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rototill to 4.13 from earlier as recommended

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: This HOWTO presumes a basic familiarity with the Xen system 12: architecture, with installing NetBSD on amd64 hardware, and with 13: installing software from pkgsrc. See also the [Xen 14: website](http://www.xenproject.org/). 15: 16: [[!toc]] 17: 18: # Overview 19: 20: The basic concept of Xen is that the hypervisor (xenkernel) runs on 21: the hardware, and runs a privileged domain ("dom0") that can access 22: disks/networking/etc. One then runs additonal unprivileged domains 23: (each a "domU"), presumably to do something useful. 24: 25: This HOWTO addresses how to run a NetBSD dom0 (and hence also build 26: xen itself). It also addresses how to run domUs in that environment, 27: and how to deal with having a domU in a Xen environment run by someone 28: else and/or not running NetBSD. 29: 30: There are many choices one can make; the HOWTO recommends the standard 31: approach and limits discussion of alternatives in many cases. 32: 33: ## Guest Styles 34: 35: Xen supports different styles of guests. 36: 37: [[!table data=""" 38: Style of guest |Supported by NetBSD 39: PV |Yes (dom0, domU) 40: HVM |Yes (domU) 41: PVHVM |current-only (domU) 42: PVH |current-only (domU, dom0 not yet) 43: """]] 44: 45: In Para-Virtualized (PV) mode, the guest OS does not attempt to access 46: hardware directly, but instead makes hypercalls to the hypervisor; PV 47: guests must be specifically coded for Xen. 48: See [PV](https://wiki.xen.org/wiki/Paravirtualization_(PV\)). 49: 50: In HVM mode, no guest modification is required; however, hardware 51: support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs. 52: The dom0 runs qemu to emulate hardware. 53: 54: In PVHVM mode, the guest runs as HVM, but additionally can use PV 55: drivers for efficiency. 56: See [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM). 57: 58: There have been two PVH modes: original PVH and PVHv2. Original PVH 59: was based on PV mode and is no longer relevant at all. PVHv2 is 60: basically lightweight HVM with PV drivers. A critical feature of it 61: is that qemu is not needed; the hypervisor can do the emulation that 62: is required. Thus, a dom0 can be PVHv2. 63: The source code uses PVH and config files use pvh; this refers to PVHv2. 64: See [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu). 65: 66: At system boot, the dom0 kernel is loaded as a module with Xen as the kernel. 67: The dom0 can start one or more domUs. (Booting is explained in detail 68: in the dom0 section.) 69: 70: ## CPU Architecture 71: 72: Xen runs on x86_64 hardware (the NetBSD amd64 port). 73: 74: There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD. 75: 76: The dom0 system should be amd64. (Instructions for i386PAE dom0 have been removed from the HOWTO.) 77: 78: The domU can be i386PAE or amd64. 79: i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64. 80: 81: ## Xen Versions 82: 83: In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages 84: xenkernel and xentools. We will refer only to the kernel versions, 85: but note that both packages must be installed together and must have 86: matching versions. 87: 88: Versions available in pkgsrc: 89: 90: [[!table data=""" 91: Xen Version |Package Name |Xen CPU Support |EOL'ed By Upstream 92: 4.11 |xenkernel411 |x86_64 |No 93: 4.13 |xenkernel413 |x86_64 |No 94: """]] 95: 96: See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/). 97: 98: Older Xen had a python-based management tool called xm, now replaced 99: by xl. 100: 101: ## NetBSD versions 102: 103: Xen has been supported in NetBSD for a long time, at least since 2005. 104: Initially Xen was PV only. 105: 106: NetBSD 8 and up support PV and HVM modes. 107: 108: Support for PVHVM and PVH is available only in NetBSD-current. 