309: to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only
                    310: useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel
                    311: in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz
1.75      gdt       312: of a NetBSD build.  If using i386, use
                    313: releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  (If using Xen
                    314: 3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen.  But you
                    315: should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and
                    316: typically are) left compressed.
                    317: 
                    318: In a dom0 kernel, kernfs is mandatory for xend to comunicate with the
                    319: kernel, so ensure that /kern is in fstab.  TODO: Say this is default,
                    320: or file a PR and give a reference.
1.20      gdt       321: 
                    322: Because you already installed NetBSD, you have a working boot setup
                    323: with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the
                    324: beginning of your root filesystem, /boot present, and likely
                    325: /boot.cfg.  (If not, fix before continuing!)
                    326: 
1.76      gdt       327: Add a line to to /boot.cfg to boot Xen.  See boot.cfg(5) for an
                    328: example.  The basic line is
1.20      gdt       329: 
1.37      gdt       330:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
1.20      gdt       331: 
                    332: which specifies that the dom0 should have 256M, leaving the rest to be
1.77      gdt       333: allocated for domUs.  To use a serial console, use
                    334: 
                    335:         menu=Xen:load /netbsd-XEN3_DOM0.gz console=com0;multiboot /xen.gz dom0_mem=256M console=com1 com1=9600,8n1
                    336: 
                    337: which will use the first serial port for Xen (which counts starting
                    338: from 1), forcing speed/parity, and also for NetBSD (which counts
                    339: starting at 0).  In an attempt to add performance, one can also add
1.37      gdt       340: 
                    341:         dom0_max_vcpus=1 dom0_vcpus_pin
                    342: 
                    343: to force only one vcpu to be provided (since NetBSD dom0 can't use
                    344: more) and to pin that vcpu to a physical cpu.  TODO: benchmark this.
1.20      gdt       345: 
1.93      gdt       346: Xen has [many boot
                    347: options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),
                    348: and other tham dom0 memory and max_vcpus, they are generally not
                    349: necessary.
                    350: 
1.20      gdt       351: As with non-Xen systems, you should have a line to boot /netbsd (a
                    352: kernel that works without Xen) and fallback versions of the non-Xen
                    353: kernel, Xen, and the dom0 kernel.
1.1       mspo      354: 
1.76      gdt       355: Now, reboot so that you are running a DOM0 kernel under Xen, rather
                    356: than GENERIC without Xen.
                    357: 
1.54      gdt       358: Using grub (historic)
                    359: ---------------------
                    360: 
                    361: Before NetBSD's native bootloader could support Xen, the use of
                    362: grub was recommended.  If necessary, see the
                    363: [old grub information](/ports/xen/howto-grub/).
                    364: 
1.28      gdt       365: The [HowTo on Installing into
                    366: RAID-1](http://mail-index.NetBSD.org/port-xen/2006/03/01/0010.html)
                    367: explains how to set up booting a dom0 with Xen using grub with
                    368: NetBSD's RAIDframe.  (This is obsolete with the use of NetBSD's native
                    369: boot.)
                    370: 
1.21      gdt       371: Configuring Xen
                    372: ---------------
                    373: 
1.53      gdt       374: Xen logs will be in /var/log/xen.
                    375: 
1.76      gdt       376: Now, you have a system that will boot Xen and the dom0 kernel, but not
                    377: do anything else special.  Make sure that you have rebooted into Xen.
                    378: There will be no domUs, and none can be started because you still have
1.102   ! gdt       379: to configure the dom0 daemons.
1.21      gdt       380: 
1.102   ! gdt       381: The daemons which should be run vary with Xen version and with whether
        !           382: one is using xm or xl.  The Xen 3.1 and 3.3 packages use xm.  Xen 4.1
        !           383: and higher packages use xl.  While is is possible to use xm with some
        !           384: 4.x versions (TODO: 4.1 and 4.2?), the pkgsrc-provided rc.d scripts do
        !           385: not support this as of 2014-12-26, and thus the HOWTO does not support
        !           386: it either.  (Make sure your packages are reasonably recent.)
1.43      gdt       387: 
1.102   ! gdt       388: For "xm" (3.1 and 3.3), you should enable xend and xenbackendd (but
        !           389: note that you should be using 4.x):
1.31      gdt       390: 
1.32      gdt       391:         xend=YES
                    392:         xenbackendd=YES
1.31      gdt       393: 
1.102   ! gdt       394: For "xl" (4.x), you should enabled xend and xencommons (xenstored).
        !           395: Trying to boot 4.x without xencommons=YES will result in a hang; it is
        !           396: necessary to hig ^C on the console to let the machine finish booting.
        !           397: TODO: explain why xend is installed by the package.
1.31      gdt       398: 
1.53      gdt       399:         xencommons=YES
1.31      gdt       400: 
1.102   ! gdt       401: The installation of NetBSD should already have created devices for xen
        !           402: (xencons, xenevt), but if they are not present, create them:
1.31      gdt       403: 
1.102   ! gdt       404:         cd /dev && sh MAKEDEV xen
1.86      gdt       405: 
1.31      gdt       406: TODO: Recommend for/against xen-watchdog.
