Diff for /wikisrc/ports/xen/howto.mdwn between versions 1.204 and 1.205

version 1.204, 2021/03/15 00:25:54 version 1.205, 2021/03/15 23:01:56
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 ## Guest Styles  ## Guest Styles
   
 Xen supports different styles of guests.  Xen supports different styles of guests.  See
   https://wiki.xenproject.org/wiki/Virtualization_Spectrum for a
   discussion.
   
   This table shows the styles, and if a NetBSD dom0 can run in that
   style, if a NetBSD dom0 can sypport that style of guest in a domU, and
   if NetBSD as a domU can support that style.
   
 [[!table data="""  [[!table data="""
 Style of guest  |description                            |NetBSD dom0?   |NetBSD domU?  Style of guest  |dom0 can be?   |dom0 can support?      |domU can be?
 PV              |Paravirtualization (hypercalls)        |yes            |yes  PV              |yes            |yes                    |yes
 HVM             |unmodified guest - domU perceives HW   |can run guests |yes  HVM             |N/A            |yes                    |yes
 PVHVM           |Like HVM but also PV drivers           |can run guests |current only  PVHVM           |N/A            |yes                    |current only
 PVH             |Lightweight HVM (no qemu) and PV       |not yet        |current only  PVH             |not yet        |current only           |current only
 """]]  """]]
   
 In Para-Virtualized (PV) mode, the guest OS does not attempt to access  In PV (paravirtualized) mode, the guest OS does not attempt to access
 hardware directly, but instead makes hypercalls to the hypervisor; PV  hardware directly, but instead makes hypercalls to the hypervisor; PV
 guests must be specifically coded for Xen.  guests must be specifically coded for Xen.  See
 See [PV](https://wiki.xen.org/wiki/Paravirtualization_(PV\)).  [PV](https://wiki.xen.org/wiki/Paravirtualization_(PV\)).
   
 In HVM mode, no guest modification is required; however, hardware  In HVM (Hardware Virtual Machine) mode, no guest modification is
 support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs.  required.  However, hardware support is required, such as VT-x on
 The dom0 runs qemu to emulate hardware.  It is therefore non-sensical  Intel CPUs and SVM on AMD CPUs to assist with the processor emulation.
 to have an HVM dom0.  The dom0 runs qemu to emulate hardware other than the processor.  It
   is therefore non-sensical to have an HVM dom0, because there is no
   underlying system to provide emulation.
   
 In PVHVM mode, the guest runs as HVM, but additionally can use PV  In PVHVM mode, the guest runs as HVM, but additionally uses PV
 drivers for efficiency.  Therefore it is non-sensical for to have a  drivers for efficiency.  Therefore it is non-sensical for to have a
 PVHVM dom0.  See [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM).  PVHVM dom0.  See [PV on HVM](https://wiki.xen.org/wiki/PV_on_HVM).
   
 There have been two PVH modes: original PVH and PVHv2.  Original PVH  There have been two PVH modes: original PVH and PVHv2.  Original PVH
 was based on PV mode and is no longer relevant at all.  Therefore  was based on PV mode and is no longer relevant at all.  Therefore
 PVHv2 is abreviated PVH.  PVHv2 is basically lightweight HVM with PV  PVHv2 is written as PVH, here and elsewhere.  PVH is basically
 drivers.  A critical feature of it is that qemu is not needed; the  lightweight HVM with PV drivers.  A critical feature of it is that
 hypervisor can do the emulation that is required.  Thus, a dom0 can be  qemu is not needed; the hypervisor can do the emulation that is
 PVHv2.  The source code uses PVH and config files use pvh, but NB that  required.  Thus, a dom0 can be PVH.  The source code uses PVH and
 this refers to PVHv2.  See  config files use pvh, but NB that this refers to PVHv2.  See
 [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu).  [PVH(v2)](https://wiki.xenproject.org/wiki/PVH_(v2\)_Domu).
   
 At system boot, the dom0 kernel is loaded as a module with Xen as the kernel.  At system boot, the dom0 kernel is loaded as a module with Xen as the
 The dom0 can start one or more domUs.  (Booting is explained in detail  kernel.  The dom0 can start one or more domUs.  (Booting is explained
 in the dom0 section.)  in detail in the dom0 section.)
   
 ## CPU Architecture  ## CPU Architecture
   
Line 116  Initially Xen was PV only. Line 124  Initially Xen was PV only.
   
 NetBSD Xen has always supported PV, in both dom0 and domU; for a long  NetBSD Xen has always supported PV, in both dom0 and domU; for a long
 time this was the only way.  NetBSD >=8 as a dom0 supports HVM mode in  time this was the only way.  NetBSD >=8 as a dom0 supports HVM mode in
 domUs (HVM as a dom0 does not make sense).  domUs.
   