109: 110: NetBSD as a dom0 does not run SMP, because some drivers are not yet 111: safe for this. \todo Link to more information about what needs work. 112: 113: NetBSD, when run as a domU, can and does typically run SMP. 114: 115: Note: NetBSD support is called XEN3. However, it does support Xen 4, 116: because the hypercall interface has remained identical. 117: 118: # Creating a dom0 119: 120: In order to install a NetBSD as a dom0, one must first install a normal 121: NetBSD system, and then pivot the install to a dom0 install by changing 122: the kernel and boot configuration. 123: 124: In 2018-05, trouble booting a dom0 was reported with 256M of RAM: with 125: 512M it worked reliably. This does not make sense, but if you see 126: "not ELF" after Xen boots, try increasing dom0 RAM. 127: 128: ## Installation of NetBSD 129: 130: [Install NetBSD/amd64](/guide/inst/) 131: just as you would if you were not using Xen. 132: Therefore, use the most recent release, or a build from the most recent stable branch. 133: 134: ## Installation of Xen 135: 136: Use the most recent version of Xen in pkgsrc, unless the DESCR says that it ss not suitable. 137: Therefore, choose 4.13. 138: In the dom0, install xenkernel413 and xentools413 from pkgsrc. 139: 140: Once this is done, copy the Xen kernel from where pkgsrc puts it to 141: where the boot process will be able to find it: 142: 143: [[!template id=programlisting text=""" 144: # cp -p /usr/pkg/xen413-kernel/xen.gz / 145: """]] 146: 147: Then, place a NetBSD XEN3_DOM0 kernel in the `/` directory. Such kernel 148: can either be compiled manually, or downloaded from the NetBSD FTP, for 149: example at: 150: 151: [[!template id=programlisting text=""" 152: ftp.netbsd.org/pub/NetBSD/NetBSD-9.1/amd64/binary/kernel/netbsd-XEN3_DOM0.gz 153: """]] 154: 155: Add a line to /boot.cfg to boot Xen: 156: 157: [[!template id=filecontent name="/boot.cfg" text=""" 158: menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M 159: """]] 160: 161: This specifies that the dom0 should have 512MB of ram, leaving the rest 162: to be allocated for domUs. To use a serial console, use: 163: 164: [[!template id=filecontent name="/boot.cfg" text=""" 165: menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1 166: """]] 167: 168: which will use the first serial port for Xen (which counts starting 169: from 1, unlike NetBSD which counts starting from 0), forcing 170: speed/parity. Because the NetBSD command line lacks a 171: "console=pc" argument, it will use the default "xencons" console device, 172: which directs the console I/O through Xen to the same console device Xen 173: itself uses (in this case, the serial port). 174: 175: In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`, 176: to force only one vcpu to be provided (since NetBSD dom0 can't use 177: more) and to pin that vcpu to a physical CPU. Xen has 178: [many boot options](http://xenbits.xenproject.org/docs/4.13-testing/misc/xen-command-line.html), 179: and other than dom0 memory and max_vcpus, they are generally not 180: necessary. 181: 182: Ensure that the boot scripts installed in 183: `/usr/pkg/share/examples/rc.d` are in `/etc/rc.d`, either because you 184: have `PKG_RCD_SCRIPTS=yes`, or manually. (This is not special to Xen, 185: but a normal part of pkgsrc usage.) 186: 187: Set `xencommons=YES` in rc.conf: 188: 189: [[!template id=filecontent name="/etc/rc.conf" text=""" 190: xencommons=YES 191: """]] 192: 193: Now, reboot so that you are running a DOM0 kernel under Xen, rather 194: than GENERIC without Xen. 195: 196: TODO: Recommend for/against xen-watchdog. 197: 198: Once the reboot is done, use `xl` to inspect Xen's boot messages, 199: available resources, and running domains. For example: 200: 201: [[!template id=programlisting text=""" 202: # xl dmesg 203: ... xen's boot info ... 204: # xl info 205: ... available memory, etc ... 206: # xl list 207: Name Id Mem(MB) CPU State Time(s) Console 208: Domain-0 0 64 0 r---- 58.1 209: """]] 210: 211: Xen logs will be in /var/log/xen. 212: 213: ### Issues with xencommons 214: 215: `xencommons` starts `xenstored`, which stores data on behalf of dom0 and 216: domUs. It does not currently work to stop and start xenstored. 