Re: [PATCH v7 3/3] s390/kvm: diagnose 0x318 get/set handling

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On 16.05.20 00:19, Collin Walling wrote:
> DIAGNOSE 0x318 (diag 318) sets information regarding the environment
> the VM is running in (Linux, z/VM, etc) and is observed via
> firmware/service events.
> 
> This is a privileged s390x instruction that must be intercepted by
> SIE. Userspace handling is required, so let's introduce some functions
> to communicate between userspace and KVM via ioctls. These will be used
> to get/set the diag 318 related information.
> 
> The Control Program Name Code (CPNC) is stored in the SIE block. The
> CPNC along with the Control Program Version Code (CPVC) are stored in
> the kvm_arch struct.
> 
> Signed-off-by: Collin Walling <walling@xxxxxxxxxxxxx>
> ---
>  Documentation/virt/kvm/devices/vm.rst | 21 +++++++
>  arch/s390/include/asm/kvm_host.h      |  5 +-
>  arch/s390/include/uapi/asm/kvm.h      |  4 ++
>  arch/s390/kvm/kvm-s390.c              | 82 +++++++++++++++++++++++++++
>  arch/s390/kvm/vsie.c                  |  2 +
>  5 files changed, 113 insertions(+), 1 deletion(-)
> 
> diff --git a/Documentation/virt/kvm/devices/vm.rst b/Documentation/virt/kvm/devices/vm.rst
> index 0aa5b1cfd700..52cc906dd7bd 100644
> --- a/Documentation/virt/kvm/devices/vm.rst
> +++ b/Documentation/virt/kvm/devices/vm.rst
> @@ -314,3 +314,24 @@ Allows userspace to query the status of migration mode.
>  	     if it is enabled
>  :Returns:   -EFAULT if the given address is not accessible from kernel space;
>  	    0 in case of success.
> +
> +6. GROUP: KVM_S390_VM_MISC
> +==========================
> +
> +:Architectures: s390
> +
> +6.1. KVM_S390_VM_MISC_DIAG_318 (r/w)
> +-----------------------------------
> +
> +Allows userspace to retrieve and set the DIAGNOSE 0x318 information,
> +which consists of a 1-byte "Control Program Name Code" and a 7-byte
> +"Control Program Version Code" (a 64 bit value all in all). This
> +information is set by the guest (usually during IPL). This interface is
> +intended to allow retrieving and setting it during migration; while no
> +real harm is done if the information is changed outside of migration,
> +it is strongly discouraged.
> +
> +:Parameters: address of a buffer in user space (u64), where the
> +	     information is read from or stored into
> +:Returns:    -EFAULT if the given address is not accessible from kernel space;
> +	     0 in case of success


An alternative would be a new sync_reg value + KVM capability.





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