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Sun Nov 15 14:11:07 2020 UTC (2 months ago) by gdt
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Explain PVHv1

1: [[!meta title="Xen HowTo"]] 2: 3: Xen is a Type 1 hypervisor which supports running multiple guest operating 4: systems on a single physical machine. One uses the Xen kernel to control the 5: CPU, memory and console, a dom0 operating system which mediates access to 6: other hardware (e.g., disks, network, USB), and one or more domU operating 7: systems which operate in an unprivileged virtualized environment. IO requests 8: from the domU systems are forwarded by the Xen hypervisor to the dom0 to be 9: fulfilled. 10: 11: Xen supports different styles of guests; see [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM) and [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu) for upstream documentation. 12: 13: [[!table data=""" 14: Style of guest |Supported by NetBSD 15: PV |Yes (dom0, domU) 16: HVM |Yes (domU) 17: PVHVM |current-only (domU) 18: PVHv2 |current-only (domU, dom0 not yet) 19: """]] 20: 21: In Para-Virtualized (PV) mode, the guest OS does not attempt to access 22: hardware directly, but instead makes hypercalls to the hypervisor; PV 23: guests must be specifically coded for Xen. 24: 25: In HVM mode, no guest modification is required; however, hardware 26: support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs. 27: The dom0 runs qemu to emulate hardware. 28: 29: In PVHVM mode, the guest runs as HVM, but additionally can use PV 30: drivers for efficiency. 31: 32: In PVHv2 mode, operation is similar to PVHVM, except that qemu is not 33: run and thus the PV interfaces for console, disks, networking are the 34: only way to access these resources. (There was an original PVH mode 35: that is no longer in use, and now, sometimes PVHv2 is referred to as 36: simply PVH.) 37: 38: At boot, the dom0 kernel is loaded as a module with Xen as the kernel. 39: The dom0 can start one or more domUs. (Booting is explained in detail 40: in the dom0 section.) 41: 42: This HOWTO presumes a basic familiarity with the Xen system 43: architecture, with installing NetBSD on i386/amd64 hardware, and with 44: installing software from pkgsrc. See also the [Xen 45: website](http://www.xenproject.org/). 46: 47: [[!toc]] 48: 49: # Versions and Support 50: 51: In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages 52: xenkernel and xentools. We will refer only to the kernel versions, 53: but note that both packages must be installed together and must have 54: matching versions. 55: 56: Versions available in pkgsrc: 57: 58: [[!table data=""" 59: Xen Version |Package Name |Xen CPU Support |xm? |EOL'ed By Upstream 60: 4.11 |xenkernel411 |x86_64 | |No 61: 4.13 |xenkernel413 |x86_64 | |No 62: """]] 63: 64: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/). 65: 66: Multiprocessor (SMP) support in NetBSD differs depending on the domain: 67: 68: [[!table data=""" 69: Domain |Supports SMP 70: dom0 |No 71: domU |Yes 72: """]] 73: 74: Note: NetBSD support is called XEN3. However, it does support Xen 4, 75: because the hypercall interface has remained identical. 76: 77: Older Xen had a python-based management tool called xm, now replaced 78: by xl. 79: 80: Architecture 81: ------------ 82: 83: Xen 4.5 and later runs on x86_64 hardware (the NetBSD amd64 port). 84: There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD. 85: 86: The dom0 system should be amd64. (Instructions for i386PAE dom0 have been removed from the HOWTO.) 87: 88: The domU can be i386PAE or amd64. 89: i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64. 90: 91: # Creating a dom0 92: 93: In order to install a NetBSD as a dom0, one must first install a normal 94: NetBSD system, and then pivot the install to a dom0 install by changing 95: the kernel and boot configuration. 