Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.150 and 1.155

version 1.150, 2018/07/26 11:08:33 version 1.155, 2018/08/01 13:19:43
Line 3 Line 3
 Introduction  Introduction
 ============  ============
   
 [![[Xen  
 screenshot]](https://www.netbsd.org/gallery/in-Action/hubertf-xens.png)](https://www.netbsd.org/gallery/in-Action/hubertf-xen.png)  
   
 Xen is a hypervisor for x86 hardware, which supports running multiple guest  Xen is a hypervisor for x86 hardware, which supports running multiple guest
 operating systems on a single physical machine.  Xen is a Type 1 or  operating systems on a single physical machine.  Xen is a Type 1 or
 bare-metal hypervisor; one uses the Xen kernel to control the CPU,  bare-metal hypervisor; one uses the Xen kernel to control the CPU,
Line 31  guests must be specifically coded for Xe Line 28  guests must be specifically coded for Xe
 modification is required; however, hardware support is required, such  modification is required; however, hardware support is required, such
 as VT-x on Intel CPUs and SVM on AMD CPUs.  as VT-x on Intel CPUs and SVM on AMD CPUs.
   
 There are further features for IOMMU virtualization, Intel's VT-d and  
 AMD's AMD-Vi.  TODO: Explain whether Xen on NetBSD makes use of these  
 features.  TODO: Review by someone who really understands this.  
   
 At boot, the dom0 kernel is loaded as a module with Xen as the kernel.  At boot, the dom0 kernel is loaded as a module with Xen as the kernel.
 The dom0 can start one or more domUs.  (Booting is explained in detail  The dom0 can start one or more domUs.  (Booting is explained in detail
 in the dom0 section.)  in the dom0 section.)
Line 83  See also the [Xen Security Advisory page Line 76  See also the [Xen Security Advisory page
   
 Note: Xen 4.2 was the last version to support 32bit CPUs.  Note: Xen 4.2 was the last version to support 32bit CPUs.
   
 Xen command program  
 -------------------  
   
 Early Xen used a program called xm to manipulate the system from the  
 dom0.  Starting in 4.1, a replacement program with similar behavior  
 called xl is provided, but it does not work well in 4.1.  In 4.2, both  
 xm and xl work fine.  4.4 is the last version that has xm.  
   
 You must make a global choice to use xm or xl, because it affects not  
 only which command you use, but the command used by rc.d scripts  
 (specifically xendomains) and which daemons should be run.  The  
 xentools packages provide xl for 4.2 and up.  
   
 In 4.2, you can choose to use xm by simply changing the ctl_command  
 variable and setting xend=YES in rc.conf.  
   
 With xl, virtual devices are configured in parallel, which can cause  
 problems if they are written assuming serial operation (e.g., updating  
 firewall rules without explicit locking).  There is now locking for  
 the provided scripts, which works for normal casses (e.g, file-backed  
 xbd, where a vnd must be allocated).  But, as of 201612, it has not  
 been adequately tested for a complex custom setup with a large number  
 of interfaces.  
   
 NetBSD versions  NetBSD versions
 ---------------  ---------------
   
 The netbsd-7, netbsd-8, and -current branches are all reasonable  
 choices, with more or less the same considerations for non-Xen use.  
 NetBSD 8 is recommended as the stable version of the most recent  NetBSD 8 is recommended as the stable version of the most recent
 release for production use.  release for production use.
   
