Re: [PATCH] docs: Introducing pseries documentation.

[Leonardo Augusto Guimarães Garcia]

Hi Cédric,

On 11/18/21 05:57, Cédric Le Goater wrote:
> Hello Leonardo,
>
> On 11/17/21 21:14, lagar...@linux.ibm.com wrote:
>> From: Leonardo Garcia 
>>
>> 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 
>
>
> Thanks for this update,
>
> Some general comments,
>
> There are other ppc documents :
>
>   docs/specs/ppc-spapr-hcalls.txt
>   docs/specs/ppc-spapr-hotplug.txt
>   docs/specs/ppc-spapr-numa.rst
>   docs/specs/ppc-spapr-uv-hcalls.txt
>   docs/specs/ppc-spapr-xive.rst
>   docs/specs/ppc-xive.rst
>
> that should be moved maybe and/or referenced by this file ? Feel free
> to do a follow up.


Definitely! Thanks for pointing this out. I have included some reference
to these files in v2, but proper reference will need some rework on the
above files as well (such as transforming txt files into rst files).
I'll work on that as a follow up.


>
> On the terminology, I think we should use in the text :
>
>    pSeries, PowerNV, POWER[0-9]


Sure. I updated the terminology according to the above in v2.


>
> When it comes to QEMU machines names, it's 'pseries', 'powernv'
>
> Some small comments,
>
>
>> ---
>>   docs/system/ppc/pseries.rst | 185 
>>   1 file changed, 185 insertions(+)
>>
>> diff --git a/docs/system/ppc/pseries.rst b/docs/system/ppc/pseries.rst
>> index 932d4dd17d..2de3fb4d51 100644
>> --- a/docs/system/ppc/pseries.rst
>> +++ b/docs/system/ppc/pseries.rst
>> @@ -1,12 +1,197 @@
>>   pSeries family boards (``pseries``)
>>   ===
>>   +The Power machine virtualized environment described by the `Linux
>> on Power
>
> para-virtualized ?


Absolutely. Fixed.


>
>> +Architecture Reference document (LoPAR)
>> +`_
>>
>> +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.
>
> on POWER9 and above processors. Maybe we should start introducing the
> KVM-pseries term.


We can do nested virtualization with the combination of KVM-HV and
KVM-PR on POWER8 machines, for instance. At this point of the text, I
wouldn't like to enter in this kind of detail, as it will be treated
later in the documentation.


>
>> +
>>   Supported devices
>>   -
>>   + * Multi processor support for many Power processors generations:
>> POWER5+,
>> +   POWER7, POWER7+, POWER8, POWER8NVL, Power9, and Power10 (there is
>> no support
>> +   for POWER6 processors).
>
> POWER8NVL is for baremetal only.


You can actually create pseries guests on a POWER8NVL machine using
QEMU/KVM.


>
>> + * 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 `_ (Slimline Open Firmware) is an
>> +implementation of the `IEEE 1275-1994, Standard for Boot
>> (Initialization
>> +Configuration) Firmware: Core Requirements and Practices
>> +`_.
>> +
>> +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 
>> +
>> +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 

Re: [PATCH] docs: Introducing pseries documentation.

[Leonardo Augusto Guimarães Garcia]

On 11/17/21 20:30, David Gibson wrote:
> On Wed, Nov 17, 2021 at 05:14:30PM -0300, lagar...@linux.ibm.com wrote:
>> From: Leonardo Garcia 
>>
>> 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 
> LGTM,
>
> Reviewed-by: David Gibson 


Thanks for the review.


Minor comments below.