96: 97: In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with 98: 512M it worked reliably. This does not make sense, but if you see 99: "not ELF" after Xen boots, try increasing dom0 RAM. 100: 101: Installation of NetBSD 102: ---------------------- 103: 104: [Install NetBSD/amd64](/guide/inst/) 105: just as you would if you were not using Xen. 106: 107: Installation of Xen 108: ------------------- 109: 110: We will consider that you chose to use Xen 4.13, with NetBSD/amd64 as 111: dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc. 112: 113: Once this is done, install the Xen kernel itself: 114: 115: [[!template id=programlisting text=""" 116: # cp /usr/pkg/xen48-kernel/xen.gz / 117: """]] 118: 119: Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such kernel 120: can either be compiled manually, or downloaded from the NetBSD FTP, for 121: example at: 122: 123: [[!template id=programlisting text=""" 124: ftp.netbsd.org/pub/NetBSD/NetBSD-8.0/amd64/binary/kernel/netbsd-XEN3_DOM0.gz 125: """]] 126: 127: Add a line to /boot.cfg to boot Xen: 128: 129: [[!template id=filecontent name="/boot.cfg" text=""" 130: menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M 131: """]] 132: 133: This specifies that the dom0 should have 512MB of ram, leaving the rest 134: to be allocated for domUs. To use a serial console, use: 135: 136: [[!template id=filecontent name="/boot.cfg" text=""" 137: menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1 138: """]] 139: 140: which will use the first serial port for Xen (which counts starting 141: from 1, unlike NetBSD which counts starting from 0), forcing 142: speed/parity. Because the NetBSD command line lacks a 143: "console=pc" argument, it will use the default "xencons" console device, 144: which directs the console I/O through Xen to the same console device Xen 145: itself uses (in this case, the serial port). 146: 147: In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`, 148: to force only one vcpu to be provided (since NetBSD dom0 can't use 149: more) and to pin that vcpu to a physical CPU. Xen has 150: [many boot options](http://xenbits.xenproject.org/docs/4.13-testing/misc/xen-command-line.html), 151: and other than dom0 memory and max_vcpus, they are generally not 152: necessary. 153: 154: Copy the boot scripts into `/etc/rc.d`: 155: 156: [[!template id=programlisting text=""" 157: # cp /usr/pkg/share/examples/rc.d/xen* /etc/rc.d/ 158: """]] 159: 160: Enable `xencommons`: 161: 162: [[!template id=filecontent name="/etc/rc.conf" text=""" 163: xencommons=YES 164: """]] 165: 166: Now, reboot so that you are running a DOM0 kernel under Xen, rather 167: than GENERIC without Xen. 168: 169: TODO: Recommend for/against xen-watchdog. 170: 171: Once the reboot is done, use `xl` to inspect Xen's boot messages, 172: available resources, and running domains. For example: 173: 174: [[!template id=programlisting text=""" 175: # xl dmesg 176: ... xen's boot info ... 177: # xl info 178: ... available memory, etc ... 179: # xl list 180: Name Id Mem(MB) CPU State Time(s) Console 181: Domain-0 0 64 0 r---- 58.1 182: """]] 183: 184: Xen logs will be in /var/log/xen. 185: 186: ### Issues with xencommons 187: 188: `xencommons` starts `xenstored`, which stores data on behalf of dom0 and 189: domUs. It does not currently work to stop and start xenstored. 190: Certainly all domUs should be shutdown first, following the sort order 191: of the rc.d scripts. However, the dom0 sets up state with xenstored, 192: and is not notified when xenstored exits, leading to not recreating 193: the state when the new xenstored starts. Until there's a mechanism to 194: make this work, one should not expect to be able to restart xenstored 195: (and thus xencommons). There is currently no reason to expect that 196: this will get fixed any time soon. 197: 198: anita (for testing NetBSD) 199: -------------------------- 200: 201: With the setup so far, one should be able to run 202: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as 203: root, because anita must create a domU): 204: 205: [[!template id=programlisting text=""" 206: anita --vmm=xl test file:///usr/obj/i386/ 207: """]] 208: 209: Xen-specific NetBSD issues 210: -------------------------- 211: 212: There are (at least) two additional things different about NetBSD as a 213: dom0 kernel compared to hardware. 214: 215: One is that the module ABI is different because some of the #defines 216: change, so one must build modules for Xen. As of netbsd-7, the build 217: system does this automatically. 