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version 1.80, 2015/01/17 13:04:01	version 1.94, 2015/03/05 13:38:10
Line 92 reasonable although trailing-edge choice	Line 92 reasonable although trailing-edge choice
xenkernel42 provides Xen 4.2. This is maintained by Xen, but old as	xenkernel42 provides Xen 4.2. This is maintained by Xen, but old as
of 2014-12.	of 2014-12.

	xenkernel45 provides Xen 4.5. This is new to pkgsrc as of 2015-01 and
	not yet recommended for other than experimental/testing use.

Ideally newer versions of Xen will be added to pkgsrc.	Ideally newer versions of Xen will be added to pkgsrc.

Note that NetBSD support is called XEN3. It works with 3.1 through	Note that NetBSD support is called XEN3. It works with Xen 3 and Xen
4.2 because the hypercall interface has been stable.	4 because the hypercall interface has been stable.

Xen command program	Xen command program
-------------------	-------------------
Line 139 running an i386 NetBSD kernel as a domU,	Line 142 running an i386 NetBSD kernel as a domU,
(Note that emacs (at least) fails if run on i386 with PAE when built	(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.)	without, and vice versa, presumably due to bugs in the undump code.)

	Stability
	---------

	Mostly, NetBSD as a dom0 or domU is quite stable.
	However, there are some open PRs indicating problems.

	- [PR 48125](http://gnats.netbsd.org/48125)
	- [PR 47720](http://gnats.netbsd.org/47720)

	Note also that there are issues with sparse vnd(4) instances, but
	these are not about Xen.

Recommendation	Recommendation
--------------	--------------

Line 211 dom0 is what the computer would have bee	Line 226 dom0 is what the computer would have bee
desktop or laptop. Then, one can run domUs at will. Purists will	desktop or laptop. Then, one can run domUs at will. Purists will
deride this as less secure than the previous approach, and for a	deride this as less secure than the previous approach, and for a
computer whose purpose is to run domUs, they are right. But Xen and a	computer whose purpose is to run domUs, they are right. But Xen and a
dom0 (without domUs) is not meaingfully less secure than the same	dom0 (without domUs) is not meaningfully less secure than the same
things running without Xen. One can boot Xen or boot regular NetBSD	things running without Xen. One can boot Xen or boot regular NetBSD
alternately with little problems, simply refraining from starting the	alternately with little problems, simply refraining from starting the
Xen daemons when not running Xen.	Xen daemons when not running Xen.
Line 236 over a RAID1 header to find /boot from a	Line 251 over a RAID1 header to find /boot from a
partition; this is no different when booting Xen.	partition; this is no different when booting Xen.

There are 4 styles of providing backing storage for the virtual disks	There are 4 styles of providing backing storage for the virtual disks
used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN,	used by domUs: raw partitions, LVM, file-backed vnd(4), and SAN.

With raw partitions, one has a disklabel (or gpt) partition sized for	With raw partitions, one has a disklabel (or gpt) partition sized for
each virtual disk to be used by the domU. (If you are able to predict	each virtual disk to be used by the domU. (If you are able to predict
Line 309 starting at 0). In an attempt to add pe	Line 324 starting at 0). In an attempt to add pe
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. TODO: benchmark this.

	Xen has [many boot
	options](http://xenbits.xenproject.org/docs/4.5-testing/misc/xen-command-line.html),
	and other tham dom0 memory and max_vcpus, they are generally not
	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) and fallback versions of the non-Xen	kernel that works without Xen) and fallback versions of the non-Xen
kernel, Xen, and the dom0 kernel.	kernel, Xen, and the dom0 kernel.
Line 341 to configure the dom0 tools. The daemon	Line 361 to configure the dom0 tools. The daemon
with Xen version and with whether one is using xm or xl. Note that	with Xen version and with whether one is using xm or xl. Note that
xend is for supporting "xm", and should only be used if you plan on	xend is for supporting "xm", and should only be used if you plan on
using "xm". Do NOT enable xend if you plan on using "xl" as it will	using "xm". Do NOT enable xend if you plan on using "xl" as it will
cause problems.	cause problems. Running xl without xencommons=YES (and starting it)
	will result in a hang (so don't do that; follow the HOWTO!).