1.27      jnemeth   407: 
1.53      gdt       408: After you have configured the daemons and either started them (in the
1.79      gdt       409: order given) or rebooted, use xm or xl to inspect Xen's boot messages,
1.102   ! gdt       410: available resources, and running domains.  An example with xl follows:
1.34      gdt       411: 
1.102   ! gdt       412:         # xl dmesg
1.43      gdt       413:        [xen's boot info]
1.102   ! gdt       414:         # xl info
1.43      gdt       415:        [available memory, etc.]
1.102   ! gdt       416:         # xl list
1.43      gdt       417:         Name              Id  Mem(MB)  CPU  State  Time(s)  Console
                    418:         Domain-0           0       64    0  r----     58.1
1.33      gdt       419: 
1.88      gdt       420: ### Issues with xencommons
                    421: 
                    422: xencommons starts xenstored, which stores data on behalf of dom0 and
                    423: domUs.  It does not currently work to stop and start xenstored.
                    424: Certainly all domUs should be shutdown first, following the sort order
                    425: of the rc.d scripts.  However, the dom0 sets up state with xenstored,
                    426: and is not notified when xenstored exits, leading to not recreating
                    427: the state when the new xenstored starts.  Until there's a mechanism to
                    428: make this work, one should not expect to be able to restart xenstored
                    429: (and thus xencommons).  There is currently no reason to expect that
                    430: this will get fixed any time soon.
                    431: 
1.41      gdt       432: anita (for testing NetBSD)
                    433: --------------------------
                    434: 
1.82      gdt       435: With the setup so far (assuming 4.2/xl), one should be able to run
                    436: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
                    437: root, because anita must create a domU):
                    438: 
                    439:         anita --vmm=xl test file:///usr/obj/i386/
                    440: 
                    441: Alternatively, one can use --vmm=xm to use xm-based domU creation
                    442: instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.
                    443:     
1.40      gdt       444: Xen-specific NetBSD issues
                    445: --------------------------
                    446: 
                    447: There are (at least) two additional things different about NetBSD as a
                    448: dom0 kernel compared to hardware.
                    449: 
                    450: One is that modules are not usable in DOM0 kernels, so one must
                    451: compile in what's needed.  It's not really that modules cannot work,
                    452: but that modules must be built for XEN3_DOM0 because some of the
                    453: defines change and the normal module builds don't do this.  Basically,
                    454: enabling Xen changes the kernel ABI, and the module build system
                    455: doesn't cope with this.
                    456: 
                    457: The other difference is that XEN3_DOM0 does not have exactly the same
                    458: options as GENERIC.  While it is debatable whether or not this is a
                    459: bug, users should be aware of this and can simply add missing config
                    460: items if desired.
                    461: 
1.15      gdt       462: Updating NetBSD in a dom0
                    463: -------------------------
                    464: 
                    465: This is just like updating NetBSD on bare hardware, assuming the new
                    466: version supports the version of Xen you are running.  Generally, one
                    467: replaces the kernel and reboots, and then overlays userland binaries
                    468: and adjusts /etc.
                    469: 
                    470: Note that one must update both the non-Xen kernel typically used for
                    471: rescue purposes and the DOM0 kernel used with Xen.
                    472: 
1.55      gdt       473: Converting from grub to /boot
                    474: -----------------------------
                    475: 
                    476: These instructions were [TODO: will be] used to convert a system from
                    477: grub to /boot.  The system was originally installed in February of
                    478: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated
                    479: over time.  Before these commands, it was running NetBSD 6 i386, Xen
                    480: 4.1 and grub, much like the message linked earlier in the grub
                    481: section.
                    482: 
                    483:         # Install mbr bootblocks on both disks. 
                    484:         fdisk -i /dev/rwd0d
                    485:         fdisk -i /dev/rwd1d
                    486:         # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components.
                    487:         installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1
                    488:         installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1
                    489:         # Install secondary boot loader
                    490:         cp -p /usr/mdec/boot /
                    491:         # Create boog.cfg following earlier guidance:
                    492:         menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=256M
                    493:         menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=256M
                    494:         menu=GENERIC:boot
                    495:         menu=GENERIC single-user:boot -s
                    496:         menu=GENERIC.ok:boot netbsd.ok
                    497:         menu=GENERIC.ok single-user:boot netbsd.ok -s
                    498:         menu=Drop to boot prompt:prompt
                    499:         default=1
                    500:         timeout=30
                    501: 
                    502: TODO: actually do this and fix it if necessary.
1.22      gdt       503: 
1.102   ! gdt       504: Upgrading Xen versions
1.15      gdt       505: ---------------------
                    506: 
1.21      gdt       507: Updating Xen is conceptually not difficult, but can run into all the
                    508: issues found when installing Xen.  Assuming migration from 4.1 to 4.2,
                    509: remove the xenkernel41 and xentools41 packages and install the
                    510: xenkernel42 and xentools42 packages.  Copy the 4.2 xen.gz to /.
