Re: [PATCH] docs/s390: clarify even more that cpu-topology is KVM-only

[Nina Schoetterl-Glausch]

On Thu, 2024-03-14 at 18:22 +0100, Claudio Fontana wrote:
> At least for now cpu-topology is implemented only for KVM.
> 
> We already say this, but this tries to be more explicit,
> and also show it in the examples.
> 
> This adds a new reference in the introduction that we can point to,
> whenever we need to reference accelerators and how to select them.
> 
> Signed-off-by: Claudio Fontana <cfontana@suse.de>

Reviewed-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
Tested-by: Nina Schoetterl-Glausch <nsg@linux.ibm.com>
(meaning I ran make html)

> ---
>  docs/system/introduction.rst       |  2 ++
>  docs/system/s390x/cpu-topology.rst | 14 ++++++++------
>  2 files changed, 10 insertions(+), 6 deletions(-)
> 
> diff --git a/docs/system/introduction.rst b/docs/system/introduction.rst
> index 51ac132d6c..746707eb00 100644
> --- a/docs/system/introduction.rst
> +++ b/docs/system/introduction.rst
> @@ -1,6 +1,8 @@
>  Introduction
>  ============
>  
> +.. _Accelerators:
> +
>  Virtualisation Accelerators
>  ---------------------------
>  
> diff --git a/docs/system/s390x/cpu-topology.rst 
> b/docs/system/s390x/cpu-topology.rst
> index 5133fdc362..ca344e273c 100644
> --- a/docs/system/s390x/cpu-topology.rst
> +++ b/docs/system/s390x/cpu-topology.rst
> @@ -25,17 +25,19 @@ monitor polarization changes, see 
> ``docs/devel/s390-cpu-topology.rst``.
>  Prerequisites
>  -------------
>  
> -To use the CPU topology, you need to run with KVM on a s390x host that
> -uses the Linux kernel v6.0 or newer (which provide the so-called
> +To use the CPU topology, you currently need to choose the KVM accelerator.
> +See :ref:`Accelerators` for more details about accelerators and how to 
> select them.
> +
> +The s390x host needs to use a Linux kernel v6.0 or newer (which provides the 
> so-called
>  ``KVM_CAP_S390_CPU_TOPOLOGY`` capability that allows QEMU to signal the
>  CPU topology facility via the so-called STFLE bit 11 to the VM).
>  
>  Enabling CPU topology
>  ---------------------
>  
> -Currently, CPU topology is only enabled in the host model by default.
> +Currently, CPU topology is enabled by default only in the "host" cpu model.
>  
> -Enabling CPU topology in a CPU model is done by setting the CPU flag
> +Enabling CPU topology in another CPU model is done by setting the CPU flag
>  ``ctop`` to ``on`` as in:
>  
>  .. code-block:: bash
> @@ -132,7 +134,7 @@ In the following machine we define 8 sockets with 4 cores 
> each.
>  
>  .. code-block:: bash
>  
> -  $ qemu-system-s390x -m 2G \
> +  $ qemu-system-s390x -accel kvm -m 2G \
>      -cpu gen16b,ctop=on \
>      -smp cpus=5,sockets=8,cores=4,maxcpus=32 \
>      -device host-s390x-cpu,core-id=14 \
> @@ -227,7 +229,7 @@ with vertical high entitlement.
>  
>  .. code-block:: bash
>  
> -  $ qemu-system-s390x -m 2G \
> +  $ qemu-system-s390x -accel kvm -m 2G \
>      -cpu gen16b,ctop=on \
>      -smp cpus=1,sockets=8,cores=4,maxcpus=32 \
>      \