The installation of NetBSD should already have created devices for xen	The installation of NetBSD should already have created devices for xen
(xencons, xenevt), but if they are not present, create them:	(xencons, xenevt), but if they are not present, create them:
Line 374 For 4.2 with xl, add to rc.conf:	Line 395 For 4.2 with xl, add to rc.conf:
xencommons=YES	xencommons=YES
TODO: explain if there is a xend replacement	TODO: explain if there is a xend replacement

	For 4.5 (and thus with xl), add to rc.conf:

	xencommons=YES
	TODO: explain if there is a xend replacement

TODO: Recommend for/against xen-watchdog.	TODO: Recommend for/against xen-watchdog.

After you have configured the daemons and either started them (in the	After you have configured the daemons and either started them (in the
Line 389 available resources, and running domains	Line 415 available resources, and running domains
Domain-0 0 64 0 r---- 58.1	Domain-0 0 64 0 r---- 58.1

With xl, the commands are the same, and the output may be slightly	With xl, the commands are the same, and the output may be slightly
different. TODO: add example output for xl, after confirming on 4.2	different. TODO: add example output for xl before the xm example,
and resolving the TODO about rc.conf.	after confirming on 4.2 and resolving the TODO about rc.conf.

anita (for testing NetBSD)	### Issues with xencommons
--------------------------

With the setup so far, one should be able to run anita (see	xencommons starts xenstored, which stores data on behalf of dom0 and
pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as root,	domUs. It does not currently work to stop and start xenstored.
because anita must create a domU):	Certainly all domUs should be shutdown first, following the sort order
	of the rc.d scripts. However, the dom0 sets up state with xenstored,
	and is not notified when xenstored exits, leading to not recreating
	the state when the new xenstored starts. Until there's a mechanism to
	make this work, one should not expect to be able to restart xenstored
	(and thus xencommons). There is currently no reason to expect that
	this will get fixed any time soon.

anita --vmm=xm test file:///usr/obj/i386/	anita (for testing NetBSD)
	--------------------------
Alternatively, one can use --vmm=xl to use xl-based domU creation instead.
TODO: check this, and make the example use xl when confirmed.

	With the setup so far (assuming 4.2/xl), one should be able to run
	anita (see pkgsrc/misc/py-anita) to test NetBSD releases, by doing (as
	root, because anita must create a domU):

	anita --vmm=xl test file:///usr/obj/i386/

	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.

Xen-specific NetBSD issues	Xen-specific NetBSD issues
--------------------------	--------------------------

Line 477 correct set of daemons. Ensure that the	Line 515 correct set of daemons. Ensure that the
for the new version.	for the new version.


	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](http://gnats.netbsd.org/47720) for a problem with dom0
	shutdown.

Unprivileged domains (domU)	Unprivileged domains (domU)
===========================	===========================

Line 537 domain, and see if it has finished stopp	Line 594 domain, and see if it has finished stopp
xm console foo	xm console foo
xm create -c foo	xm create -c foo
xm shutdown foo	xm shutdown foo
xm list	xm list

Typing ^] will exit the console session. Shutting down a domain is	Typing ^] will exit the console session. Shutting down a domain is
equivalent to pushing the power button; a NetBSD domU will receive a	equivalent to pushing the power button; a NetBSD domU will receive a
Line 597 create an empty 4G virtual disk, simply	Line 654 create an empty 4G virtual disk, simply

dd if=/dev/zero of=foo-xbd0 bs=1m count=4096	dd if=/dev/zero of=foo-xbd0 bs=1m count=4096

	Do not use qemu-img-xen, because this will create sparse file. There
	have been recent (2015) reports of sparse vnd(4) devices causing
	lockups, but there is apparently no PR.