                    511: 
1.102   ! gdt       512: Ensure that the contents of /etc/rc.d/xen* are correct.  Specifically,
        !           513: they must match the package you just installed and not be left over
        !           514: from some previous installation.
        !           515: 
        !           516: Enable the correct set of daemons; see the configuring section above.
        !           517: (Upgrading from 3.x to 4.x without doing this will result in a hang.)
        !           518: 
        !           519: Ensure that the domU config files are valid for the new version.
        !           520: Specifically: remove autorestart=True, and ensure that disks are
        !           521: specified with numbers as the second argument, as the examples above
        !           522: show, and not NetBSD device names.
1.15      gdt       523: 
1.97      gdt       524: Hardware known to work
                    525: ----------------------
                    526: 
                    527: Arguably, this section is misplaced, and there should be a page of
                    528: hardware that runs NetBSD/amd64 well, with the mostly-well-founded
                    529: assumption that NetBSD/xen runs fine on any modern hardware that
                    530: NetBSD/amd64 runs well on.  Until then, we give motherboard/CPU/RAM
                    531: triples to aid those choosing a motherboard.  Note that Xen systems
                    532: usually do not run X, so a listing here does not imply that X works at
                    533: all.
                    534: 
                    535:         Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC
                    536:         Supermicro ??, Atom C2758 (8 core), 32 GiB ECC
                    537:         ASUS M5A78L-M/USB3 AM3+ microATX, AMD Piledriver X8 4000MHz, 16 GiB ECC
                    538: 
                    539: Older hardware:
                    540: 
1.98      gdt       541:         Intel D915GEV, Pentium4 CPU 3.40GHz, 4GB 533MHz Synchronous DDR2
1.28      gdt       542: 
1.82      gdt       543: Running Xen under qemu
                    544: ----------------------
                    545: 
                    546: The astute reader will note that this section is somewhat twisted.
                    547: However, it can be useful to run Xen under qemu either because the
                    548: version of NetBSD as a dom0 does not run on the hardware in use, or to
                    549: generate automated test cases involving Xen.
                    550: 
1.84      gdt       551: In 2015-01, the following combination was reported to mostly work:
1.82      gdt       552: 
                    553:         host OS: NetBSD/amd64 6.1.4
                    554:         qemu: 2.2.0 from pkgsrc
                    555:         Xen kernel: xenkernel42-4.2.5nb1 from pkgsrc
                    556:         dom0 kernel: NetBSD/amd64 6.1.5
                    557:         Xen tools: xentools42-4.2.5 from pkgsrc
                    558: 
1.91      gdt       559: See [PR 47720](http://gnats.netbsd.org/47720) for a problem with dom0
                    560: shutdown.
1.84      gdt       561: 
1.28      gdt       562: Unprivileged domains (domU)
                    563: ===========================
                    564: 
                    565: This section describes general concepts about domUs.  It does not
1.33      gdt       566: address specific domU operating systems or how to install them.  The
                    567: config files for domUs are typically in /usr/pkg/etc/xen, and are
1.60      wiki      568: typically named so that the file name, domU name and the domU's host
1.33      gdt       569: name match.
                    570: 
                    571: The domU is provided with cpu and memory by Xen, configured by the
                    572: dom0.  The domU is provided with disk and network by the dom0,
                    573: mediated by Xen, and configured in the dom0.
                    574: 
                    575: Entropy in domUs can be an issue; physical disks and network are on
                    576: the dom0.  NetBSD's /dev/random system works, but is often challenged.
                    577: 
1.48      gdt       578: Config files
                    579: ------------
                    580: 
                    581: There is no good order to present config files and the concepts
                    582: surrounding what is being configured.  We first show an example config
                    583: file, and then in the various sections give details.
                    584: 
                    585: See (at least in xentools41) /usr/pkg/share/examples/xen/xmexample*,
                    586: for a large number of well-commented examples, mostly for running
                    587: GNU/Linux.
                    588: 
                    589: The following is an example minimal domain configuration file
                    590: "/usr/pkg/etc/xen/foo".  It is (with only a name change) an actual
                    591: known working config file on Xen 4.1 (NetBSD 5 amd64 dom0 and NetBSD 5
                    592: i386 domU).  The domU serves as a network file server.
                    593: 
                    594:         # -*- mode: python; -*-
                    595: 
                    596:         kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz"
                    597:         memory = 1024
                    598:         vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ]
                    599:         disk = [ 'file:/n0/xen/foo-wd0,0x0,w',
                    600:                  'file:/n0/xen/foo-wd1,0x1,w' ]
                    601: 
                    602: The domain will have the same name as the file.  The kernel has the
                    603: host/domU name in it, so that on the dom0 one can update the various
                    604: domUs independently.  The vif line causes an interface to be provided,
                    605: with a specific mac address (do not reuse MAC addresses!), in bridge
                    606: mode.  Two disks are provided, and they are both writable; the bits
                    607: are stored in files and Xen attaches them to a vnd(4) device in the
                    608: dom0 on domain creation.  The system treates xbd0 as the boot device
                    609: without needing explicit configuration.