218: 219: The other difference is that XEN3_DOM0 does not have exactly the same 220: options as GENERIC. While it is debatable whether or not this is a 221: bug, users should be aware of this and can simply add missing config 222: items if desired. 223: 224: Updating NetBSD in a dom0 225: ------------------------- 226: 227: This is just like updating NetBSD on bare hardware, assuming the new 228: version supports the version of Xen you are running. Generally, one 229: replaces the kernel and reboots, and then overlays userland binaries 230: and adjusts `/etc`. 231: 232: Note that one must update both the non-Xen kernel typically used for 233: rescue purposes and the DOM0 kernel used with Xen. 234: 235: Converting from grub to /boot 236: ----------------------------- 237: 238: These instructions were used to convert a system from 239: grub to /boot. The system was originally installed in February of 240: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated 241: over time. Before these commands, it was running NetBSD 6 i386, Xen 242: 4.1 and grub, much like the message linked earlier in the grub 243: section. 244: 245: [[!template id=programlisting text=""" 246: # Install MBR bootblocks on both disks. 247: fdisk -i /dev/rwd0d 248: fdisk -i /dev/rwd1d 249: # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components. 250: installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1 251: installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1 252: # Install secondary boot loader 253: cp -p /usr/mdec/boot / 254: # Create boot.cfg following earlier guidance: 255: menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M 256: menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M 257: menu=GENERIC:boot 258: menu=GENERIC single-user:boot -s 259: menu=GENERIC.ok:boot netbsd.ok 260: menu=GENERIC.ok single-user:boot netbsd.ok -s 261: menu=Drop to boot prompt:prompt 262: default=1 263: timeout=30 264: """]] 265: 266: Upgrading Xen versions 267: --------------------- 268: 269: Minor version upgrades are trivial. Just rebuild/replace the 270: xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg` 271: references it), and reboot. 272: 273: #Unprivileged domains (domU) 274: 275: This section describes general concepts about domUs. It does not 276: address specific domU operating systems or how to install them. The 277: config files for domUs are typically in `/usr/pkg/etc/xen`, and are 278: typically named so that the file name, domU name and the domU's host 279: name match. 280: 281: The domU is provided with CPU and memory by Xen, configured by the 282: dom0. The domU is provided with disk and network by the dom0, 283: mediated by Xen, and configured in the dom0. 284: 285: Entropy in domUs can be an issue; physical disks and network are on 286: the dom0. NetBSD's /dev/random system works, but is often challenged. 287: 288: Config files 289: ------------ 290: 291: See /usr/pkg/share/examples/xen/xlexample* 292: for a small number of well-commented examples, mostly for running 293: GNU/Linux. 294: 295: The following is an example minimal domain configuration file. The domU 296: serves as a network file server. 297: 298: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text=""" 299: name = "domU-id" 300: kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz" 301: memory = 1024 302: vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ] 303: disk = [ 'file:/n0/xen/foo-wd0,0x0,w', 304: 'file:/n0/xen/foo-wd1,0x1,w' ] 305: """]] 306: 307: The domain will have name given in the `name` setting. The kernel has the 308: host/domU name in it, so that on the dom0 one can update the various 309: domUs independently. The `vif` line causes an interface to be provided, 310: with a specific mac address (do not reuse MAC addresses!), in bridge 311: mode. Two disks are provided, and they are both writable; the bits 312: are stored in files and Xen attaches them to a vnd(4) device in the 313: dom0 on domain creation. The system treats xbd0 as the boot device 314: without needing explicit configuration. 315: 316: By convention, domain config files are kept in `/usr/pkg/etc/xen`. Note 317: that "xl create" takes the name of a config file, while other commands 318: take the name of a domain. 