--- wikisrc/ports/xen/howto.mdwn 2018/09/05 09:25:10 1.159 +++ wikisrc/ports/xen/howto.mdwn 2020/11/13 20:40:04 1.176 @@ -8,21 +8,29 @@ systems which operate in an unprivileged from the domU systems are forwarded by the Xen hypervisor to the dom0 to be fulfilled. -Xen supports different styles of guest: +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. [[!table data=""" Style of guest |Supported by NetBSD PV |Yes (dom0, domU) HVM |Yes (domU) -PVHVM |No -PVH |No +PVHVM |current-only (domU) +PVHv2 |current-only (domU, dom0 not yet) """]] In Para-Virtualized (PV) mode, the guest OS does not attempt to access hardware directly, but instead makes hypercalls to the hypervisor; PV -guests must be specifically coded for Xen. In HVM mode, no guest -modification is required; however, hardware support is required, such -as VT-x on Intel CPUs and SVM on AMD CPUs. +guests must be specifically coded for Xen. + +In HVM mode, no guest modification is required; however, hardware +support is required, such as VT-x on Intel CPUs and SVM on AMD CPUs. + +In PVHVM mode, the guest runs as HVM, but additionally can use PV +drivers for efficiency. + +In PVHv2H mode, operation is similar to PVHVM, except that qemu is not +run and thus the PV interfaces for console, disks, networking are the +only way to access these resources. 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 @@ -33,12 +41,9 @@ architecture, with installing NetBSD on installing software from pkgsrc. See also the [Xen website](http://www.xenproject.org/). -This HOWTO attempts to address both the case of running a NetBSD dom0 -on hardware and running domUs under it (NetBSD and other), and also -running NetBSD as a domU in a VPS. +[[!toc]] -Versions and Support -==================== +# Versions and Support In NetBSD, Xen is provided in pkgsrc, via matching pairs of packages xenkernel and xentools. We will refer only to the kernel versions, @@ -48,12 +53,9 @@ matching versions. Versions available in pkgsrc: [[!table data=""" -Xen Version |Package Name |Xen CPU Support |EOL'ed By Upstream -4.2 |xenkernel42 |32bit, 64bit |Yes -4.5 |xenkernel45 |64bit |Yes -4.6 |xenkernel46 |64bit |Partially -4.8 |xenkernel48 |64bit |No -4.11 |xenkernel411 |64bit |No +Xen Version |Package Name |Xen CPU Support |xm? |EOL'ed By Upstream +4.11 |xenkernel411 |x86_64 | |No +4.13 |xenkernel413 |x86_64 | |No """]] See also the [Xen Security Advisory page](http://xenbits.xen.org/xsa/). @@ -66,28 +68,24 @@ dom0 |No domU |Yes """]] -Note: NetBSD support is called XEN3. However, it does support Xen 4, +Note: NetBSD support is called XEN3. However, it does support Xen 4, because the hypercall interface has remained identical. +Older Xen had a python-based management tool called xm, now replaced +by xl. + Architecture ------------ -Xen itself runs on x86_64 hardware. +Xen 4.5 and later runs on x86_64 hardware (the NetBSD amd64 port). +There is a concept of Xen running on ARM, but there are no reports of this working with NetBSD. -The dom0 system, plus each domU, can be either i386PAE or amd64. -i386 without PAE is not supported. +The dom0 system should be amd64. (Instructions for i386PAE dom0 have been removed from the HOWTO.) -The standard approach is to use NetBSD/amd64 for the dom0. +The domU can be i386PAE or amd64. +i386PAE at one point was considered as [faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) than amd64. -To use an i386PAE dom0, one must build or obtain a 64bit Xen kernel and -install it on the system. - -For domUs, i386PAE is considered as -[faster](https://lists.xen.org/archives/html/xen-devel/2012-07/msg00085.html) -than amd64. - -NetBSD as a dom0 -================ +# Creating a dom0 In order to install a NetBSD as a dom0, one must first install a normal NetBSD system, and then pivot the install to a dom0 install by changing @@ -269,8 +267,7 @@ Minor version upgrades are trivial. Jus xenkernel version and copy the new xen.gz to `/` (where `/boot.cfg` references it), and reboot. -Unprivileged domains (domU) -=========================== +#Unprivileged domains (domU) This section describes general concepts about domUs. It does not address specific domU operating systems or how to install them. The @@ -288,8 +285,8 @@ the dom0. NetBSD's /dev/random system w Config files ------------ -See /usr/pkg/share/examples/xen/xlexample*, -for a large number of well-commented examples, mostly