                    610: 
                    611: By default xm looks for domain config files in /usr/pkg/etc/xen.  Note
                    612: that "xm create" takes the name of a config file, while other commands
                    613: take the name of a domain.  To create the domain, connect to the
                    614: console, create the domain while attaching the console, shutdown the
                    615: domain, and see if it has finished stopping, do (or xl with Xen >=
                    616: 4.2):
                    617: 
                    618:         xm create foo
                    619:         xm console foo
                    620:         xm create -c foo
                    621:         xm shutdown foo
1.90      gdt       622:         xm list
1.48      gdt       623: 
                    624: Typing ^] will exit the console session.  Shutting down a domain is
                    625: equivalent to pushing the power button; a NetBSD domU will receive a
                    626: power-press event and do a clean shutdown.  Shutting down the dom0
                    627: will trigger controlled shutdowns of all configured domUs.
                    628: 
                    629: domU kernels
                    630: ------------
                    631: 
                    632: On a physical computer, the BIOS reads sector 0, and a chain of boot
                    633: loaders finds and loads a kernel.  Normally this comes from the root
                    634: filesystem.  With Xen domUs, the process is totally different.  The
                    635: normal path is for the domU kernel to be a file in the dom0's
                    636: filesystem.  At the request of the dom0, Xen loads that kernel into a
                    637: new domU instance and starts execution.  While domU kernels can be
                    638: anyplace, reasonable places to store domU kernels on the dom0 are in /
                    639: (so they are near the dom0 kernel), in /usr/pkg/etc/xen (near the
                    640: config files), or in /u0/xen (where the vdisks are).
                    641: 
1.59      gdt       642: Note that loading the domU kernel from the dom0 implies that boot
                    643: blocks, /boot, /boot.cfg, and so on are all ignored in the domU.
1.48      gdt       644: See the VPS section near the end for discussion of alternate ways to
                    645: obtain domU kernels.
                    646: 
1.33      gdt       647: CPU and memory
                    648: --------------
                    649: 
1.48      gdt       650: A domain is provided with some number of vcpus, less than the number
                    651: of cpus seen by the hypervisor.  (For a dom0, this is controlled by
                    652: the boot argument "dom0_max_vcpus=1".)  For a domU, it is controlled
                    653: from the config file by the "vcpus = N" directive.
                    654: 
                    655: A domain is provided with memory; this is controlled in the config
                    656: file by "memory = N" (in megabytes).  In the straightforward case, the
                    657: sum of the the memory allocated to the dom0 and all domUs must be less
1.33      gdt       658: than the available memory.
                    659: 
                    660: Xen also provides a "balloon" driver, which can be used to let domains
                    661: use more memory temporarily.  TODO: Explain better, and explain how
                    662: well it works with NetBSD.
1.28      gdt       663: 
                    664: Virtual disks
                    665: -------------
                    666: 
1.33      gdt       667: With the file/vnd style, typically one creates a directory,
                    668: e.g. /u0/xen, on a disk large enough to hold virtual disks for all
                    669: domUs.  Then, for each domU disk, one writes zeros to a file that then
                    670: serves to hold the virtual disk's bits; a suggested name is foo-xbd0
                    671: for the first virtual disk for the domU called foo.  Writing zeros to
                    672: the file serves two purposes.  One is that preallocating the contents
                    673: improves performance.  The other is that vnd on sparse files has
                    674: failed to work.  TODO: give working/notworking NetBSD versions for
                    675: sparse vnd.  Note that the use of file/vnd for Xen is not really
                    676: different than creating a file-backed virtual disk for some other
1.39      gdt       677: purpose, except that xentools handles the vnconfig commands.  To
                    678: create an empty 4G virtual disk, simply do
                    679: 
                    680:         dd if=/dev/zero of=foo-xbd0 bs=1m count=4096
1.33      gdt       681: 
1.89      gdt       682: Do not use qemu-img-xen, because this will create sparse file.  There
                    683: have been recent (2015) reports of sparse vnd(4) devices causing
                    684: lockups, but there is apparently no PR.
                    685: 
1.33      gdt       686: With the lvm style, one creates logical devices.  They are then used
1.48      gdt       687: similarly to vnds.  TODO: Add an example with lvm.
                    688: 
                    689: In domU config files, the disks are defined as a sequence of 3-tuples.
                    690: The first element is "method:/path/to/disk".  Common methods are
                    691: "file:" for file-backed vnd. and "phy:" for something that is already
                    692: a (TODO: character or block) device.
                    693: 
                    694: The second element is an artifact of how virtual disks are passed to
                    695: Linux, and a source of confusion with NetBSD Xen usage.  Linux domUs
                    696: are given a device name to associate with the disk, and values like
                    697: "hda1" or "sda1" are common.  In a NetBSD domU, the first disk appears
                    698: as xbd0, the second as xbd1, and so on.  However, xm/xl demand a
                    699: second argument.  The name given is converted to a major/minor by
1.49      gdt       700: calling stat(2) on the name in /dev and this is passed to the domU.