Line 128  because the hypercall interface has rema Line 95  because the hypercall interface has rema
 Architecture  Architecture
 ------------  ------------
   
 Xen itself can run on i386 (Xen < 4.2) or amd64 hardware (all Xen  Xen itself runs on amd64 hardware. Practically, almost any computer
 versions).  (Practically, almost any computer where one would want to  where one would want to run Xen today supports amd64.
 run Xen today supports amd64.)  
   The dom0 system, plus each domU, can be either i386PAE or amd64.
 Xen, the dom0 system, and each domU system can be either i386 or  i386 without PAE is not supported.
 amd64.  When building a xenkernel package, one obtains an i386 Xen  
 kernel on an i386 host, and an amd64 Xen kernel on an amd64 host.  If  The standard approach is to use NetBSD/amd64 for the dom0.  For domUs,
 the Xen kernel is i386, then the dom0 kernel and all domU kernels must  NetBSD/i386 (PAE) and NetBSD/amd64 are in widespread use, and there is
 be i386.  With an amd64 Xen kernel, an amd64 dom0 kernel is known to  
 work, and an i386 dom0 kernel should in theory work.  An amd64  
 Xen/dom0 is known to support both i386 and amd64 domUs.  
   
 i386 dom0 and domU kernels must be PAE (except for an i386 Xen 3.1  
 kernel, where one can use non-PAE for dom0 and all domUs); PAE kernels  
 are included in the NetBSD default build.  (Note that emacs (at least)  
 fails if run on i386 with PAE when built without, and vice versa,  
 presumably due to bugs in the undump code.)  
   
 Because of the above, the standard approach is to use an amd64 Xen  
 kernel and NetBSD/amd64 for the dom0.  For domUs, NetBSD/i386 (with  
 the PAE kernel) and NetBSD/amd64 are in widespread use, and there is  
 little to no Xen-specific reason to prefer one over the other.  little to no Xen-specific reason to prefer one over the other.
   
 Note that to use an i386 dom0 with Xen 4.5 or higher, one must build  Note that to use an i386 dom0 with Xen 4.5 or higher, one must build
 (or obtain from pre-built packages) an amd64 Xen kernel and install  (or obtain from pre-built packages) an amd64 Xen kernel and install
 that on the system.  (One must also use a PAE i386 kernel, but this is  that on the system.  Almost no one in the NetBSD/Xen community does
 also required with an i386 Xen kernel.).  Almost no one in the  this, and the standard, well-tested, approach is to use an amd64 dom0.
 NetBSD/Xen community does this, and the standard, well-tested,  
 approach is to use an amd64 dom0.  
   
 A [posting on  A [posting on
 xen-devel](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)  xen-devel](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html)
Line 164  explained that PV system call overhead w Line 116  explained that PV system call overhead w
 there is some notion that i386 guests are faster.  It goes on to  there is some notion that i386 guests are faster.  It goes on to
 caution that the total situation is complex and not entirely  caution that the total situation is complex and not entirely
 understood. On top of that caution, the post is about Linux, not  understood. On top of that caution, the post is about Linux, not
 NetBSD.  TODO: Include link to benchmarks, if someone posts them.  NetBSD.
   
 NetBSD as a dom0  NetBSD as a dom0
 ================  ================
Line 250  HOWTO page.) Line 202  HOWTO page.)
 Installation of Xen  Installation of Xen
 -------------------  -------------------
   
 In the dom0, install sysutils/xenkernel42 and sysutils/xentools42 from  We will consider that you chose to use Xen 4.8, with NetBSD/amd64 as
 pkgsrc (or another matching pair).  See [the pkgsrc  dom0. In the dom0, install xenkernel48 and xentools48 from pkgsrc.
 documentation](https://www.NetBSD.org/docs/pkgsrc/) for help with  Ensure that your packages are recent.
 pkgsrc.  Ensure that your packages are recent; the HOWTO does not  
 contemplate old builds.  
   
   
 For Xen 3.1, support for HVM guests is in sysutils/xentool3-hvm.  More  
 recent versions have HVM support integrated in the main xentools  
 package.  It is entirely reasonable to run only PV guests.  
   