217: Certainly all domUs should be shutdown first, following the sort order 218: of the rc.d scripts. However, the dom0 sets up state with xenstored, 219: and is not notified when xenstored exits, leading to not recreating 220: the state when the new xenstored starts. Until there's a mechanism to 221: make this work, one should not expect to be able to restart xenstored 222: (and thus xencommons). There is currently no reason to expect that 223: this will get fixed any time soon. 224: 225: ## anita (for testing NetBSD) 226: 227: With the setup so far, one should be able to run 228: anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as 229: root, because anita must create a domU): 230: 231: [[!template id=programlisting text=""" 232: anita --vmm=xl test file:///usr/obj/i386/ 233: """]] 234: 235: ## Xen-specific NetBSD issues 236: 237: There are (at least) two additional things different about NetBSD as a 238: dom0 kernel compared to hardware. 239: 240: One is that the module ABI is different because some of the #defines 241: change, so one must build modules for Xen. As of netbsd-7, the build 242: system does this automatically. 243: 244: The other difference is that XEN3_DOM0 does not have exactly the same 245: options as GENERIC. While it is debatable whether or not this is a 246: bug, users should be aware of this and can simply add missing config 247: items if desired. 248: 249: ## Updating NetBSD in a dom0 250: 251: This is just like updating NetBSD on bare hardware, assuming the new 252: version supports the version of Xen you are running. Generally, one 253: replaces the kernel and reboots, and then overlays userland binaries 254: and adjusts `/etc`. 255: 256: Note that one must update both the non-Xen kernel typically used for 257: rescue purposes and the DOM0 kernel used with Xen. 258: 259: ## Converting from grub to /boot 260: 261: These instructions were used to convert a system from 262: grub to /boot. The system was originally installed in February of 263: 2006 with a RAID1 setup and grub to boot Xen 2, and has been updated 264: over time. Before these commands, it was running NetBSD 6 i386, Xen 265: 4.1 and grub, much like the message linked earlier in the grub 266: section. 267: 268: [[!template id=programlisting text=""" 269: # Install MBR bootblocks on both disks. 270: fdisk -i /dev/rwd0d 271: fdisk -i /dev/rwd1d 272: # Install NetBSD primary boot loader (/ is FFSv1) into RAID1 components. 273: installboot -v /dev/rwd0d /usr/mdec/bootxx_ffsv1 274: installboot -v /dev/rwd1d /usr/mdec/bootxx_ffsv1 275: # Install secondary boot loader 276: cp -p /usr/mdec/boot / 277: # Create boot.cfg following earlier guidance: 278: menu=Xen:load /netbsd-XEN3PAE_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M 279: menu=Xen.ok:load /netbsd-XEN3PAE_DOM0.ok.gz console=pc;multiboot /xen.ok.gz dom0_mem=512M 280: menu=GENERIC:boot 281: menu=GENERIC single-user:boot -s 282: menu=GENERIC.ok:boot netbsd.ok 283: menu=GENERIC.ok single-user:boot netbsd.ok -s 284: menu=Drop to boot prompt:prompt 285: default=1 286: timeout=30 287: """]] 288: 289: ## Upgrading Xen versions 290: 291: Minor version upgrades are trivial. Just rebuild/replace the 292: xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg` 293: references it), and reboot. 294: 295: #Unprivileged domains (domU) 296: 297: This section describes general concepts about domUs. It does not 298: address specific domU operating systems or how to install them. The 299: config files for domUs are typically in `/usr/pkg/etc/xen`, and are 300: typically named so that the file name, domU name and the domU's host 301: name match. 302: 303: The domU is provided with CPU and memory by Xen, configured by the 304: dom0. The domU is provided with disk and network by the dom0, 305: mediated by Xen, and configured in the dom0. 