                    701: In the general case, the dom0 and domU can be different operating
1.48      gdt       702: systems, and it is an unwarranted assumption that they have consistent
                    703: numbering in /dev, or even that the dom0 OS has a /dev.  With NetBSD
                    704: as both dom0 and domU, using values of 0x0 for the first disk and 0x1
1.49      gdt       705: for the second works fine and avoids this issue.  For a GNU/Linux
                    706: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for
                    707: /dev/hda1.
1.48      gdt       708: 
                    709: The third element is "w" for writable disks, and "r" for read-only
                    710: disks.
1.28      gdt       711: 
                    712: Virtual Networking
                    713: ------------------
                    714: 
1.46      gdt       715: Xen provides virtual ethernets, each of which connects the dom0 and a
                    716: domU.  For each virtual network, there is an interface "xvifN.M" in
                    717: the dom0, and in domU index N, a matching interface xennetM (NetBSD
                    718: name).  The interfaces behave as if there is an Ethernet with two
                    719: adaptors connected.  From this primitive, one can construct various
                    720: configurations.  We focus on two common and useful cases for which
                    721: there are existing scripts: bridging and NAT.
1.28      gdt       722: 
1.48      gdt       723: With bridging (in the example above), the domU perceives itself to be
                    724: on the same network as the dom0.  For server virtualization, this is
                    725: usually best.  Bridging is accomplished by creating a bridge(4) device
                    726: and adding the dom0's physical interface and the various xvifN.0
                    727: interfaces to the bridge.  One specifies "bridge=bridge0" in the domU
                    728: config file.  The bridge must be set up already in the dom0; an
                    729: example /etc/ifconfig.bridge0 is:
1.46      gdt       730: 
                    731:         create
                    732:         up
                    733:         !brconfig bridge0 add wm0
1.28      gdt       734: 
                    735: With NAT, the domU perceives itself to be behind a NAT running on the
                    736: dom0.  This is often appropriate when running Xen on a workstation.
1.48      gdt       737: TODO: NAT appears to be configured by "vif = [ '' ]".
1.28      gdt       738: 
1.49      gdt       739: The MAC address specified is the one used for the interface in the new
1.53      gdt       740: domain.  The interface in dom0 will use this address XOR'd with
1.49      gdt       741: 00:00:00:01:00:00.  Random MAC addresses are assigned if not given.
                    742: 
1.33      gdt       743: Sizing domains
                    744: --------------
                    745: 
                    746: Modern x86 hardware has vast amounts of resources.  However, many
                    747: virtual servers can function just fine on far less.  A system with
                    748: 256M of RAM and a 4G disk can be a reasonable choice.  Note that it is
                    749: far easier to adjust virtual resources than physical ones.  For
                    750: memory, it's just a config file edit and a reboot.  For disk, one can
                    751: create a new file and vnconfig it (or lvm), and then dump/restore,
                    752: just like updating physical disks, but without having to be there and
                    753: without those pesky connectors.
                    754: 
1.48      gdt       755: Starting domains automatically
                    756: ------------------------------
1.28      gdt       757: 
1.48      gdt       758: To start domains foo at bar at boot and shut them down cleanly on dom0
                    759: shutdown, in rc.conf add:
1.28      gdt       760: 
1.48      gdt       761:         xendomains="foo bar"
1.28      gdt       762: 
1.86      gdt       763: Note that earlier versions of the xentools41 xendomains rc.d scripth
                    764: usd xl, when one should use xm with 4.1.
1.28      gdt       765: 
                    766: Creating specific unprivileged domains (domU)
                    767: =============================================
1.14      gdt       768: 
                    769: Creating domUs is almost entirely independent of operating system.  We
1.49      gdt       770: have already presented the basics of config files.  Note that you must
                    771: have already completed the dom0 setup so that "xl list" (or "xm list")
                    772: works.
1.14      gdt       773: 
                    774: Creating an unprivileged NetBSD domain (domU)
                    775: ---------------------------------------------
1.1       mspo      776: 
1.49      gdt       777: See the earlier config file, and adjust memory.  Decide on how much
                    778: storage you will provide, and prepare it (file or lvm).
                    779: 
                    780: While the kernel will be obtained from the dom0 filesystem, the same
                    781: file should be present in the domU as /netbsd so that tools like
                    782: savecore(8) can work.   (This is helpful but not necessary.)
                    783: 
                    784: The kernel must be specifically for Xen and for use as a domU.  The
                    785: i386 and amd64 provide the following kernels:
                    786: 
                    787:         i386 XEN3_DOMU
                    788:         i386 XEN3PAE_DOMU
1.95      gdt       789:         amd64 XEN3_DOMU
1.5       mspo      790: 
1.49      gdt       791: Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must
                    792: use the PAE version of the i386 kernel.
                    793: 
                    794: This will boot NetBSD, but this is not that useful if the disk is
                    795: empty.  One approach is to unpack sets onto the disk outside of xen
                    796: (by mounting it, just as you would prepare a physical disk for a
                    797: system you can't run the installer on).
