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SubjectRe: [RFC PATCH v5 025/104] KVM: TDX: Add place holder for TDX VM specific mem_enc_op ioctl
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On 3/4/22 20:48, isaku.yamahata@intel.com wrote:
> From: Isaku Yamahata <isaku.yamahata@intel.com>
>
> 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@intel.com>
> ---
> 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

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