306: 307: Entropy in domUs can be an issue; physical disks and network are on 308: the dom0. NetBSD's /dev/random system works, but is often challenged. 309: 310: ## Config files 311: 312: See /usr/pkg/share/examples/xen/xlexample* 313: for a small number of well-commented examples, mostly for running 314: GNU/Linux. 315: 316: The following is an example minimal domain configuration file. The domU 317: serves as a network file server. 318: 319: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text=""" 320: name = "domU-id" 321: kernel = "/netbsd-XEN3PAE_DOMU-i386-foo.gz" 322: memory = 1024 323: vif = [ 'mac=aa:00:00:d1:00:09,bridge=bridge0' ] 324: disk = [ 'file:/n0/xen/foo-wd0,0x0,w', 325: 'file:/n0/xen/foo-wd1,0x1,w' ] 326: """]] 327: 328: The domain will have name given in the `name` setting. The kernel has the 329: host/domU name in it, so that on the dom0 one can update the various 330: domUs independently. The `vif` line causes an interface to be provided, 331: with a specific mac address (do not reuse MAC addresses!), in bridge 332: mode. Two disks are provided, and they are both writable; the bits 333: are stored in files and Xen attaches them to a vnd(4) device in the 334: dom0 on domain creation. The system treats xbd0 as the boot device 335: without needing explicit configuration. 336: 337: By convention, domain config files are kept in `/usr/pkg/etc/xen`. Note 338: that "xl create" takes the name of a config file, while other commands 339: take the name of a domain. 340: 341: Examples of commands: 342: 343: [[!template id=programlisting text=""" 344: xl create /usr/pkg/etc/xen/foo 345: xl console domU-id 346: xl create -c /usr/pkg/etc/xen/foo 347: xl shutdown domU-id 348: xl list 349: """]] 350: 351: Typing `^]` will exit the console session. Shutting down a domain is 352: equivalent to pushing the power button; a NetBSD domU will receive a 353: power-press event and do a clean shutdown. Shutting down the dom0 354: will trigger controlled shutdowns of all configured domUs. 355: 356: ## CPU and memory 357: 358: A domain is provided with some number of vcpus, up to the number 359: of CPUs seen by the hypervisor. For a domU, it is controlled 360: from the config file by the "vcpus = N" directive. 361: 362: A domain is provided with memory; this is controlled in the config 363: file by "memory = N" (in megabytes). In the straightforward case, the 364: sum of the the memory allocated to the dom0 and all domUs must be less 365: than the available memory. 366: 367: Xen also provides a "balloon" driver, which can be used to let domains 368: use more memory temporarily. 369: 370: ## Virtual disks 371: 372: In domU config files, the disks are defined as a sequence of 3-tuples: 373: 374: * The first element is "method:/path/to/disk". Common methods are 375: "file:" for a file-backed vnd, and "phy:" for something that is already 376: a device, such as an LVM logical volume. 377: 378: * The second element is an artifact of how virtual disks are passed to 379: Linux, and a source of confusion with NetBSD Xen usage. Linux domUs 380: are given a device name to associate with the disk, and values like 381: "hda1" or "sda1" are common. In a NetBSD domU, the first disk appears 382: as xbd0, the second as xbd1, and so on. However, xl demands a 383: second argument. The name given is converted to a major/minor by 384: calling stat(2) on the name in /dev and this is passed to the domU. 385: In the general case, the dom0 and domU can be different operating 386: systems, and it is an unwarranted assumption that they have consistent 387: numbering in /dev, or even that the dom0 OS has a /dev. With NetBSD 388: as both dom0 and domU, using values of 0x0 for the first disk and 0x1 389: for the second works fine and avoids this issue. For a GNU/Linux 390: guest, one can create /dev/hda1 in /dev, or to pass 0x301 for 391: /dev/hda1. 392: 393: * The third element is "w" for writable disks, and "r" for read-only 394: disks. 