 Support for PVHVM and PVH is available only in NetBSD-current; this is  Support for PVHVM and PVH is available only in NetBSD-current; this is
 currently somewhat experimental, although PVHVM appears reasonably  currently somewhat experimental, although PVHVM appears reasonably
Line 154  In 2018-05, trouble booting a dom0 was r Line 162  In 2018-05, trouble booting a dom0 was r
 using Xen.  Therefore, use the most recent release, or a build from  using Xen.  Therefore, use the most recent release, or a build from
 the most recent stable branch.  Alternatively, use -current, being  the most recent stable branch.  Alternatively, use -current, being
 mindful of all the usual caveats of lower stability of current, and  mindful of all the usual caveats of lower stability of current, and
 likely a bit more so.  likely a bit more so.  Think about how you will provide storage for
   disk images.
   
 ## Installation of Xen  ## Installation of Xen
   
 ### Building Xen  ### Building Xen
   
 Use the most recent version of Xen in pkgsrc, unless the DESCR says that it is not suitable.  Use the most recent version of Xen in pkgsrc, unless the DESCR says
 Therefore, choose 4.13.  that it is not suitable.  Therefore, choose 4.13.  In the dom0,
 In the dom0, install xenkernel413 and xentools413 from pkgsrc.  install xenkernel413 and xentools413 from pkgsrc.
   
 Once this is done, copy the Xen kernel from where pkgsrc puts it to  Once this is done, copy the Xen kernel from where pkgsrc puts it to
 where the boot process will be able to find it:  where the boot process will be able to find it:
Line 208  wd0a causes boot to fail. Line 217  wd0a causes boot to fail.
   
 Beware that userconf statements must be attached to the dom0 load, and  Beware that userconf statements must be attached to the dom0 load, and
 may not be at top-level, because then they would try to configure the  may not be at top-level, because then they would try to configure the
 hypervisor, if there is a way to pass them via multiboot .  It appears  hypervisor, if there is a way to pass them via multiboot.  It appears
 that adding `userconf=pckbc` to `/boot.cfg` causes Xen to crash very  that adding `userconf=pckbc` to `/boot.cfg` causes Xen to crash very
 early with a heap overflow.  early with a heap overflow.
   
Line 264  messages from the hypervisor's console;  Line 273  messages from the hypervisor's console; 
   
 ### Tuning  ### Tuning
   
 In an attempt to add performance, one can also add `dom0_max_vcpus=1 dom0_vcpus_pin`,  In an attempt to add performance, one can also add `dom0_max_vcpus=1
 to force only one vcpu to be provided (since NetBSD dom0 can't use  dom0_vcpus_pin`, to force only one vcpu to be provided (since NetBSD
 more) and to pin that vcpu to a physical CPU. Xen has  dom0 can't use more) and to pin that vcpu to a physical CPU. Xen has
 [many boot options](http://xenbits.xenproject.org/docs/4.13-testing/misc/xen-command-line.html),  [many boot
   options](http://xenbits.xenproject.org/docs/4.13-testing/misc/xen-command-line.html),
 and other than dom0 memory and max_vcpus, they are generally not  and other than dom0 memory and max_vcpus, they are generally not
 necessary.  necessary.
   
 \todo Revisit this advice with current.  \todo Revisit this advice with current.
 \todo Explain if anyone has ever actually measured that this helps.  \todo Explain if anyone has ever actually measured that this helps.
   
Line 328  dom0 kernel compared to hardware. Line 339  dom0 kernel compared to hardware.
   
 One is that through NetBSD 9 the module ABI is different because some  One is that through NetBSD 9 the module ABI is different because some
 of the #defines change, so there are separate sets of modules in  of the #defines change, so there are separate sets of modules in
 /stand.  In NetBSD-current, there is only one set of modules.  /stand.  (Further, zfs in Xen is troubled because of differing
   MAXPHYS; see the zfs howto for more.)  In NetBSD-current, there is
   only one set of modules.
   
 The other difference is that XEN3_DOM0 does not have exactly the same  The other difference is that XEN3_DOM0 does not have exactly the same
 options as GENERIC.  While it is debatable whether or not this is a  options as GENERIC.  While this is roughly agreed to be in large part
 bug, users should be aware of this and can simply add missing config  a bug, users should be aware of this and can simply add missing config
 items if desired.  items if desired.
   
 Finally, there have been occasional reports of trouble with X11  Finally, there have been occasional reports of trouble with X11
 servers in NetBSD as a dom0.  servers in NetBSD as a dom0.  Some hardware support is intentionally
   disabled in XEN3_DOM0.
   