                    798: 
                    799: A second approach is to run an INSTALL kernel, which has a miniroot
                    800: and can load sets from the network.  To do this, copy the INSTALL
                    801: kernel to / and change the kernel line in the config file to:
1.5       mspo      802: 
1.49      gdt       803:         kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU"
1.5       mspo      804: 
1.49      gdt       805: Then, start the domain as "xl create -c configname".
1.1       mspo      806: 
1.49      gdt       807: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following
                    808: line should be used in the config file.
1.1       mspo      809: 
1.3       mspo      810:     disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ]
1.1       mspo      811: 
                    812: After booting the domain, the option to install via CDROM may be
1.49      gdt       813: selected.  The CDROM device should be changed to `xbd1d`.
1.1       mspo      814: 
1.49      gdt       815: Once done installing, "halt -p" the new domain (don't reboot or halt,
                    816: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the
                    817: config file), switch the config file back to the XEN3_DOMU kernel,
                    818: and start the new domain again. Now it should be able to use "root on
                    819: xbd0a" and you should have a, functional NetBSD domU.
1.1       mspo      820: 
1.49      gdt       821: TODO: check if this is still accurate.
1.1       mspo      822: When the new domain is booting you'll see some warnings about *wscons*
                    823: and the pseudo-terminals. These can be fixed by editing the files
1.5       mspo      824: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in
                    825: `/etc/ttys`, except *console*, like this:
1.1       mspo      826: 
1.3       mspo      827:     console "/usr/libexec/getty Pc"         vt100   on secure
                    828:     ttyE0   "/usr/libexec/getty Pc"         vt220   off secure
                    829:     ttyE1   "/usr/libexec/getty Pc"         vt220   off secure
                    830:     ttyE2   "/usr/libexec/getty Pc"         vt220   off secure
                    831:     ttyE3   "/usr/libexec/getty Pc"         vt220   off secure
1.1       mspo      832: 
1.5       mspo      833: Finally, all screens must be commented out from `/etc/wscons.conf`.
1.1       mspo      834: 
                    835: It is also desirable to add
                    836: 
1.49      gdt       837:         powerd=YES
1.1       mspo      838: 
1.5       mspo      839: in rc.conf. This way, the domain will be properly shut down if
1.53      gdt       840: `xm shutdown -R` or `xm shutdown -H` is used on the dom0.
1.1       mspo      841: 
1.92      gdt       842: It is not strictly necessary to have a kernel (as /netbsd) in the domU
                    843: filesystem.  However, various programs (e.g. netstat) will use that
                    844: kernel to look up symbols to read from kernel virtual memory.  If
                    845: /netbsd is not the running kernel, those lookups will fail.  (This is
                    846: not really a Xen-specific issue, but because the domU kernel is
                    847: obtained from the dom0, it is far more likely to be out of sync or
                    848: missing with Xen.)
                    849: 
1.14      gdt       850: Creating an unprivileged Linux domain (domU)
1.5       mspo      851: --------------------------------------------
1.1       mspo      852: 
                    853: Creating unprivileged Linux domains isn't much different from
                    854: unprivileged NetBSD domains, but there are some details to know.
                    855: 
                    856: First, the second parameter passed to the disk declaration (the '0x1' in
                    857: the example below)
                    858: 
1.3       mspo      859:     disk = [ 'phy:/dev/wd0e,0x1,w' ]
1.1       mspo      860: 
                    861: does matter to Linux. It wants a Linux device number here (e.g. 0x300
1.49      gdt       862: for hda).  Linux builds device numbers as: (major \<\< 8 + minor).
                    863: So, hda1 which has major 3 and minor 1 on a Linux system will have
                    864: device number 0x301.  Alternatively, devices names can be used (hda,
                    865: hdb, ...)  as xentools has a table to map these names to devices
                    866: numbers.  To export a partition to a Linux guest we can use:
1.1       mspo      867: 
1.49      gdt       868:         disk = [ 'phy:/dev/wd0e,0x300,w' ]
                    869:         root = "/dev/hda1 ro"
1.1       mspo      870: 
                    871: and it will appear as /dev/hda on the Linux system, and be used as root
                    872: partition.
                    873: 
1.49      gdt       874: To install the Linux system on the partition to be exported to the
                    875: guest domain, the following method can be used: install
                    876: sysutils/e2fsprogs from pkgsrc.  Use mke2fs to format the partition
                    877: that will be the root partition of your Linux domain, and mount it.
                    878: Then copy the files from a working Linux system, make adjustments in
                    879: `/etc` (fstab, network config).  It should also be possible to extract
                    880: binary packages such as .rpm or .deb directly to the mounted partition
                    881: using the appropriate tool, possibly running under NetBSD's Linux
                    882: emulation.  Once the filesystem has been populated, umount it.  If
                    883: desirable, the filesystem can be converted to ext3 using tune2fs -j.
                    884: It should now be possible to boot the Linux guest domain, using one of
                    885: the vmlinuz-\*-xenU kernels available in the Xen binary distribution.