>
> Couple of minor points below.
>
>> ---
>>  docs/system/ppc/pseries.rst | 185 
>>  1 file changed, 185 insertions(+)
>>
>> diff --git a/docs/system/ppc/pseries.rst b/docs/system/ppc/pseries.rst
>> index 932d4dd17d..2de3fb4d51 100644
>> --- a/docs/system/ppc/pseries.rst
>> +++ b/docs/system/ppc/pseries.rst
>> @@ -1,12 +1,197 @@
>>  pSeries family boards (``pseries``)
>>  ===
>>  
>> +The Power machine virtualized environment described by the `Linux on Power
>> +Architecture Reference document (LoPAR)
>> +`_
>> +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: POWER5+,
>> +   POWER7, POWER7+, POWER8, POWER8NVL, Power9, and Power10 (there is no 
>> support
>> +   for POWER6 processors).
> I wouldn't trust the POWER5+ cpu emulation with pseries; only POWER7
> and later has been tested at all.  Actually.. I wouldn't trust the
> POWER5+ CPU emulation much at all, if it's been tested, it's not for a
> long, long time.


Sure. Removed POWER5+ from the list of supported processors and put a
note saying that the code is there but the state is unknown in v2.


>> + * 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 `_ (Slimline Open Firmware) is an
>> +implementation of the `IEEE 1275-1994, Standard for Boot (Initialization
>> +Configuration) Firmware: Core Requirements and Practices
>> +`_.
>> +
>> +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 
>> +
>> +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
>> +  `_ for details).
>> +
>> +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) 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 a NVRAM device
>> +(``spapr-nvram``), so it is not needed to add this manually. However, 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=,format=raw`` to set the default 

Re: [PATCH] docs: Introducing pseries documentation.

[Cédric Le Goater]

Hello Leonardo,

On 11/17/21 21:14, lagar...@linux.ibm.com wrote:

From: Leonardo Garcia 

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 



Thanks for this update,

Some general comments,

There are other ppc documents :

  docs/specs/ppc-spapr-hcalls.txt
  docs/specs/ppc-spapr-hotplug.txt
  docs/specs/ppc-spapr-numa.rst
  docs/specs/ppc-spapr-uv-hcalls.txt
  docs/specs/ppc-spapr-xive.rst
  docs/specs/ppc-xive.rst

that should be moved maybe and/or referenced by this file ? Feel free
to do a follow up.

On the terminology, I think we should use in the text :

   pSeries, PowerNV, POWER[0-9]

When it comes to QEMU machines names, it's 'pseries', 'powernv'

Some small comments,



---
  docs/system/ppc/pseries.rst | 185 
  1 file changed, 185 insertions(+)

diff --git a/docs/system/ppc/pseries.rst b/docs/system/ppc/pseries.rst
index 932d4dd17d..2de3fb4d51 100644
--- a/docs/system/ppc/pseries.rst
+++ b/docs/system/ppc/pseries.rst
@@ -1,12 +1,197 @@
  pSeries family boards (``pseries``)
  ===
  
+The Power machine virtualized environment described by the `Linux on Power


para-virtualized ?


+Architecture Reference document (LoPAR)
+`_
+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.


on POWER9 and above processors. Maybe we should start introducing the
KVM-pseries term.


+
  Supported devices
  -
  
+ * Multi processor support for many Power processors generations: POWER5+,

+   POWER7, POWER7+, POWER8, POWER8NVL, Power9, and Power10 (there is no support
+   for POWER6 processors).


POWER8NVL is for baremetal only.


+ * 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 `_ (Slimline Open Firmware) is an
+implementation of the `IEEE 1275-1994, Standard for Boot (Initialization
+Configuration) Firmware: Core Requirements and Practices
+`_.
+
+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 
+
+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
+  `_ for details).


spapr-vty and tpm.


+
+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) 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 a NVRAM device
+(``spapr-nvram``), so it is not needed to add this manually. 


also a spapr-vty and a spapr-pci-host-bridge


However, 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=,format=raw`` to set the default PFLASH
+device, or specify one with an ID
+(``-drive if=none,file=,format=raw,id=pfid``) and pass that 

Re: [PATCH] docs: Introducing pseries documentation.

[Cédric Le Goater]

+ * Multi processor support for many Power processors generations: POWER5+,
+   POWER7, POWER7+, POWER8, POWER8NVL, Power9, and Power10 (there is no support
+   for POWER6 processors).


