Re: [PATCH 18/30] KVM: TDX: Add place holder for TDX VM specific mem_enc_op ioctl

["Huang, Kai" <kai.huang@intel.com>]

On Thu, 2025-02-20 at 12:05 -0500, Paolo Bonzini wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
> 
> 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.
> 
> 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.  Make mem_enc_ioctl non-optional as it's always filled.
> 
> Signed-off-by: Isaku Yamahata <isaku.yamahata@intel.com>
> Co-developed-by: Tony Lindgren <tony.lindgren@linux.intel.com>
> Signed-off-by: Tony Lindgren <tony.lindgren@linux.intel.com>
> Signed-off-by: Rick Edgecombe <rick.p.edgecombe@intel.com>
> ---
>  - Drop the misleading "defined for consistency" line. It's a copy-paste
>    error introduced in the earlier patches. Earlier there was padding at
>    the end to match struct kvm_sev_cmd size. (Tony)
> Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
> ---
>  arch/x86/include/asm/kvm-x86-ops.h |  2 +-
>  arch/x86/include/uapi/asm/kvm.h    | 23 +++++++++++++++++++++
>  arch/x86/kvm/vmx/main.c            | 10 ++++++++++
>  arch/x86/kvm/vmx/tdx.c             | 32 ++++++++++++++++++++++++++++++
>  arch/x86/kvm/vmx/x86_ops.h         |  6 ++++++
>  arch/x86/kvm/x86.c                 |  4 ----
>  6 files changed, 72 insertions(+), 5 deletions(-)
> 
> diff --git a/arch/x86/include/asm/kvm-x86-ops.h b/arch/x86/include/asm/kvm-x86-ops.h
> index 823c0434bbad..1eca04087cf4 100644
> --- a/arch/x86/include/asm/kvm-x86-ops.h
> +++ b/arch/x86/include/asm/kvm-x86-ops.h
> @@ -125,7 +125,7 @@ KVM_X86_OP(leave_smm)
>  KVM_X86_OP(enable_smi_window)
>  #endif
>  KVM_X86_OP_OPTIONAL(dev_get_attr)
> -KVM_X86_OP_OPTIONAL(mem_enc_ioctl)
> +KVM_X86_OP(mem_enc_ioctl)
>  KVM_X86_OP_OPTIONAL(mem_enc_register_region)
>  KVM_X86_OP_OPTIONAL(mem_enc_unregister_region)
>  KVM_X86_OP_OPTIONAL(vm_copy_enc_context_from)
> diff --git a/arch/x86/include/uapi/asm/kvm.h b/arch/x86/include/uapi/asm/kvm.h
> index 9e75da97bce0..2b0317b47e47 100644
> --- a/arch/x86/include/uapi/asm/kvm.h
> +++ b/arch/x86/include/uapi/asm/kvm.h
> @@ -927,4 +927,27 @@ struct kvm_hyperv_eventfd {
>  #define KVM_X86_SNP_VM		4
>  #define KVM_X86_TDX_VM		5
>  
> +/* Trust Domain eXtension sub-ioctl() commands. */

(came from reviewing the KVM TDX documentation patch)

Nitpickings:

eXtension -> Extensions, since the latter is used widely in other places (and
already used in the upstream kernel).

'sub-command(s)' is used in the changelog, and in below as well.  For
consistency I think we can change 'sub-ioctl() commands' to 'sub-commands'.

> +enum kvm_tdx_cmd_id {
> +	KVM_TDX_CMD_NR_MAX,
> +};
> +
> +struct kvm_tdx_cmd {
> +	/* enum kvm_tdx_cmd_id */
> +	__u32 id;
> +	/* flags for sub-commend. If sub-command doesn't use this, set zero. */
		     ^
		     sub-command.

> +	__u32 flags;
> +	/*
> +	 * data for each sub-command. An immediate or a pointer to the actual
> +	 * data in process virtual address.  If sub-command doesn't use it,
> +	 * set zero.
> +	 */
> +	__u64 data;
> +	/*
> +	 * Auxiliary error code.  The sub-command may return TDX SEAMCALL
> +	 * status code in addition to -Exxx.
> +	 */
> +	__u64 hw_error;
> +};