88581cc43b
The purpose of this document is to substitute the content currently available in the QEMU wiki at [0]. This initial version does contain some additional content as well. Whenever this documentation gets upstream and is reflected in [1], the QEMU wiki will be edited to point to this documentation, so that we only need to keep it updated in one place. 0. https://wiki.qemu.org/Documentation/Platforms/POWER 1. https://qemu.readthedocs.io/en/latest/system/ppc/pseries.html Signed-off-by: Leonardo Garcia <lagarcia@br.ibm.com> Reviewed-by: David Gibson <david@gibson.dropbear.id.au> Message-Id: <66b6fdde52062fdf4f4b4dc35a9f06a899c88293.1638981899.git.lagarcia@br.ibm.com> Signed-off-by: Cédric Le Goater <clg@kaod.org>
239 lines
10 KiB
ReStructuredText
239 lines
10 KiB
ReStructuredText
pSeries family boards (``pseries``)
|
|
===================================
|
|
|
|
The Power machine para-virtualized environment described by the `Linux on Power
|
|
Architecture Reference document (LoPAR)
|
|
<https://openpowerfoundation.org/wp-content/uploads/2020/07/LoPAR-20200812.pdf>`_
|
|
is called pSeries. This environment is also known as sPAPR, System p guests, or
|
|
simply Power Linux guests (although it is capable of running other operating
|
|
systems, such as AIX).
|
|
|
|
Even though pSeries is designed to behave as a guest environment, it is also
|
|
capable of acting as a hypervisor OS, providing, on that role, nested
|
|
virtualization capabilities.
|
|
|
|
Supported devices
|
|
-----------------
|
|
|
|
* Multi processor support for many Power processors generations: POWER7,
|
|
POWER7+, POWER8, POWER8NVL, POWER9, and Power10. Support for POWER5+ exists,
|
|
but its state is unknown.
|
|
* Interrupt Controller, XICS (POWER8) and XIVE (POWER9 and Power10)
|
|
* vPHB PCIe Host bridge.
|
|
* vscsi and vnet devices, compatible with the same devices available on a
|
|
PowerVM hypervisor with VIOS managing LPARs.
|
|
* Virtio based devices.
|
|
* PCIe device pass through.
|
|
|
|
Missing devices
|
|
---------------
|
|
|
|
* SPICE support.
|
|
|
|
Firmware
|
|
--------
|
|
|
|
`SLOF <https://github.com/aik/SLOF>`_ (Slimline Open Firmware) is an
|
|
implementation of the `IEEE 1275-1994, Standard for Boot (Initialization
|
|
Configuration) Firmware: Core Requirements and Practices
|
|
<https://standards.ieee.org/standard/1275-1994.html>`_.
|
|
|
|
QEMU includes a prebuilt image of SLOF which is updated when a more recent
|
|
version is required.
|
|
|
|
Build directions
|
|
----------------
|
|
|
|
.. code-block:: bash
|
|
|
|
./configure --target-list=ppc64-softmmu && make
|
|
|
|
Running instructions
|
|
--------------------
|
|
|
|
Someone can select the pSeries machine type by running QEMU with the following
|
|
options:
|
|
|
|
.. code-block:: bash
|
|
|
|
qemu-system-ppc64 -M pseries <other QEMU arguments>
|
|
|
|
sPAPR devices
|
|
-------------
|
|
|
|
The sPAPR specification defines a set of para-virtualized devices, which are
|
|
also supported by the pSeries machine in QEMU and can be instantiated with the
|
|
``-device`` option:
|
|
|
|
* ``spapr-vlan`` : a virtual network interface.
|
|
* ``spapr-vscsi`` : a virtual SCSI disk interface.
|
|
* ``spapr-rng`` : a pseudo-device for passing random number generator data to the
|
|
guest (see the `H_RANDOM hypercall feature
|
|
<https://wiki.qemu.org/Features/HRandomHypercall>`_ for details).
|
|
* ``spapr-vty``: a virtual teletype.
|
|
* ``spapr-pci-host-bridge``: a PCI host bridge.
|
|
* ``tpm-spapr``: a Trusted Platform Module (TPM).
|
|
* ``spapr-tpm-proxy``: a TPM proxy.