I wouldn't trust the POWER5+ cpu emulation with pseries; only POWER7
and later has been tested at all.  Actually.. I wouldn't trust the
POWER5+ CPU emulation much at all, if it's been tested, it's not for a
long, long time.


SLOF starts and gets a machine check but it's alive.

Thanks,

C.

Re: [PATCH] docs: Introducing pseries documentation.

[David Gibson]

On Wed, Nov 17, 2021 at 05:14:30PM -0300, lagar...@linux.ibm.com wrote:
> From: Leonardo Garcia 
> 
> 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 

LGTM,

Reviewed-by: David Gibson 

Couple of minor points below.

> ---
>  docs/system/ppc/pseries.rst | 185 
>  1 file changed, 185 insertions(+)
> 
> diff --git a/docs/system/ppc/pseries.rst b/docs/system/ppc/pseries.rst
> index 932d4dd17d..2de3fb4d51 100644
> --- a/docs/system/ppc/pseries.rst
> +++ b/docs/system/ppc/pseries.rst
> @@ -1,12 +1,197 @@
>  pSeries family boards (``pseries``)
>  ===
>  
> +The Power machine virtualized environment described by the `Linux on Power
> +Architecture Reference document (LoPAR)
> +`_
> +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: POWER5+,
> +   POWER7, POWER7+, POWER8, POWER8NVL, Power9, and Power10 (there is no 
> support
> +   for POWER6 processors).

I wouldn't trust the POWER5+ cpu emulation with pseries; only POWER7
and later has been tested at all.  Actually.. I wouldn't trust the
POWER5+ CPU emulation much at all, if it's been tested, it's not for a
long, long time.

> + * 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 `_ (Slimline Open Firmware) is an
> +implementation of the `IEEE 1275-1994, Standard for Boot (Initialization
> +Configuration) Firmware: Core Requirements and Practices
> +`_.
> +
> +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 
> +
> +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
> +  `_ for details).
> +
> +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) 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 a NVRAM device
> +(``spapr-nvram``), so it is not needed to add this manually. However, 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=,format=raw`` to set the default PFLASH
> +device, or specify one with an ID
> +(``-drive if=none,file=,format=raw,id=pfid``) and pass that ID to 
> the
> +NVRAM device with ``-global spapr-nvram.drive=pfid``.
> +
> +Switching between the KVM-PR and KVM-HV kernel module
> +-
> +
> +Currently, there are two implementations of KVM on Power, ``

[PATCH] docs: Introducing pseries documentation.

[lagarcia]

From: Leonardo Garcia 

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 
---
 docs/system/ppc/pseries.rst | 185 
 1 file changed, 185 insertions(+)

diff --git a/docs/system/ppc/pseries.rst b/docs/system/ppc/pseries.rst
index 932d4dd17d..2de3fb4d51 100644
--- a/docs/system/ppc/pseries.rst
+++ b/docs/system/ppc/pseries.rst
@@ -1,12 +1,197 @@
 pSeries family boards (``pseries``)
 ===
 
+The Power machine virtualized environment described by the `Linux on Power
+Architecture Reference document (LoPAR)
+`_
+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: POWER5+,
+   POWER7, POWER7+, POWER8, POWER8NVL, Power9, and Power10 (there is no support
+   for POWER6 processors).
+ * 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 `_ (Slimline Open Firmware) is an
+implementation of the `IEEE 1275-1994, Standard for Boot (Initialization
+Configuration) Firmware: Core Requirements and Practices
+`_.
+
+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 
+
+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
+  `_ for details).
+
+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) 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 a NVRAM device
+(``spapr-nvram``), so it is not needed to add this manually. However, 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=,format=raw`` to set the default PFLASH
+device, or specify one with an ID
+(``-drive if=none,file=,format=raw,id=pfid``) and pass that ID to the
+NVRAM device with ``-global spapr-nvram.drive=pfid``.
+
+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