395: 396: Example: 397: [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text=""" 398: disk = [ 'file:/n0/xen/foo-wd0,0x0,w' ] 399: """]] 400: 401: Note that NetBSD by default creates only vnd[0123]. If you need more 402: than 4 total virtual disks at a time, run e.g. "./MAKEDEV vnd4" in the 403: dom0. 404: 405: Note that NetBSD by default creates only xbd[0123]. If you need more 406: virtual disks in a domU, run e.g. "./MAKEDEV xbd4" in the domU. 407: 408: Virtual Networking 409: ------------------ 410: 411: Xen provides virtual Ethernets, each of which connects the dom0 and a 412: domU. For each virtual network, there is an interface "xvifN.M" in 413: the dom0, and a matching interface xennetM (NetBSD name) in domU index N. 414: The interfaces behave as if there is an Ethernet with two 415: adapters connected. From this primitive, one can construct various 416: configurations. We focus on two common and useful cases for which 417: there are existing scripts: bridging and NAT. 418: 419: With bridging (in the example above), the domU perceives itself to be 420: on the same network as the dom0. For server virtualization, this is 421: usually best. Bridging is accomplished by creating a bridge(4) device 422: and adding the dom0's physical interface and the various xvifN.0 423: interfaces to the bridge. One specifies "bridge=bridge0" in the domU 424: config file. The bridge must be set up already in the dom0; an 425: example /etc/ifconfig.bridge0 is: 426: 427: [[!template id=filecontent name="/etc/ifconfig.bridge0" text=""" 428: create 429: up 430: !brconfig bridge0 add wm0 431: """]] 432: 433: With NAT, the domU perceives itself to be behind a NAT running on the 434: dom0. This is often appropriate when running Xen on a workstation. 435: TODO: NAT appears to be configured by "vif = [ '' ]". 436: 437: The MAC address specified is the one used for the interface in the new 438: domain. The interface in dom0 will use this address XOR'd with 439: 00:00:00:01:00:00. Random MAC addresses are assigned if not given. 440: 441: Starting domains automatically 442: ------------------------------ 443: 444: To start domains `domU-netbsd` and `domU-linux` at boot and shut them 445: down cleanly on dom0 shutdown, add the following in rc.conf: 446: 447: [[!template id=filecontent name="/etc/rc.conf" text=""" 448: xendomains="domU-netbsd domU-linux" 449: """]] 450: 451: # Creating a domU 452: 453: Creating domUs is almost entirely independent of operating system. We 454: have already presented the basics of config files. Note that you must 455: have already completed the dom0 setup so that "xl list" works. 456: 457: Creating a NetBSD PV domU 458: -------------------------- 459: 460: See the earlier config file, and adjust memory. Decide on how much 461: storage you will provide, and prepare it (file or LVM). 462: 463: While the kernel will be obtained from the dom0 file system, the same 464: file should be present in the domU as /netbsd so that tools like 465: savecore(8) can work. (This is helpful but not necessary.) 466: 467: The kernel must be specifically for Xen and for use as a domU. The 468: i386 and amd64 provide the following kernels: 469: 470: i386 XEN3PAE_DOMU 471: amd64 XEN3_DOMU 472: 473: This will boot NetBSD, but this is not that useful if the disk is 474: empty. One approach is to unpack sets onto the disk outside of xen 475: (by mounting it, just as you would prepare a physical disk for a 476: system you can't run the installer on). 477: 478: A second approach is to run an INSTALL kernel, which has a miniroot 479: and can load sets from the network. To do this, copy the INSTALL 480: kernel to / and change the kernel line in the config file to: 481: 482: kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU" 483: 484: Then, start the domain as "xl create -c configfile". 