|
|
|
|
These are compatible with the devices historically available for use when
|
|
running the IBM PowerVM hypervisor with LPARs.
|
|
|
|
However, since these devices have originally been specified with another
|
|
hypervisor and non-Linux guests in mind, you should use the virtio counterparts
|
|
(virtio-net, virtio-blk/scsi and virtio-rng for instance) if possible instead,
|
|
since they will most probably give you better performance with Linux guests in a
|
|
QEMU environment.
|
|
|
|
The pSeries machine in QEMU is always instantiated with the following devices:
|
|
|
|
* A NVRAM device (``spapr-nvram``).
|
|
* A virtual teletype (``spapr-vty``).
|
|
* A PCI host bridge (``spapr-pci-host-bridge``).
|
|
|
|
Hence, it is not needed to add them manually, unless you use the ``-nodefaults``
|
|
command line option in QEMU.
|
|
|
|
In the case of the default ``spapr-nvram`` device, if someone wants to make the
|
|
contents of the NVRAM device persistent, they will need to specify a PFLASH
|
|
device when starting QEMU, i.e. either use
|
|
``-drive if=pflash,file=<filename>,format=raw`` to set the default PFLASH
|
|
device, or specify one with an ID
|
|
(``-drive if=none,file=<filename>,format=raw,id=pfid``) and pass that ID to the
|
|
NVRAM device with ``-global spapr-nvram.drive=pfid``.
|
|
|
|
sPAPR specification
|
|
^^^^^^^^^^^^^^^^^^^
|
|
|
|
The main source of documentation on the sPAPR standard is the `Linux on Power
|
|
Architecture Reference document (LoPAR)
|
|
<https://openpowerfoundation.org/wp-content/uploads/2020/07/LoPAR-20200812.pdf>`_.
|
|
However, documentation specific to QEMU's implementation of the specification
|
|
can also be found in QEMU documentation:
|
|
|
|
.. toctree::
|
|
:maxdepth: 1
|
|
|
|
../../specs/ppc-spapr-numa.rst
|
|
../../specs/ppc-spapr-xive.rst
|
|
|
|
Other documentation available in QEMU docs directory:
|
|
|
|
* Hypervisor calls (a.k.a. hcalls) (``docs/specs/ppc-spapr-hcalls.txt``).
|
|
* Hot plug (``/docs/specs/ppc-spapr-hotplug.txt``).
|
|
* Hypervisor calls needed by the Ultravisor
|
|
(``/docs/specs/ppc-spapr-uv-hcalls.txt``).
|
|
|
|
Switching between the KVM-PR and KVM-HV kernel module
|
|
-----------------------------------------------------
|
|
|
|
Currently, there are two implementations of KVM on Power, ``kvm_hv.ko`` and
|
|
``kvm_pr.ko``.
|
|
|
|
|
|
If a host supports both KVM modes, and both KVM kernel modules are loaded, it is
|
|
possible to switch between the two modes with the ``kvm-type`` parameter:
|
|
|
|
* Use ``qemu-system-ppc64 -M pseries,accel=kvm,kvm-type=PR`` to use the
|
|
``kvm_pr.ko`` kernel module.
|
|
* Use ``qemu-system-ppc64 -M pseries,accel=kvm,kvm-type=HV`` to use ``kvm_hv.ko``
|
|
instead.
|
|
|
|
KVM-PR
|
|
^^^^^^
|
|
|
|
KVM-PR uses the so-called **PR**\ oblem state of the PPC CPUs to run the guests,
|
|
i.e. the virtual machine is run in user mode and all privileged instructions
|
|
trap and have to be emulated by the host. That means you can run KVM-PR inside
|
|
a pSeries guest (or a PowerVM LPAR for that matter), and that is where it has
|
|
originated, as historically (prior to POWER7) it was not possible to run Linux
|
|
on hypervisor mode on a Power processor (this function was restricted to
|
|
PowerVM, the IBM proprietary hypervisor).
|
|
|
|
Because all privileged instructions are trapped, guests that use a lot of
|
|
privileged instructions run quite slow with KVM-PR. On the other hand, because
|
|
of that, this kernel module can run on pretty much every PPC hardware, and is
|
|
able to emulate a lot of guests CPUs. This module can even be used to run other
|
|
PowerPC guests like an emulated PowerMac.