1.1       mspo      886: 
                    887: To get the linux console right, you need to add:
                    888: 
1.3       mspo      889:     extra = "xencons=tty1"
1.1       mspo      890: 
                    891: to your configuration since not all linux distributions auto-attach a
                    892: tty to the xen console.
                    893: 
1.14      gdt       894: Creating an unprivileged Solaris domain (domU)
1.5       mspo      895: ----------------------------------------------
1.1       mspo      896: 
1.50      gdt       897: See possibly outdated
                    898: [Solaris domU instructions](/ports/xen/howto-solaris/).
1.5       mspo      899: 
1.1       mspo      900: 
1.52      gdt       901: PCI passthrough: Using PCI devices in guest domains
                    902: ---------------------------------------------------
1.1       mspo      903: 
1.53      gdt       904: The dom0 can give other domains access to selected PCI
1.52      gdt       905: devices. This can allow, for example, a non-privileged domain to have
                    906: access to a physical network interface or disk controller.  However,
                    907: keep in mind that giving a domain access to a PCI device most likely
                    908: will give the domain read/write access to the whole physical memory,
                    909: as PCs don't have an IOMMU to restrict memory access to DMA-capable
1.53      gdt       910: device.  Also, it's not possible to export ISA devices to non-dom0
1.52      gdt       911: domains, which means that the primary VGA adapter can't be exported.
                    912: A guest domain trying to access the VGA registers will panic.
                    913: 
1.53      gdt       914: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has
1.52      gdt       915: not been ported to later versions at this time.
                    916: 
                    917: For a PCI device to be exported to a domU, is has to be attached to
                    918: the "pciback" driver in dom0.  Devices passed to the dom0 via the
                    919: pciback.hide boot parameter will attach to "pciback" instead of the
                    920: usual driver.  The list of devices is specified as "(bus:dev.func)",
1.5       mspo      921: where bus and dev are 2-digit hexadecimal numbers, and func a
                    922: single-digit number:
1.1       mspo      923: 
1.52      gdt       924:         pciback.hide=(00:0a.0)(00:06.0)
1.1       mspo      925: 
1.52      gdt       926: pciback devices should show up in the dom0's boot messages, and the
1.5       mspo      927: devices should be listed in the `/kern/xen/pci` directory.
1.1       mspo      928: 
1.52      gdt       929: PCI devices to be exported to a domU are listed in the "pci" array of
                    930: the domU's config file, with the format "0000:bus:dev.func".
1.1       mspo      931: 
1.52      gdt       932:         pci = [ '0000:00:06.0', '0000:00:0a.0' ]
1.1       mspo      933: 
1.52      gdt       934: In the domU an "xpci" device will show up, to which one or more pci
                    935: busses will attach.  Then the PCI drivers will attach to PCI busses as
                    936: usual.  Note that the default NetBSD DOMU kernels do not have "xpci"
                    937: or any PCI drivers built in by default; you have to build your own
                    938: kernel to use PCI devices in a domU.  Here's a kernel config example;
                    939: note that only the "xpci" lines are unusual.
                    940: 
                    941:         include         "arch/i386/conf/XEN3_DOMU"
                    942: 
                    943:         # Add support for PCI busses to the XEN3_DOMU kernel
                    944:         xpci* at xenbus ?
                    945:         pci* at xpci ?
                    946: 
                    947:         # PCI USB controllers
                    948:         uhci*   at pci? dev ? function ?        # Universal Host Controller (Intel)
                    949: 
                    950:         # USB bus support
                    951:         usb*    at uhci?
                    952: 
                    953:         # USB Hubs
                    954:         uhub*   at usb?
                    955:         uhub*   at uhub? port ? configuration ? interface ?
                    956: 
                    957:         # USB Mass Storage
                    958:         umass*  at uhub? port ? configuration ? interface ?
                    959:         wd*     at umass?
                    960:         # SCSI controllers
                    961:         ahc*    at pci? dev ? function ?        # Adaptec [23]94x, aic78x0 SCSI
                    962: 
                    963:         # SCSI bus support (for both ahc and umass)
                    964:         scsibus* at scsi?
                    965: 
                    966:         # SCSI devices
                    967:         sd*     at scsibus? target ? lun ?      # SCSI disk drives
                    968:         cd*     at scsibus? target ? lun ?      # SCSI CD-ROM drives
1.1       mspo      969: 
                    970: 
1.28      gdt       971: NetBSD as a domU in a VPS
                    972: =========================
                    973: 
                    974: The bulk of the HOWTO is about using NetBSD as a dom0 on your own
                    975: hardware.  This section explains how to deal with Xen in a domU as a
                    976: virtual private server where you do not control or have access to the
1.70      gdt       977: dom0.  This is not intended to be an exhaustive list of VPS providers;
                    978: only a few are mentioned that specifically support NetBSD.