319: 320: Examples of commands: 321: 322: [[!template id=programlisting text=""" 323: xl create /usr/pkg/etc/xen/foo 324: xl console domU-id 325: xl create -c /usr/pkg/etc/xen/foo 326: xl shutdown domU-id 327: xl list 328: """]] 329: 330: Typing `^]` will exit the console session. Shutting down a domain is 331: equivalent to pushing the power button; a NetBSD domU will receive a 332: power-press event and do a clean shutdown. Shutting down the dom0 333: will trigger controlled shutdowns of all configured domUs. 334: 335: CPU and memory 336: -------------- 337: 338: A domain is provided with some number of vcpus, up to the number 339: of CPUs seen by the hypervisor. For a domU, it is controlled 340: from the config file by the "vcpus = N" directive. 341: 342: A domain is provided with memory; this is controlled in the config 343: file by "memory = N" (in megabytes). In the straightforward case, the 344: sum of the the memory allocated to the dom0 and all domUs must be less 345: than the available memory. 346: 347: Xen also provides a "balloon" driver, which can be used to let domains 348: use more memory temporarily. 349: 350: Virtual disks 351: ------------- 352: 353: In domU config files, the disks are defined as a sequence of 3-tuples: 354: 355: * The first element is "method:/path/to/disk". Common methods are 356: "file:" for a file-backed vnd, and "phy:" for something that is already 357: a device, such as an LVM logical volume. 358: 359: * The second element is an artifact of how virtual disks are passed to 360: Linux, and a source of confusion with NetBSD Xen usage. Linux domUs 361: are given a device name to associate with the disk, and values like 362: "hda1" or "sda1" are common. In a NetBSD domU, the first disk appears 363: as xbd0, the second as xbd1, and so on. However, xl demands a 364: second argument. The name given is converted to a major/minor by 365: calling stat(2) on the name in /dev and this is passed to the domU. 366: In the general case, the dom0 and domU can be different operating 367: systems, and it is an unwarranted assumption that they have consistent 368: numbering in /dev, or even that the dom0 OS has a /dev. With NetBSD 369: as both dom0 and domU, using values of 0x0 for the first disk and 0x1 370: for the second works fine and avoids this issue. For a GNU/Linux 371: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for 372: /dev/hda1. 373: 374: * The third element is "w" for writable disks, and "r" for read-only 375: disks. 376: 377: Example: 378: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text=""" 379: disk = [ 'file:/n0/xen/foo-wd0,0x0,w' ] 380: """]] 381: 382: Note that NetBSD by default creates only vnd[0123]. If you need more 383: than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the 384: dom0. 385: 386: Note that NetBSD by default creates only xbd[0123]. If you need more 387: virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU. 388: 389: Virtual Networking 390: ------------------ 391: 392: Xen provides virtual Ethernets, each of which connects the dom0 and a 393: domU. For each virtual network, there is an interface "xvifN.M" in 394: the dom0, and a matching interface xennetM (NetBSD name) in domU index N. 395: The interfaces behave as if there is an Ethernet with two 396: adapters connected. From this primitive, one can construct various 397: configurations. We focus on two common and useful cases for which 398: there are existing scripts: bridging and NAT. 399: 400: With bridging (in the example above), the domU perceives itself to be 401: on the same network as the dom0. For server virtualization, this is 402: usually best. Bridging is accomplished by creating a bridge(4) device 403: and adding the dom0's physical interface and the various xvifN.0 404: interfaces to the bridge. One specifies "bridge=bridge0" in the domU 405: config file. The bridge must be set up already in the dom0; an 406: example /etc/ifconfig.bridge0 is: 407: 408: [[!template id=filecontent name="/etc/ifconfig.bridge0" text=""" 409: create 410: up 411: !brconfig bridge0 add wm0 412: """]] 413: 414: With NAT, the domU perceives itself to be behind a NAT running on the 415: dom0. This is often appropriate when running Xen on a workstation. 