485: 486: Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following 487: line should be used in the config file. 488: 489: disk = [ 'phy:/dev/wd0e,0x1,w', 'phy:/dev/cd0a,0x2,r' ] 490: 491: After booting the domain, the option to install via CDROM may be 492: selected. The CDROM device should be changed to `xbd1d`. 493: 494: Once done installing, "halt -p" the new domain (don't reboot or halt, 495: it would reload the INSTALL_XEN3_DOMU kernel even if you changed the 496: config file), switch the config file back to the XEN3_DOMU kernel, 497: and start the new domain again. Now it should be able to use "root on 498: xbd0a" and you should have a, functional NetBSD domU. 499: 500: TODO: check if this is still accurate. 501: When the new domain is booting you'll see some warnings about *wscons* 502: and the pseudo-terminals. These can be fixed by editing the files 503: `/etc/ttys` and `/etc/wscons.conf`. You must disable all terminals in 504: `/etc/ttys`, except *console*, like this: 505: 506: console "/usr/libexec/getty Pc" vt100 on secure 507: ttyE0 "/usr/libexec/getty Pc" vt220 off secure 508: ttyE1 "/usr/libexec/getty Pc" vt220 off secure 509: ttyE2 "/usr/libexec/getty Pc" vt220 off secure 510: ttyE3 "/usr/libexec/getty Pc" vt220 off secure 511: 512: Finally, all screens must be commented out from `/etc/wscons.conf`. 513: 514: It is also desirable to add 515: 516: powerd=YES 517: 518: in rc.conf. This way, the domain will be properly shut down if 519: `xl shutdown -R` or `xl shutdown -H` is used on the dom0. 520: \todo Check the translation to xl. 521: 522: It is not strictly necessary to have a kernel (as /netbsd) in the domU 523: file system. However, various programs (e.g. netstat) will use that 524: kernel to look up symbols to read from kernel virtual memory. If 525: /netbsd is not the running kernel, those lookups will fail. (This is 526: not really a Xen-specific issue, but because the domU kernel is 527: obtained from the dom0, it is far more likely to be out of sync or 528: missing with Xen.) 529: 530: Creating a Linux domU 531: --------------------- 532: 533: Creating unprivileged Linux domains isn't much different from 534: unprivileged NetBSD domains, but there are some details to know. 535: 536: First, the second parameter passed to the disk declaration (the '0x1' in 537: the example below) 538: 539: disk = [ 'phy:/dev/wd0e,0x1,w' ] 540: 541: does matter to Linux. It wants a Linux device number here (e.g. 0x300 542: for hda). Linux builds device numbers as: (major \<\< 8 + minor). 543: So, hda1 which has major 3 and minor 1 on a Linux system will have 544: device number 0x301. Alternatively, devices names can be used (hda, 545: hdb, ...) as xentools has a table to map these names to devices 546: numbers. To export a partition to a Linux guest we can use: 547: 548: disk = [ 'phy:/dev/wd0e,0x300,w' ] 549: root = "/dev/hda1 ro" 550: 551: and it will appear as /dev/hda on the Linux system, and be used as root 552: partition. 553: 554: To install the Linux system on the partition to be exported to the 555: guest domain, the following method can be used: install 556: sysutils/e2fsprogs from pkgsrc. Use mke2fs to format the partition 557: that will be the root partition of your Linux domain, and mount it. 558: Then copy the files from a working Linux system, make adjustments in 559: `/etc` (fstab, network config). It should also be possible to extract 560: binary packages such as .rpm or .deb directly to the mounted partition 561: using the appropriate tool, possibly running under NetBSD's Linux 562: emulation. Once the file system has been populated, umount it. If 563: desirable, the file system can be converted to ext3 using tune2fs -j. 564: It should now be possible to boot the Linux guest domain, using one of 565: the vmlinuz-\*-xenU kernels available in the Xen binary distribution. 566: 567: To get the Linux console right, you need to add: 568: 569: extra = "xencons=tty1" 570: 571: to your configuration since not all Linux distributions auto-attach a 572: tty to the xen console. 573: 574: ## Creating a NetBSD HVM domU 575: 576: Use type='hmv', probably. Use a GENERIC kernel within the disk image. 