 Next you need to install the selected Xen kernel itself, which is  
 installed by pkgsrc as "/usr/pkg/xen*-kernel/xen.gz".  Copy it to /.  
 For debugging, one may copy xen-debug.gz; this is conceptually similar  
 to DIAGNOSTIC and DEBUG in NetBSD.  xen-debug.gz is basically only  
 useful with a serial console.  Then, place a NetBSD XEN3_DOM0 kernel  
 in /, copied from releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz  
 of a NetBSD build.  If using i386, use  
 releasedir/i386/binary/kernel/netbsd-XEN3PAE_DOM0.gz.  (If using Xen  
 3.1 and i386, you may use XEN3_DOM0 with the non-PAE Xen.  But you  
 should not use Xen 3.1.)  Both xen and the NetBSD kernel may be (and  
 typically are) left compressed.  
   
 In a dom0, kernfs is mandatory for xend to communicate with the  
 kernel, so ensure that /kern is in fstab.  (A standard NetBSD install  
 should already mount /kern.)  
   
 Because you already installed NetBSD, you have a working boot setup  
 with an MBR bootblock, either bootxx_ffsv1 or bootxx_ffsv2 at the  
 beginning of your root file system, have /boot, and likely also  
 /boot.cfg.  (If not, fix before continuing!)  
   
 Add a line to to /boot.cfg to boot Xen.  See boot.cfg(5) for an  
 example.  The basic line is  
   
         menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M  Once this is done, install the Xen kernel itself:
   
   [[!template id=programlisting text="""
   # cp /usr/pkg/xen48-kernel/xen.gz /
   """]]
   
 which specifies that the dom0 should have 512M, leaving the rest to be  Then, place a NetBSD XEN3_DOM0 kernel in /, copied from
 allocated for domUs.  To use a serial console, use  releasedir/amd64/binary/kernel/netbsd-XEN3_DOM0.gz of a NetBSD build.
   
         menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1  Add a line to /boot.cfg to boot Xen:
   
   [[!template id=programlisting text="""
   menu=Xen:load /netbsd-XEN3_DOM0.gz console=pc;multiboot /xen.gz dom0_mem=512M
   """]]
   
   which specifies that the dom0 should have 512MB of ram, leaving the rest
   to be allocated for domUs.  To use a serial console, use
   
   [[!template id=programlisting text="""
   menu=Xen:load /netbsd-XEN3_DOM0.gz;multiboot /xen.gz dom0_mem=512M console=com1 com1=9600,8n1
   """]]
   
 which will use the first serial port for Xen (which counts starting  which will use the first serial port for Xen (which counts starting
 from 1, unlike NetBSD which counts starting from 0), forcing  from 1, unlike NetBSD which counts starting from 0), forcing
Line 299  speed/parity.  Because the NetBSD comman Line 235  speed/parity.  Because the NetBSD comman
 which directs the console I/O through Xen to the same console device Xen  which directs the console I/O through Xen to the same console device Xen
 itself uses (in this case, the serial port).  itself uses (in this case, the serial port).
   
 In an attempt to add performance, one can also add  In an attempt to add performance, one can also add:
   
         dom0_max_vcpus=1 dom0_vcpus_pin  [[!template id=programlisting text="""
   dom0_max_vcpus=1 dom0_vcpus_pin
   """]]
   
 to force only one vcpu to be provided (since NetBSD dom0 can't use  to force only one vcpu to be provided (since NetBSD dom0 can't use
 more) and to pin that vcpu to a physical CPU.  TODO: benchmark this.  more) and to pin that vcpu to a physical CPU.
   
 Xen has [many boot  Xen has [many boot
 options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),  options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),
Line 312  and other than dom0 memory and max_vcpus Line 250  and other than dom0 memory and max_vcpus
 necessary.  necessary.
   
 As with non-Xen systems, you should have a line to boot /netbsd (a  As with non-Xen systems, you should have a line to boot /netbsd (a
 kernel that works without Xen).  Consider a line to boot /netbsd.ok (a  kernel that works without Xen).
 fallback version of the non-Xen kernel, updated manually when you are  
 sure /netbsd is ok).  Consider also a line to boot fallback versions  
 of Xen and the dom0 kernel, but note that non-Xen NetBSD can be used  
 to resolve Xen booting issues.  
   