for running +See /usr/pkg/share/examples/xen/xlexample* +for a small number of well-commented examples, mostly for running GNU/Linux. The following is an example minimal domain configuration file. The domU @@ -313,17 +310,17 @@ are stored in files and Xen attaches the dom0 on domain creation. The system treats xbd0 as the boot device without needing explicit configuration. -By default, `xl` looks for domain config files 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 take the name of a domain. Examples of commands: [[!template id=programlisting text=""" -xl create foo -xl console foo -xl create -c foo -xl shutdown foo +xl create /usr/pkg/etc/xen/foo +xl console domU-id +xl create -c /usr/pkg/etc/xen/foo +xl shutdown domU-id xl list """]] @@ -335,7 +332,7 @@ will trigger controlled shutdowns of all CPU and memory -------------- -A domain is provided with some number of vcpus, less than the number +A domain is provided with some number of vcpus, up to the number of CPUs seen by the hypervisor. For a domU, it is controlled from the config file by the "vcpus = N" directive. @@ -353,8 +350,8 @@ Virtual disks In domU config files, the disks are defined as a sequence of 3-tuples: * The first element is "method:/path/to/disk". Common methods are - "file:" for file-backed vnd, and "phy:" for something that is already - a device. + "file:" for a file-backed vnd, and "phy:" for something that is already + a device, such as an LVM logical volume. * The second element is an artifact of how virtual disks are passed to Linux, and a source of confusion with NetBSD Xen usage. Linux domUs @@ -429,8 +426,7 @@ down cleanly on dom0 shutdown, add the f xendomains="domU-netbsd domU-linux" """]] -Creating a domU -=============== +#Creating a domU Creating domUs is almost entirely independent of operating system. We have already presented the basics of config files. Note that you must @@ -440,7 +436,7 @@ Creating a NetBSD domU ---------------------- See the earlier config file, and adjust memory. Decide on how much -storage you will provide, and prepare it (file or lvm). +storage you will provide, and prepare it (file or LVM). While the kernel will be obtained from the dom0 file system, the same file should be present in the domU as /netbsd so that tools like @@ -463,7 +459,7 @@ kernel to / and change the kernel line i kernel = "/home/bouyer/netbsd-INSTALL_XEN3_DOMU" -Then, start the domain as "xl create -c configname". +Then, start the domain as "xl create -c configfile". Alternatively, if you want to install NetBSD/Xen with a CDROM image, the following line should be used in the config file. @@ -629,8 +625,14 @@ note that only the "xpci" lines are unus cd* at scsibus? target ? lun ? # SCSI CD-ROM drives -NetBSD as a domU in a VPS -========================= +# Specific Issues + +## domU + +[NetBSD 5 is known to panic.](http://mail-index.netbsd.org/port-xen/2018/04/17/msg009181.html) +(However, NetBSD 5 systems should be updated to a supported version.) + +# NetBSD as a domU in a VPS The bulk of the HOWTO is about using NetBSD as a dom0 on your own hardware. This section explains how to deal with Xen in a domU as a @@ -657,14 +659,6 @@ A second issue is multiple CPUs. With N multiple vcpus, and it is typical for VPS providers to enable multiple CPUs for NetBSD domUs. -pygrub -------- - -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 -known to pygrub. As of 2014, pygrub seems to be of mostly historical -interest. - pvgrub ------ @@ -691,17 +685,22 @@ partition for the kernel with the intent which leads to /netbsd not being the actual kernel. One must remember to update the special boot partition. -Amazon ------- +pygrub +------- -See the [Amazon EC2 page](/amazon_ec2/). +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 +known to pygrub. + +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 +reasons, pygrub should not be used, and is only still present so that +historical DomU images using it still work. -Random pointers -=============== +As of 2014, pygrub seems to be of mostly historical +interest. New DomUs should use pvgrub. -This section contains links from elsewhere not yet integrated into the -HOWTO, and other guides. +Amazon +------ -* http://www.lumbercartel.ca/library/xen/ -* http://pbraun.nethence.com/doc/sysutils/xen_netbsd_dom0.html -* https://gmplib.org/~tege/xen.html +See the [Amazon EC2 page](/amazon_ec2/).