577: 578: ## Creating a NetBSD PVH domU 579: 580: Use type='pvh'. 581: 582: \todo Explain where the kernel comes from. 583: 584: 585: Creating a Solaris domU 586: ----------------------- 587: 588: See possibly outdated 589: [Solaris domU instructions](/ports/xen/howto-solaris/). 590: 591: 592: PCI passthrough: Using PCI devices in guest domains 593: --------------------------------------------------- 594: 595: NB: PCI passthrough only works on some Xen versions and as of 2020 it 596: is not clear that it works on any version in pkgsrc. Reports 597: confirming or denying this notion should be sent to port-xen@. 598: 599: The dom0 can give other domains access to selected PCI 600: devices. This can allow, for example, a non-privileged domain to have 601: access to a physical network interface or disk controller. However, 602: keep in mind that giving a domain access to a PCI device most likely 603: will give the domain read/write access to the whole physical memory, 604: as PCs don't have an IOMMU to restrict memory access to DMA-capable 605: device. Also, it's not possible to export ISA devices to non-dom0 606: domains, which means that the primary VGA adapter can't be exported. 607: A guest domain trying to access the VGA registers will panic. 608: 609: If the dom0 is NetBSD, it has to be running Xen 3.1, as support has 610: not been ported to later versions at this time. 611: 612: For a PCI device to be exported to a domU, is has to be attached to 613: the "pciback" driver in dom0. Devices passed to the dom0 via the 614: pciback.hide boot parameter will attach to "pciback" instead of the 615: usual driver. The list of devices is specified as "(bus:dev.func)", 616: where bus and dev are 2-digit hexadecimal numbers, and func a 617: single-digit number: 618: 619: pciback.hide=(00:0a.0)(00:06.0) 620: 621: pciback devices should show up in the dom0's boot messages, and the 622: devices should be listed in the `/kern/xen/pci` directory. 623: 624: PCI devices to be exported to a domU are listed in the "pci" array of 625: the domU's config file, with the format "0000:bus:dev.func". 626: 627: pci = [ '0000:00:06.0', '0000:00:0a.0' ] 628: 629: In the domU an "xpci" device will show up, to which one or more pci 630: buses will attach. Then the PCI drivers will attach to PCI buses as 631: usual. Note that the default NetBSD DOMU kernels do not have "xpci" 632: or any PCI drivers built in by default; you have to build your own 633: kernel to use PCI devices in a domU. Here's a kernel config example; 634: note that only the "xpci" lines are unusual. 635: 636: include "arch/i386/conf/XEN3_DOMU" 637: 638: # Add support for PCI buses to the XEN3_DOMU kernel 639: xpci* at xenbus ? 640: pci* at xpci ? 641: 642: # PCI USB controllers 643: uhci* at pci? dev ? function ? # Universal Host Controller (Intel) 644: 645: # USB bus support 646: usb* at uhci? 647: 648: # USB Hubs 649: uhub* at usb? 650: uhub* at uhub? port ? configuration ? interface ? 651: 652: # USB Mass Storage 653: umass* at uhub? port ? configuration ? interface ? 654: wd* at umass? 655: # SCSI controllers 656: ahc* at pci? dev ? function ? # Adaptec [23]94x, aic78x0 SCSI 657: 658: # SCSI bus support (for both ahc and umass) 659: scsibus* at scsi? 660: 661: # SCSI devices 662: sd* at scsibus? target ? lun ? # SCSI disk drives 663: cd* at scsibus? target ? lun ? # SCSI CD-ROM drives 664: 665: 666: # Specific Issues 667: 668: ## domU 669: 670: [NetBSD 5 is known to panic.](http://mail-index.netbsd.org/port-xen/2018/04/17/msg009181.html) 671: (However, NetBSD 5 systems should be updated to a supported version.) 672: 673: # NetBSD as a domU in a VPS 674: 675: The bulk of the HOWTO is about using NetBSD as a dom0 on your own 676: hardware. This section explains how to deal with Xen in a domU as a 677: virtual private server where you do not control or have access to the 678: dom0. This is not intended to be an exhaustive list of VPS providers; 679: only a few are mentioned that specifically support NetBSD. 