 ## Updating Xen in a dom0  ## Updating Xen in a dom0
   
Line 357  rescue purposes, as well as the DOM0 ker Line 371  rescue purposes, as well as the DOM0 ker
   
 ## anita (for testing NetBSD)  ## anita (for testing NetBSD)
   
 With a NetBSD dom0, even without any domUs, one should be able to run  With a NetBSD dom0, even without any domUs, one can run anita (see
 anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as  pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as root,
 root, because anita must create a domU):  because anita must create a domU):
   
 [[!template id=programlisting text="""  [[!template id=programlisting text="""
 anita --vmm=xl test file:///usr/obj/i386/  anita --vmm=xl test file:///usr/obj/i386/
Line 385  the dom0.  NetBSD's /dev/random system w Line 399  the dom0.  NetBSD's /dev/random system w
 See /usr/pkg/share/examples/xen/xlexample* for a very small number of  See /usr/pkg/share/examples/xen/xlexample* for a very small number of
 examples for running GNU/Linux.  examples for running GNU/Linux.
   
 The following is an example minimal domain configuration file. The domU  The following is an example minimal domain configuration file.  The
 serves as a network file server.  domU serves as a network file server.
   
 [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""  [[!template id=filecontent name="/usr/pkg/etc/xen/foo" text="""
 name = "domU-id"  name = "domU-id"
Line 406  are stored in files and Xen attaches the Line 420  are stored in files and Xen attaches the
 dom0 on domain creation.  The system treats xbd0 as the boot device  dom0 on domain creation.  The system treats xbd0 as the boot device
 without needing explicit configuration.  without needing explicit configuration.
   
 There is not type line; that implicitly defines a pv domU.  Otherwise,  There is not a type line; that implicitly defines a pv domU.
 one sets type to the lower-case version of the domU type in the table  Otherwise, one sets type to the lower-case version of the domU type in
 above, e.g. `type = "hvm"`.  the table above; see later sections.
   
 By convention, domain config files are kept in `/usr/pkg/etc/xen`.  Note  By convention, domain config files are kept in `/usr/pkg/etc/xen`.  Note
 that "xl create" takes the name of a config file, while other commands  that "xl create" takes the name of a config file, while other commands
Line 431  will trigger controlled shutdowns of all Line 445  will trigger controlled shutdowns of all
   
 ## CPU and memory  ## CPU and memory
   
 A domain is provided with some number of vcpus, up to the number  A domain is provided with some number of vcpus; any domain can have up
 of CPUs seen by the hypervisor. For a domU, it is controlled  to the number of CPUs seen by the hypervisor. For a domU, it is
 from the config file by the "vcpus = N" directive.  controlled from the config file by the "vcpus = N" directive.  It is
   normal to overcommit vcpus; a 4-core machine machine might well provide 4
   vcpus to each domU.  One might also configure fewer vcpus for a domU.
   
 A domain is provided with memory; this is controlled in the config  A domain is provided with memory; this is controlled in the config
 file by "memory = N" (in megabytes).  In the straightforward case, the  file by "memory = N" (in megabytes).  In the straightforward case, the
Line 745  note that only the "xpci" lines are unus Line 761  note that only the "xpci" lines are unus
   
 ## Nesting under Linux KVM  ## Nesting under Linux KVM
   
 It is possible to run a Xen and a NetBSD dom0 under Linux KVM.  One  It is possible to run Xen and a NetBSD dom0 under Linux KVM.  One
 can enable virtio in the dom0 for greater speed.  can enable virtio in the dom0 for greater speed.
   
   ## Nesting under qemu
   
   It is possible to run Xen and a NetBSD dom0 under qemu on NetBSD, and
   also with nvmm.
   \todo Check this.
   
 ## Other nesting  ## Other nesting
   
 In theory, any full emulation should be able to run Xen and a NetBSD  In theory, any full emulation should be able to run Xen and a NetBSD
 dom0.  The HOWTO does not currently have information about Xen XVM  dom0.  The HOWTO does not currently have information about Xen XVM
 mode, nvmm, qemu, Virtualbox, etc.  mode, Virtualbox, etc.
   
 ## NetBSD 5 as domU  ## NetBSD 5 as domU
   
Line 793  different choices. Line 815  different choices.
   
