Re: [PATCH v15 06/11] s390x/cpu topology: interception of PTF instruction

[Thomas Huth <thuth@redhat.com>]

On 01/02/2023 14.20, Pierre Morel wrote:
> When the host supports the CPU topology facility, the PTF
> instruction with function code 2 is interpreted by the SIE,
> provided that the userland hypervizor activates the interpretation

s/hypervizor/hypervisor/

> by using the KVM_CAP_S390_CPU_TOPOLOGY KVM extension.
> 
> The PTF instructions with function code 0 and 1 are intercepted
> and must be emulated by the userland hypervizor.

dito

> During RESET all CPU of the configuration are placed in
> horizontal polarity.
> 
> Signed-off-by: Pierre Morel <pmorel@linux.ibm.com>
> ---
...
>   /**
>    * s390_topology_reset:
>    *
>    * Generic reset for CPU topology, calls s390_topology_reset()
>    * s390_topology_reset() to reset the kernel Modified Topology
>    * change record.
> + * Then set global and all CPUs polarity to POLARITY_HORIZONTAL.

You describe here already what's going to happen...

>    */
>   void s390_topology_reset(void)
>   {
>       s390_cpu_topology_reset();
> +    /* Set global polarity to POLARITY_HORIZONTAL */

... then here again ...

> +    s390_topology.polarity = POLARITY_HORIZONTAL;

... and the code is (fortunately) also very self-exaplaining...

> +    /* Set all CPU polarity to POLARITY_HORIZONTAL */
> +    s390_topology_set_cpus_polarity(POLARITY_HORIZONTAL);

... so I'd rather drop the two comments within the function body.

>   }

(rest of the patch looks fine to me)

  Thomas