1.28      gdt       979: 
1.52      gdt       980: VPS operators provide varying degrees of access and mechanisms for
                    981: configuration.  The big issue is usually how one controls which kernel
                    982: is booted, because the kernel is nominally in the dom0 filesystem (to
1.70      gdt       983: which VPS users do not normally have acesss).  A second issue is how
                    984: to install NetBSD.
1.52      gdt       985: A VPS user may want to compile a kernel for security updates, to run
                    986: npf, run IPsec, or any other reason why someone would want to change
                    987: their kernel.
                    988: 
                    989: One approach is to have an adminstrative interface to upload a kernel,
1.68      gdt       990: or to select from a prepopulated list.  Other approaches are pygrub
1.59      gdt       991: (deprecated) and pvgrub, which are ways to have a bootloader obtain a
                    992: kernel from the domU filesystem.  This is closer to a regular physical
                    993: computer, where someone who controls a machine can replace the kernel.
1.52      gdt       994: 
1.74      gdt       995: A second issue is multiple CPUs.  With NetBSD 6, domUs support
                    996: multiple vcpus, and it is typical for VPS providers to enable multiple
                    997: CPUs for NetBSD domUs.
                    998: 
1.68      gdt       999: pygrub
1.59      gdt      1000: -------
1.52      gdt      1001: 
1.68      gdt      1002: pygrub runs in the dom0 and looks into the domU filesystem.  This
1.59      gdt      1003: implies that the domU must have a kernel in a filesystem in a format
1.68      gdt      1004: known to pygrub.  As of 2014, pygrub seems to be of mostly historical
                   1005: interest.
1.52      gdt      1006: 
1.59      gdt      1007: pvgrub
                   1008: ------
                   1009: 
                   1010: pvgrub is a version of grub that uses PV operations instead of BIOS
                   1011: calls.  It is booted from the dom0 as the domU kernel, and then reads
                   1012: /grub/menu.lst and loads a kernel from the domU filesystem.
                   1013: 
1.70      gdt      1014: [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports
1.71      gdt      1015: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes
                   1016: (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub
1.70      gdt      1017: page](http://www.panix.com/v-colo/grub.html), which describes only
1.74      gdt      1018: Linux but should be updated to cover NetBSD :-).
1.70      gdt      1019: 
                   1020: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot
                   1021: their own kernel.  See then [prgmr.com NetBSD
1.74      gdt      1022: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
                   1023: (which is in need of updating).
1.59      gdt      1024: 
1.70      gdt      1025: It appears that [grub's FFS
                   1026: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
                   1027: does not support all aspects of modern FFS, but there are also reports
1.72      gdt      1028: that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT
1.70      gdt      1029: partition for the kernel with the intent that grub can understand it,
                   1030: which leads to /netbsd not being the actual kernel.  One must remember
                   1031: to update the special boot partiion.
1.59      gdt      1032: 
                   1033: Amazon
                   1034: ------
                   1035: 
1.95      gdt      1036: See the [Amazon EC2 page](../amazon_ec2/).
1.44      gdt      1037: 
                   1038: Using npf
                   1039: ---------
                   1040: 
1.81      gdt      1041: In standard kernels, npf is a module, and thus cannot be loaded in a
1.44      gdt      1042: DOMU kernel.
                   1043: 
1.95      gdt      1044: TODO: Explain how to compile npf into a custom kernel, answering (but
                   1045: note that the problem was caused by not booting the right kernel)
                   1046: [this email to
                   1047: netbsd-users](http://mail-index.netbsd.org/netbsd-users/2014/12/26/msg015576.html).
1.65      gdt      1048: 
                   1049: TODO items for improving NetBSD/xen
                   1050: ===================================
                   1051: 
1.93      gdt      1052: * Make the NetBSD dom0 kernel work with SMP.
                   1053: * Test the Xen 4.5 packages adequately to be able to recommend them as
                   1054:   the standard approach.
                   1055: * Get PCI passthrough working on Xen 4.5
1.65      gdt      1056: * Get pvgrub into pkgsrc, either via xentools or separately.
                   1057: * grub
1.70      gdt      1058:   * Check/add support to pkgsrc grub2 for UFS2 and arbitrary
1.66      gdt      1059:     fragsize/blocksize (UFS2 support may be present; the point is to
                   1060:     make it so that with any UFS1/UFS2 filesystem setup that works
                   1061:     with NetBSD grub will also work).
1.70      gdt      1062:     See [pkg/40258](http://gnats.netbsd.org/40258).
1.65      gdt      1063:   * Push patches upstream.
                   1064:   * Get UFS2 patches into pvgrub.
                   1065: * Add support for PV ops to a version of /boot, and make it usable as
                   1066:   a kernel in Xen, similar to pvgrub.
1.93      gdt      1067: * Solve somehow the issue with modules for GENERIC not being loadable
                   1068:   in a Xen dom0 or domU kernel.
                   1069: 
                   1070: Random pointers
                   1071: ===============
                   1072: 
                   1073: TODO: This section contains links from elsewhere not yet integrated
                   1074: into the HOWTO.
                   1075: 
                   1076: * http://www.lumbercartel.ca/library/xen/
                   1077: * http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html

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