416: TODO: NAT appears to be configured by "vif = [ '' ]". 417: 418: The MAC address specified is the one used for the interface in the new 419: domain. The interface in dom0 will use this address XOR'd with 420: 00:00:00:01:00:00. Random MAC addresses are assigned if not given. 421: 422: Starting domains automatically 423: ------------------------------ 424: 425: To start domains `domU-netbsd` and `domU-linux` at boot and shut them 426: down cleanly on dom0 shutdown, add the following in rc.conf: 427: 428: [[!template id=filecontent name="/etc/rc.conf" text=""" 429: xendomains="domU-netbsd domU-linux" 430: """]] 431: 432: #Creating a domU 433: 434: Creating domUs is almost entirely independent of operating system. We 435: have already presented the basics of config files. Note that you must 436: have already completed the dom0 setup so that "xl list" works. 437: 438: Creating a NetBSD domU 439: ---------------------- 440: 441: See the earlier config file, and adjust memory. Decide on how much 442: storage you will provide, and prepare it (file or LVM). 443: 444: While the kernel will be obtained from the dom0 file system, the same 445: file should be present in the domU as /netbsd so that tools like 446: savecore(8) can work. (This is helpful but not necessary.) 447: 448: The kernel must be specifically for Xen and for use as a domU. The 449: i386 and amd64 provide the following kernels: 450: 451: i386 XEN3PAE_DOMU 452: amd64 XEN3_DOMU 453: 454: This will boot NetBSD, but this is not that useful if the disk is 455: empty. One approach is to unpack sets onto the disk outside of xen 456: (by mounting it, just as you would prepare a physical disk for a 457: system you can't run the installer on). 458: 459: A second approach is to run an INSTALL kernel, which has a miniroot 460: and can load sets from the network. To do this, copy the INSTALL 461: kernel to / and change the kernel line in the config file to: 462: 463: kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU" 464: 465: Then, start the domain as "xl create -c configfile". 466: 467: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following 468: line should be used in the config file. 469: 470: disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ] 471: 472: After booting the domain, the option to install via CDROM may be 473: selected. The CDROM device should be changed to `xbd1d`. 474: 475: Once done installing, "halt -p" the new domain (don't reboot or halt, 476: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the 477: config file), switch the config file back to the XEN3_DOMU kernel, 478: and start the new domain again. Now it should be able to use "root on 479: xbd0a" and you should have a, functional NetBSD domU. 480: 481: TODO: check if this is still accurate. 482: When the new domain is booting you'll see some warnings about *wscons* 483: and the pseudo-terminals. These can be fixed by editing the files 484: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in 485: `/etc/ttys`, except *console*, like this: 486: 487: console "/usr/libexec/getty Pc" vt100 on secure 488: ttyE0 "/usr/libexec/getty Pc" vt220 off secure 489: ttyE1 "/usr/libexec/getty Pc" vt220 off secure 490: ttyE2 "/usr/libexec/getty Pc" vt220 off secure 491: ttyE3 "/usr/libexec/getty Pc" vt220 off secure 492: 493: Finally, all screens must be commented out from `/etc/wscons.conf`. 494: 495: It is also desirable to add 496: 497: powerd=YES 498: 499: in rc.conf. This way, the domain will be properly shut down if 500: `xm shutdown -R` or `xm shutdown -H` is used on the dom0. 501: 502: It is not strictly necessary to have a kernel (as /netbsd) in the domU 503: file system. However, various programs (e.g. netstat) will use that 504: kernel to look up symbols to read from kernel virtual memory. If 505: /netbsd is not the running kernel, those lookups will fail. (This is 506: not really a Xen-specific issue, but because the domU kernel is 507: obtained from the dom0, it is far more likely to be out of sync or 508: missing with Xen.) 509: 510: Creating a Linux domU 511: --------------------- 512: 513: Creating unprivileged Linux domains isn't much different from 514: unprivileged NetBSD domains, but there are some details to know. 515: 516: First, the second parameter passed to the disk declaration (the '0x1' in 517: the example below) 518: 519: disk = [ 'phy:/dev/wd0e,0x1,w' ] 520: 521: does matter to Linux. It wants a Linux device number here (e.g. 0x300 522: for hda). Linux builds device numbers as: (major \<\< 8 + minor). 