 Probably you want a default=N line to choose Xen in the absence of  
 intervention.  
   
 Now, reboot so that you are running a DOM0 kernel under Xen, rather  Now, reboot so that you are running a DOM0 kernel under Xen, rather
 than GENERIC without Xen.  than GENERIC without Xen.
Line 341  described above.) Line 272  described above.)
 Configuring Xen  Configuring Xen
 ---------------  ---------------
   
 Xen logs will be in /var/log/xen.  
   
 Now, you have a system that will boot Xen and the dom0 kernel, but not  Now, you have a system that will boot Xen and the dom0 kernel, but not
 do anything else special.  Make sure that you have rebooted into Xen.  do anything else special.  Make sure that you have rebooted into Xen.
 There will be no domUs, and none can be started because you still have  There will be no domUs, and none can be started because you still have
 to configure the dom0 daemons.  to configure the dom0 daemons.
   
 The daemons which should be run vary with Xen version and with whether  The daemons which should be run vary with Xen version and with whether
 one is using xm or xl.  The Xen 3.1, 3.3 and 4.1 packages use xm.  Xen  one is using xm or xl. Xen 4.2 and up packages use xl. To use xm with 4.2,
 4.2 and up packages use xl.  To use xm with 4.2, edit xendomains to  edit xendomains to use xm instead.
 use xm instead.  
   
 For 3.1 and 3.3, you should enable xend and xenbackendd:  
   
         xend=YES  
         xenbackendd=YES  
   
 For 4.1 and up, you should enable xencommons.  Not enabling xencommons  For 4.1 and up, you should enable xencommons.  Not enabling xencommons
 will result in a hang; it is necessary to hit ^C on the console to let  will result in a hang; it is necessary to hit ^C on the console to let
 the machine finish booting.  If you are using xm (default in 4.1, or  the machine finish booting.  If you are using xm (default in 4.1, or
 if you changed xendomains in 4.2), you should also enable xend:  if you changed xendomains in 4.2), you should also enable xend:
   
         xend=YES # only if using xm, and only installed <= 4.2  [[!template id=programlisting text="""
         xencommons=YES  xend=YES # only if using xm, and only installed <= 4.2
   xencommons=YES
   """]]
   
 TODO: Recommend for/against xen-watchdog.  TODO: Recommend for/against xen-watchdog.
   
Line 372  After you have configured the daemons an Line 297  After you have configured the daemons an
 order given) or rebooted, use xm or xl to inspect Xen's boot messages,  order given) or rebooted, use xm or xl to inspect Xen's boot messages,
 available resources, and running domains.  An example with xl follows:  available resources, and running domains.  An example with xl follows:
   
         # xl dmesg  [[!template id=programlisting text="""
         [xen's boot info]  # xl dmesg
         # xl info  ... xen's boot info ...
         [available memory, etc.]  # xl info
         # xl list  ... available memory, etc ...
         Name              Id  Mem(MB)  CPU  State  Time(s)  Console  # xl list
         Domain-0           0       64    0  r----     58.1  Name              Id  Mem(MB)  CPU  State  Time(s)  Console
   Domain-0           0       64    0  r----     58.1
   """]]
   
   Xen logs will be in /var/log/xen.
   
 ### Issues with xencommons  ### Issues with xencommons
   
Line 397  this will get fixed any time soon. Line 326  this will get fixed any time soon.
 The installation of NetBSD should already have created devices for xen  The installation of NetBSD should already have created devices for xen
 (xencons, xenevt, xsd_kva), but if they are not present, create them:  (xencons, xenevt, xsd_kva), but if they are not present, create them:
   
         cd /dev && sh MAKEDEV xen  [[!template id=programlisting text="""
   cd /dev && sh MAKEDEV xen
   """]]
   
 anita (for testing NetBSD)  anita (for testing NetBSD)
 --------------------------  --------------------------
Line 406  With the setup so far (assuming 4.2/xl), Line 337  With the setup so far (assuming 4.2/xl),
 anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as  anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
 root, because anita must create a domU):  root, because anita must create a domU):
   
         anita --vmm=xl test file:///usr/obj/i386/  [[!template id=programlisting text="""
   anita --vmm=xl test file:///usr/obj/i386/
   """]]
   
