Re: [PATCH 6/6] KVM: PPC: Document KVM_PPC_GET_COMPAT_CAPS ioctl

[Harsh Prateek Bora <harshpb@linux.ibm.com>]

On 30/04/26 11:19 am, Amit Machhiwal wrote:
> Add documentation for the KVM_PPC_GET_COMPAT_CAPS ioctl to the KVM API
> documentation.
> 
> The ioctl exposes host processor compatibility modes supported for
> nested KVM guests on PowerPC systems.
> 
> Signed-off-by: Amit Machhiwal <amachhiw@linux.ibm.com>
> ---
>   Documentation/virt/kvm/api.rst | 35 ++++++++++++++++++++++++++++++++++
>   1 file changed, 35 insertions(+)
> 
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 52bbbb553ce1..7a10c3c6cbf1 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6555,6 +6555,41 @@ KVM_S390_KEYOP_SSKE
>   
>   .. _kvm_run:
>   
> +4.145 KVM_PPC_GET_COMPAT_CAPS
> +-----------------------------
> +:Capability: KVM_CAP_PPC_COMPAT_CAPS
> +:Architectures: powerpc
> +:Type: vm ioctl
> +:Parameters: struct kvm_ppc_compat_caps (out)
> +:Returns:
> +	0 on successful completion,
> +	-EFAULT if ``struct kvm_ppc_compat_caps`` cannot be written

-EINVAL also needs to be documented?

> +
> +IBM POWER system server-based processors provide a compatibility mode feature
> +where an Nth generation processor can operate in modes consistent with earlier
> +generations such as (N-1) and (N-2).
> +
> +This ioctl provides userspace with information about the CPU compatibility modes
> +supported by the current host processor for booting the nested KVM guests on
> +PowerNV (KVM nested APIv1) and PowerVM (KVM nested APIv2) platforms.
> +
> +::
> +
> +  struct kvm_ppc_compat_caps {
> +         __u32   flags;
> +         __u64   compat_capabilities;    /* Capabilities supported by the host */
> +  };
> +
> +The ``compat_capabilities`` bit field describes the processor compatibility
> +modes supported by the host. For example, the following bits indicate support
> +for specific processor modes.
> +
> +::
> +
> + bit 1: KVM guests can run in Power9 processor mode
> + bit 2: KVM guests can run in Power10 processor mode
> + bit 3: KVM guests can run in Power11 processor mode

May be use H_GUEST_CAP_POWER9 and friends ?

> +
>   5. The kvm_run structure
>   ========================
>