|
|
|
|
As KVM-PR can be run inside a pSeries guest, it can also provide nested
|
|
virtualization capabilities (i.e. running a guest from within a guest).
|
|
|
|
It is important to notice that, as KVM-HV provides a much better execution
|
|
performance, maintenance work has been much more focused on it in the past
|
|
years. Maintenance for KVM-PR has been minimal.
|
|
|
|
In order to run KVM-PR guests with POWER9 processors, someone will need to start
|
|
QEMU with ``kernel_irqchip=off`` command line option.
|
|
|
|
KVM-HV
|
|
^^^^^^
|
|
|
|
KVM-HV uses the hypervisor mode of more recent Power processors, that allow
|
|
access to the bare metal hardware directly. Although POWER7 had this capability,
|
|
it was only starting with POWER8 that this was officially supported by IBM.
|
|
|
|
Originally, KVM-HV was only available when running on a PowerNV platform (a.k.a.
|
|
Power bare metal). Although it runs on a PowerNV platform, it can only be used
|
|
to start pSeries guests. As the pSeries guest doesn't have access to the
|
|
hypervisor mode of the Power CPU, it wasn't possible to run KVM-HV on a guest.
|
|
This limitation has been lifted, and now it is possible to run KVM-HV inside
|
|
pSeries guests as well, making nested virtualization possible with KVM-HV.
|
|
|
|
As KVM-HV has access to privileged instructions, guests that use a lot of these
|
|
can run much faster than with KVM-PR. On the other hand, the guest CPU has to be
|
|
of the same type as the host CPU this way, e.g. it is not possible to specify an
|
|
embedded PPC CPU for the guest with KVM-HV. However, there is at least the
|
|
possibility to run the guest in a backward-compatibility mode of the previous
|
|
CPUs generations, e.g. you can run a POWER7 guest on a POWER8 host by using
|
|
``-cpu POWER8,compat=power7`` as parameter to QEMU.
|
|
|
|
Modules support
|
|
---------------
|
|
|
|
As noticed in the sections above, each module can run in a different
|
|
environment. The following table shows with which environment each module can
|
|
run. As long as you are in a supported environment, you can run KVM-PR or KVM-HV
|
|
nested. Combinations not shown in the table are not available.
|
|
|
|
+--------------+------------+------+-------------------+----------+--------+
|
|
| Platform | Host type | Bits | Page table format | KVM-HV | KVM-PR |
|
|
+==============+============+======+===================+==========+========+
|
|
| PowerNV | bare metal | 32 | hash | no | yes |
|
|
| | | +-------------------+----------+--------+
|
|
| | | | radix | N/A | N/A |
|
|
| | +------+-------------------+----------+--------+
|
|
| | | 64 | hash | yes | yes |
|
|
| | | +-------------------+----------+--------+
|
|
| | | | radix | yes | no |
|
|
+--------------+------------+------+-------------------+----------+--------+
|
|
| pSeries [1]_ | PowerNV | 32 | hash | no | yes |
|
|
| | | +-------------------+----------+--------+
|
|
| | | | radix | N/A | N/A |
|
|
| | +------+-------------------+----------+--------+
|
|
| | | 64 | hash | no | yes |
|
|
| | | +-------------------+----------+--------+
|
|
| | | | radix | yes [2]_ | no |
|
|
| +------------+------+-------------------+----------+--------+
|
|
| | PowerVM | 32 | hash | no | yes |
|
|
| | | +-------------------+----------+--------+
|
|
| | | | radix | N/A | N/A |
|
|
| | +------+-------------------+----------+--------+
|
|
| | | 64 | hash | no | yes |
|
|
| | | +-------------------+----------+--------+
|
|
| | | | radix [3]_ | no | yes |
|
|
+--------------+------------+------+-------------------+----------+--------+
|
|
|
|
.. [1] On POWER9 DD2.1 processors, the page table format on the host and guest
|
|
must be the same.
|
|
|
|
.. [2] KVM-HV cannot run nested on POWER8 machines.
|
|
|
|
.. [3] Introduced on Power10 machines.
|
|
|
|
Maintainer contact information
|
|
------------------------------
|
|
|
|
Cédric Le Goater <clg@kaod.org>
|
|
|
|
Daniel Henrique Barboza <danielhb413@gmail.com>
|