680: 681: VPS operators provide varying degrees of access and mechanisms for 682: configuration. The big issue is usually how one controls which kernel 683: is booted, because the kernel is nominally in the dom0 file system (to 684: which VPS users do not normally have access). A second issue is how 685: to install NetBSD. 686: A VPS user may want to compile a kernel for security updates, to run 687: npf, run IPsec, or any other reason why someone would want to change 688: their kernel. 689: 690: One approach is to have an administrative interface to upload a kernel, 691: or to select from a prepopulated list. Other approaches are pygrub 692: (deprecated) and pvgrub, which are ways to have a bootloader obtain a 693: kernel from the domU file system. This is closer to a regular physical 694: computer, where someone who controls a machine can replace the kernel. 695: 696: A second issue is multiple CPUs. With NetBSD 6, domUs support 697: multiple vcpus, and it is typical for VPS providers to enable multiple 698: CPUs for NetBSD domUs. 699: 700: ## Complexities due to Xen changes 701: 702: Xen has many security advisories and people running Xen systems make 703: different choices. 704: 705: ### stub domains 706: 707: Some (Linux only?) dom0 systems use something called "stub domains" to 708: isolate qemu from the dom0 system, as a security and reliabilty 709: mechanism when running HVM domUs. Somehow, NetBSD's GENERIC kernel 710: ends up using PIO for disks rather than DMA. Of course, all of this 711: is emulated, but emulated PIO is unusably slow. This problem is not 712: currently understood. 713: 714: ### Grant tables 715: 716: There are multiple versions of using grant tables, and some security 717: advisories have suggested disabling some versions. Some versions of 718: NetBSD apparently only use specific versions and this can lead to 719: "NetBSD current doesn't run on hosting provider X" situations. 720: 721: \todo Explain better. 722: 723: ## Boot methods 724: 725: ### pvgrub 726: 727: pvgrub is a version of grub that uses PV operations instead of BIOS 728: calls. It is booted from the dom0 as the domU kernel, and then reads 729: /grub/menu.lst and loads a kernel from the domU file system. 730: 731: [Panix](http://www.panix.com/) lets users use pvgrub. Panix reports 732: that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes 733: (and hence with defaults from "newfs -O 2"). See [Panix's pvgrub 734: page](http://www.panix.com/v-colo/grub.html), which describes only 735: Linux but should be updated to cover NetBSD :-). 736: 737: [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot 738: their own kernel. See then [prgmr.com NetBSD 739: HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU) 740: (which is in need of updating). 741: 742: It appears that [grub's FFS 743: code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c) 744: does not support all aspects of modern FFS, but there are also reports 745: that FFSv2 works fine. At prgmr, typically one has an ext2 or FAT 746: partition for the kernel with the intent that grub can understand it, 747: which leads to /netbsd not being the actual kernel. One must remember 748: to update the special boot partition. 749: 750: ### pygrub 751: 752: pygrub runs in the dom0 and looks into the domU file system. This 753: implies that the domU must have a kernel in a file system in a format 754: known to pygrub. 755: 756: pygrub doesn't seem to work to load Linux images under NetBSD dom0, 757: and is inherently less secure than pvgrub due to running inside dom0. For both these 758: reasons, pygrub should not be used, and is only still present so that 759: historical DomU images using it still work. 760: 761: As of 2014, pygrub seems to be of mostly historical 762: interest. New DomUs should use pvgrub. 763: 764: ## Specific Providers 765: 766: ### Amazon 767: 768: See the [Amazon EC2 page](/amazon_ec2/).