523: So, hda1 which has major 3 and minor 1 on a Linux system will have 524: device number 0x301. Alternatively, devices names can be used (hda, 525: hdb, ...) as xentools has a table to map these names to devices 526: numbers. To export a partition to a Linux guest we can use: 527: 528: disk = [ 'phy:/dev/wd0e,0x300,w' ] 529: root = "/dev/hda1 ro" 530: 531: and it will appear as /dev/hda on the Linux system, and be used as root 532: partition. 533: 534: To install the Linux system on the partition to be exported to the 535: guest domain, the following method can be used: install 536: sysutils/e2fsprogs from pkgsrc. Use mke2fs to format the partition 537: that will be the root partition of your Linux domain, and mount it. 538: Then copy the files from a working Linux system, make adjustments in 539: `/etc` (fstab, network config). It should also be possible to extract 540: binary packages such as .rpm or .deb directly to the mounted partition 541: using the appropriate tool, possibly running under NetBSD's Linux 542: emulation. Once the file system has been populated, umount it. If 543: desirable, the file system can be converted to ext3 using tune2fs -j. 544: It should now be possible to boot the Linux guest domain, using one of 545: the vmlinuz-\*-xenU kernels available in the Xen binary distribution. 546: 547: To get the Linux console right, you need to add: 548: 549: extra = "xencons=tty1" 550: 551: to your configuration since not all Linux distributions auto-attach a 552: tty to the xen console. 553: 554: Creating a Solaris domU 555: ----------------------- 556: 557: See possibly outdated 558: [Solaris domU instructions](/ports/xen/howto-solaris/). 559: 560: 561: PCI passthrough: Using PCI devices in guest domains 562: --------------------------------------------------- 563: 564: The dom0 can give other domains access to selected PCI 565: devices. This can allow, for example, a non-privileged domain to have 566: access to a physical network interface or disk controller. However, 567: keep in mind that giving a domain access to a PCI device most likely 568: will give the domain read/write access to the whole physical memory, 569: as PCs don't have an IOMMU to restrict memory access to DMA-capable 570: device. Also, it's not possible to export ISA devices to non-dom0 571: domains, which means that the primary VGA adapter can't be exported. 572: A guest domain trying to access the VGA registers will panic. 573: 574: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has 575: not been ported to later versions at this time. 576: 577: For a PCI device to be exported to a domU, is has to be attached to 578: the "pciback" driver in dom0. Devices passed to the dom0 via the 579: pciback.hide boot parameter will attach to "pciback" instead of the 580: usual driver. The list of devices is specified as "(bus:dev.func)", 581: where bus and dev are 2-digit hexadecimal numbers, and func a 582: single-digit number: 583: 584: pciback.hide=(00:0a.0)(00:06.0) 585: 586: pciback devices should show up in the dom0's boot messages, and the 587: devices should be listed in the `/kern/xen/pci` directory. 588: 589: PCI devices to be exported to a domU are listed in the "pci" array of 590: the domU's config file, with the format "0000:bus:dev.func". 591: 592: pci = [ '0000:00:06.0', '0000:00:0a.0' ] 593: 594: In the domU an "xpci" device will show up, to which one or more pci 595: buses will attach. Then the PCI drivers will attach to PCI buses as 596: usual. Note that the default NetBSD DOMU kernels do not have "xpci" 597: or any PCI drivers built in by default; you have to build your own 598: kernel to use PCI devices in a domU. Here's a kernel config example; 599: note that only the "xpci" lines are unusual. 600: 601: include "arch/i386/conf/XEN3_DOMU" 602: 603: # Add support for PCI buses to the XEN3_DOMU kernel 604: xpci* at xenbus ? 605: pci* at xpci ? 