 Alternatively, one can use --vmm=xm to use xm-based domU creation  Alternatively, one can use --vmm=xm to use xm-based domU creation
 instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.  instead (and must, on Xen <= 4.1).   TODO: confirm that anita xl really works.
Line 495  Specifically, for 4.x remove autorestart Line 428  Specifically, for 4.x remove autorestart
 are specified with numbers as the second argument, as the examples  are specified with numbers as the second argument, as the examples
 above show, and not NetBSD device names.  above show, and not NetBSD device names.
   
 Hardware known to work  
 ----------------------  
   
 Arguably, this section is misplaced, and there should be a page of  
 hardware that runs NetBSD/amd64 well, with the mostly-well-founded  
 assumption that NetBSD/xen runs fine on any modern hardware that  
 NetBSD/amd64 runs well on.  Until then, we give motherboard/CPU (and  
 sometimes RAM) pairs/triples to aid those choosing a motherboard.  
 Note that Xen systems usually do not run X, so a listing here does not  
 imply that X works at all.  
   
         Supermicro X9SRL-F, Xeon E5-1650 v2, 96 GiB ECC  
         Supermicro ??, Atom C2758 (8 core), 32 GiB ECC  
         ASUS M5A78L-M/USB3 AM3+ microATX, AMD Piledriver X8 4000MHz, 16 GiB ECC  
   
 Older hardware:  
   
         Intel D915GEV, Pentium4 CPU 3.40GHz, 4GB 533MHz Synchronous DDR2  
         INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU     E6850  @ 3.00GHz"  
         INTEL DG33FB, "Intel(R) Core(TM)2 Duo CPU     E8400  @ 3.00GHz"  
   
 Running Xen under qemu  
 ----------------------  
   
 The astute reader will note that this section is somewhat twisted.  
 However, it can be useful to run Xen under qemu either because the  
 version of NetBSD as a dom0 does not run on the hardware in use, or to  
 generate automated test cases involving Xen.  
   
 In 2015-01, the following combination was reported to mostly work:  
   
         host OS: NetBSD/amd64 6.1.4  
         qemu: 2.2.0 from pkgsrc  
         Xen kernel: xenkernel42-4.2.5nb1 from pkgsrc  
         dom0 kernel: NetBSD/amd64 6.1.5  
         Xen tools: xentools42-4.2.5 from pkgsrc  
   
 See [PR 47720](https://gnats.netbsd.org/47720) for a problem with dom0  
 shutdown.  
   
 Unprivileged domains (domU)  Unprivileged domains (domU)
 ===========================  ===========================
   
Line 767  savecore(8) can work.   (This is helpful Line 660  savecore(8) can work.   (This is helpful
 The kernel must be specifically for Xen and for use as a domU.  The  The kernel must be specifically for Xen and for use as a domU.  The
 i386 and amd64 provide the following kernels:  i386 and amd64 provide the following kernels:
   
         i386 XEN3_DOMU  
         i386 XEN3PAE_DOMU          i386 XEN3PAE_DOMU
         amd64 XEN3_DOMU          amd64 XEN3_DOMU
   
 Unless using Xen 3.1 (and you shouldn't) with i386-mode Xen, you must  
 use the PAE version of the i386 kernel.  
   
 This will boot NetBSD, but this is not that useful if the disk is  This will boot NetBSD, but this is not that useful if the disk is
 empty.  One approach is to unpack sets onto the disk outside of xen  empty.  One approach is to unpack sets onto the disk outside of xen
 (by mounting it, just as you would prepare a physical disk for a  (by mounting it, just as you would prepare a physical disk for a

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