With the lvm style, one creates logical devices. They are then used	With the lvm style, one creates logical devices. They are then used
similarly to vnds. TODO: Add an example with lvm.	similarly to vnds. TODO: Add an example with lvm.

Line 674 shutdown, in rc.conf add:	Line 735 shutdown, in rc.conf add:

xendomains="foo bar"	xendomains="foo bar"

TODO: Explain why 4.1 rc.d/xendomains has xl, when one should use xm	Note that earlier versions of the xentools41 xendomains rc.d scripth
on 4.1. Or fix the xentools41 package to have xm	usd xl, when one should use xm with 4.1.

Creating specific unprivileged domains (domU)	Creating specific unprivileged domains (domU)
=============================================	=============================================
Line 753 It is also desirable to add	Line 814 It is also desirable to add
in rc.conf. This way, the domain will be properly shut down if	in rc.conf. This way, the domain will be properly shut down if
`xm shutdown -R` or `xm shutdown -H` is used on the dom0.	`xm shutdown -R` or `xm shutdown -H` is used on the dom0.

	It is not strictly necessary to have a kernel (as /netbsd) in the domU
	filesystem. However, various programs (e.g. netstat) will use that
	kernel to look up symbols to read from kernel virtual memory. If
	/netbsd is not the running kernel, those lookups will fail. (This is
	not really a Xen-specific issue, but because the domU kernel is
	obtained from the dom0, it is far more likely to be out of sync or
	missing with Xen.)

Your domain should be now ready to work, enjoy.	Your domain should be now ready to work, enjoy.

Creating an unprivileged Linux domain (domU)	Creating an unprivileged Linux domain (domU)
Line 946 TODO: add link to NetBSD amazon howto.	Line 1015 TODO: add link to NetBSD amazon howto.
Using npf	Using npf
---------	---------

In standard kernels, npf is a module, and thus cannot be loadeed in a	In standard kernels, npf is a module, and thus cannot be loaded in a
DOMU kernel.	DOMU kernel.

TODO: explain how to compile npf into a custom kernel, answering (but	TODO: explain how to compile npf into a custom kernel, answering (but
Line 956 http://mail-index.netbsd.org/netbsd-user	Line 1025 http://mail-index.netbsd.org/netbsd-user
TODO items for improving NetBSD/xen	TODO items for improving NetBSD/xen
===================================	===================================

* Package Xen 4.4.	* Make the NetBSD dom0 kernel work with SMP.
* Get PCI passthrough working on Xen 4.2 (or 4.4).	* Test the Xen 4.5 packages adequately to be able to recommend them as
	the standard approach.
	* Get PCI passthrough working on Xen 4.5
* Get pvgrub into pkgsrc, either via xentools or separately.	* Get pvgrub into pkgsrc, either via xentools or separately.
* grub	* grub
* Check/add support to pkgsrc grub2 for UFS2 and arbitrary	* Check/add support to pkgsrc grub2 for UFS2 and arbitrary
Line 969 TODO items for improving NetBSD/xen	Line 1040 TODO items for improving NetBSD/xen
* Get UFS2 patches into pvgrub.	* Get UFS2 patches into pvgrub.
* Add support for PV ops to a version of /boot, and make it usable as	* Add support for PV ops to a version of /boot, and make it usable as
a kernel in Xen, similar to pvgrub.	a kernel in Xen, similar to pvgrub.
	* Solve somehow the issue with modules for GENERIC not being loadable
	in a Xen dom0 or domU kernel.

	Random pointers
	===============

	TODO: This section contains links from elsewhere not yet integrated
	into the HOWTO.

	* [Amazon EC2 (which uses Xen)](../amazon_ec2/).
	* http://www.lumbercartel.ca/library/xen/
	* http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html

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