Re: [RFC PATCH v5 025/104] KVM: TDX: Add place holder for TDX VM specific mem_enc_op ioctl

[Paolo Bonzini]

On 3/4/22 20:48, isaku.yamahata@xxxxxxxxx wrote:
> From: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
>
> Add a place holder function for TDX specific VM-scoped ioctl as mem_enc_op.
> TDX specific sub-commands will be added to retrieve/pass TDX specific
> parameters.
>
> KVM_MEMORY_ENCRYPT_OP was introduced for VM-scoped operations specific for
> guest state-protected VM.  It defined subcommands for technology-specific
> operations under KVM_MEMORY_ENCRYPT_OP.  Despite its name, the subcommands
> are not limited to memory encryption, but various technology-specific
> operations are defined.  It's natural to repurpose KVM_MEMORY_ENCRYPT_OP
> for TDX specific operations and define subcommands.
>
> TDX requires VM-scoped, and VCPU-scoped TDX-specific operations for device
> model, for example, qemu.  Getting system-wide parameters, TDX-specific VM
> initialization, and TDX-specific vCPU initialization.  Which requires KVM
> vCPU-scoped operations in addition to the existing VM-scoped operations.
>
> Signed-off-by: Isaku Yamahata <isaku.yamahata@xxxxxxxxx>
> ---
>   arch/x86/include/uapi/asm/kvm.h       | 11 +++++++++++
>   arch/x86/kvm/vmx/main.c               | 10 ++++++++++
>   arch/x86/kvm/vmx/tdx.c                | 24 ++++++++++++++++++++++++
>   arch/x86/kvm/vmx/x86_ops.h            |  4 ++++
>   tools/arch/x86/include/uapi/asm/kvm.h | 11 +++++++++++
>   5 files changed, 60 insertions(+)
>
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 71a5851475e7..2ad61caf4e0b 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -528,4 +528,15 @@ struct kvm_pmu_event_filter {
>   #define KVM_X86_DEFAULT_VM	0
>   #define KVM_X86_TDX_VM		1
>   
> +/* Trust Domain eXtension sub-ioctl() commands. */
> +enum kvm_tdx_cmd_id {
> +	KVM_TDX_CMD_NR_MAX,
> +};
> +
> +struct kvm_tdx_cmd {
> +	__u32 id;
> +	__u32 metadata;
> +	__u64 data;
> +};

Please include some initial documentation here already, for example it 
is not clear what "metadata" is.

Also please add

	u32 error;
	u32 unused;

for two reasons: 1) consistency with kvm_sev_cmd 2) error codes should 
be returned to userspace and not just sent through pr_tdx_error.

Paolo