606: 607: # PCI USB controllers 608: uhci* at pci? dev ? function ? # Universal Host Controller (Intel) 609: 610: # USB bus support 611: usb* at uhci? 612: 613: # USB Hubs 614: uhub* at usb? 615: uhub* at uhub? port ? configuration ? interface ? 616: 617: # USB Mass Storage 618: umass* at uhub? port ? configuration ? interface ? 619: wd* at umass? 620: # SCSI controllers 621: ahc* at pci? dev ? function ? # Adaptec [23]94x, aic78x0 SCSI 622: 623: # SCSI bus support (for both ahc and umass) 624: scsibus* at scsi? 625: 626: # SCSI devices 627: sd* at scsibus? target ? lun ? # SCSI disk drives 628: cd* at scsibus? target ? lun ? # SCSI CD-ROM drives 629: 630: 631: # Specific Issues 632: 633: ## domU 634: 635: [NetBSD 5 is known to panic.](http://mail-index.netbsd.org/port-xen/2018/04/17/msg009181.html) 636: (However, NetBSD 5 systems should be updated to a supported version.) 637: 638: # NetBSD as a domU in a VPS 639: 640: The bulk of the HOWTO is about using NetBSD as a dom0 on your own 641: hardware. This section explains how to deal with Xen in a domU as a 642: virtual private server where you do not control or have access to the 643: dom0. This is not intended to be an exhaustive list of VPS providers; 644: only a few are mentioned that specifically support NetBSD. 645: 646: VPS operators provide varying degrees of access and mechanisms for 647: configuration. The big issue is usually how one controls which kernel 648: is booted, because the kernel is nominally in the dom0 file system (to 649: which VPS users do not normally have access). A second issue is how 650: to install NetBSD. 651: A VPS user may want to compile a kernel for security updates, to run 652: npf, run IPsec, or any other reason why someone would want to change 653: their kernel. 654: 655: One approach is to have an administrative interface to upload a kernel, 656: or to select from a prepopulated list. Other approaches are pygrub 657: (deprecated) and pvgrub, which are ways to have a bootloader obtain a 658: kernel from the domU file system. This is closer to a regular physical 659: computer, where someone who controls a machine can replace the kernel. 660: 661: A second issue is multiple CPUs. With NetBSD 6, domUs support 662: multiple vcpus, and it is typical for VPS providers to enable multiple 663: CPUs for NetBSD domUs. 664: 665: pvgrub 666: ------ 667: 668: pvgrub is a version of grub that uses PV operations instead of BIOS 669: calls. It is booted from the dom0 as the domU kernel, and then reads 670: /grub/menu.lst and loads a kernel from the domU file system. 671: 672: [Panix](http://www.panix.com/) lets users use pvgrub. Panix reports 673: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes 674: (and hence with defaults from "newfs -O 2"). See [Panix's pvgrub 675: page](http://www.panix.com/v-colo/grub.html), which describes only 676: Linux but should be updated to cover NetBSD :-). 677: 678: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot 679: their own kernel. See then [prgmr.com NetBSD 680: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU) 681: (which is in need of updating). 682: 683: It appears that [grub's FFS 684: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c) 685: does not support all aspects of modern FFS, but there are also reports 686: that FFSv2 works fine. At prgmr, typically one has an ext2 or FAT 687: partition for the kernel with the intent that grub can understand it, 688: which leads to /netbsd not being the actual kernel. One must remember 689: to update the special boot partition. 690: 691: pygrub 692: ------- 693: 694: pygrub runs in the dom0 and looks into the domU file system. This 695: implies that the domU must have a kernel in a file system in a format 696: known to pygrub. 697: 698: pygrub doesn't seem to work to load Linux images under NetBSD dom0, 699: and is inherently less secure than pvgrub due to running inside dom0. For both these 700: reasons, pygrub should not be used, and is only still present so that 701: historical DomU images using it still work. 702: 703: As of 2014, pygrub seems to be of mostly historical 704: interest. New DomUs should use pvgrub. 705: 706: Amazon 707: ------ 708: 709: See the [Amazon EC2 page](/amazon_ec2/).