Re: [PATCH 1/2] docs: kvm: add documentation for KVM_CAP_S390_DIAG318

[Janosch Frank <frankja@linux.ibm.com>]

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On 6/24/20 10:21 PM, Collin Walling wrote:
> Documentation for the s390 DIAGNOSE 0x318 instruction handling.
> 
> Signed-off-by: Collin Walling <walling@linux.ibm.com>
> ---
>  Documentation/virt/kvm/api.rst | 19 +++++++++++++++++++
>  1 file changed, 19 insertions(+)
> 
> diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
> index 426f94582b7a..056608e8f243 100644
> --- a/Documentation/virt/kvm/api.rst
> +++ b/Documentation/virt/kvm/api.rst
> @@ -6150,3 +6150,22 @@ KVM can therefore start protected VMs.
>  This capability governs the KVM_S390_PV_COMMAND ioctl and the
>  KVM_MP_STATE_LOAD MP_STATE. KVM_SET_MP_STATE can fail for protected
>  guests when the state change is invalid.
> +
> +8.24 KVM_CAP_S390_DIAG318
> +-------------------------
> +
> +:Architecture: s390
> +
> +This capability allows for information regarding the control program that may
> +be observed via system/firmware service events. The availability of this

I'm not sure if control program is understood universally, it's a rather
old term to say guest kernel.

How about:

This capability allows a guest to set information about its control
program (i.e. guest kernel type and version). The information is helpful
on system/firmware service events, providing additional data about what
environments are running on the machine.


> +capability indicates that KVM handling of the register synchronization, reset,
> +and VSIE shadowing of the DIAGNOSE 0x318 related information is present.
> +
> +The information associated with the instruction is an 8-byte value consisting
> +of a one-byte Control Program Name Code (CPNC), and a 7-byte Control Program
> +Version Code (CPVC). The CPNC determines what environment the control program
> +is running in (e.g. Linux, z/VM...), and the CPVC is used for extraneous
> +information specific to OS (e.g. Linux version, Linux distribution...)
> +
> +If this capability is available, then the CPNC and CPVC can be synchronized
> +between KVM and userspace via the sync regs mechanism (KVM_SYNC_DIAG318).
> 



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