 ### stub domains  ### stub domains
   
 Some (Linux only?) dom0 systems use something called "stub domains" to  Some (Linux) dom0 systems use something called "stub domains" to
 isolate qemu from the dom0 system, as a security and reliabilty  isolate qemu from the dom0 system, as a security and reliabilty
 mechanism when running HVM domUs.  Somehow, NetBSD's GENERIC kernel  mechanism when running HVM domUs.  Somehow, NetBSD's GENERIC kernel
 ends up using PIO for disks rather than DMA.  Of course, all of this  ends up using PIO for disks rather than DMA.  Of course, all of this
Line 803  currently understood. Line 825  currently understood.
 ### Grant tables  ### Grant tables
   
 There are multiple versions of using grant tables, and some security  There are multiple versions of using grant tables, and some security
 advisories have suggested disabling some versions.  Some versions of  advisories have suggested disabling some versions.  NetBSD through 9
 NetBSD apparently only use specific versions and this can lead to  uses version 1 and NetBSD-current uses version 2.  This can lead to
 "NetBSD current doesn't run on hosting provider X" situations.  "NetBSD current doesn't run on hosting provider X" situations.
   
 \todo Explain better.  \todo Explain better.
Line 817  pvgrub is a version of grub that uses PV Line 839  pvgrub is a version of grub that uses PV
 calls.  It is booted from the dom0 as the domU kernel, and then reads  calls.  It is booted from the dom0 as the domU kernel, and then reads
 /grub/menu.lst and loads a kernel from the domU file system.  /grub/menu.lst and loads a kernel from the domU file system.
   
 [Panix](http://www.panix.com/) lets users use pvgrub.  Panix reports  
 that pvgrub works with FFsv2 with 16K/2K and 32K/4K block/frag sizes  
 (and hence with defaults from "newfs -O 2").  See [Panix's pvgrub  
 page](http://www.panix.com/v-colo/grub.html), which describes only  
 Linux but should be updated to cover NetBSD :-).  
   
 [prgmr.com](http://prgmr.com/) also lets users with pvgrub to boot  
 their own kernel.  See then [prgmr.com NetBSD  
 HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)  
 (which is in need of updating).  
   
 It appears that [grub's FFS  It appears that [grub's FFS
 code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)  code](http://xenbits.xensource.com/hg/xen-unstable.hg/file/bca284f67702/tools/libfsimage/ufs/fsys_ufs.c)
 does not support all aspects of modern FFS, but there are also reports  does not support all aspects of modern FFS, but there are also reports
 that FFSv2 works fine.  At prgmr, typically one has an ext2 or FAT  that FFSv2 works fine.
 partition for the kernel with the intent that grub can understand it,  
 which leads to /netbsd not being the actual kernel.  One must remember  
 to update the special boot partition.  
   
 ### pygrub  ### pygrub
   
   As of 2014, pygrub seems to be of mostly historical interest.  As of
   2021, the section should perhaps be outright deleted.
   
 pygrub runs in the dom0 and looks into the domU file system.  This  pygrub runs in the dom0 and looks into the domU file system.  This
 implies that the domU must have a kernel in a file system in a format  implies that the domU must have a kernel in a file system in a format
 known to pygrub.  known to pygrub.
   
 pygrub doesn't seem to work to load Linux images under NetBSD dom0,  pygrub doesn't seem to work to load Linux images under NetBSD dom0,
 and is inherently less secure than pvgrub due to running inside dom0. For both these  and is inherently less secure than pvgrub due to running inside
 reasons, pygrub should not be used, and is only still present so that  dom0. For both these reasons, pygrub should not be used, and is only
 historical DomU images using it still work.  still present so that historical DomU images using it still work.
   
 As of 2014, pygrub seems to be of mostly historical  
 interest. New DomUs should use pvgrub.  
   
 ## Specific Providers  ## Specific Providers
   
   The intent is to list providers only if they document support for
   running NetBSD, and to point to their resources briefly.
   
   ### panix.com
   
   [Panix](http://www.panix.com/) provides NetBSD as an OS option.  See
   https://www.panix.com/v-colo/nupgrade.html for some information.
   Users can use pvgrub.  Panix reports that pvgrub works with FFsv2 with
   16K/2K and 32K/4K block/frag sizes (and hence with defaults from
   "newfs -O 2").  See [Panix's pvgrub
   page](http://www.panix.com/v-colo/grub.html) which describes how to
   boot NetBSD.
   
   ### prgmr.com
   
   [prgmr.com](http://prgmr.com/) provides released versions of
   NetBSD/amd64 as installation options.  Users can use pvgrub to boot
   their own kernel, and a small FAT32 /boot is encouraged.  See the
   [prgmr.com NetBSD
   HOWTO](http://wiki.prgmr.com/mediawiki/index.php/NetBSD_as_a_DomU)
   (which is in need of updating).
   
 ### Amazon  ### Amazon
   
 See the [Amazon EC2 page](/amazon_ec2/).  See the [Amazon EC2 page](/amazon_ec2/).

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