tdx: Add "tdx" feature with an empty module inside arch to implement

Add the skeleton of the "tdx" feature with a module ready inside the
arch crate to store implementation details.

TEST=cargo build --features="tdx"

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

Cargo.toml

@@ -56,6 +56,7 @@ fwdebug = ["vmm/fwdebug"]
 kvm = ["vmm/kvm"]
 mshv = ["vmm/mshv"]
 io_uring = ["vmm/io_uring"]
+tdx = ["vmm/tdx"]
 
 # Integration tests require a special environment to run in
 integration_tests = []

arch/Cargo.toml

@@ -6,6 +6,7 @@ authors = ["The Chromium OS Authors"]
 [features]
 default = []
 acpi = ["acpi_tables"]
+tdx = []
 
 [dependencies]
 acpi_tables = { path = "../acpi_tables", optional = true }

arch/src/x86_64/mod.rs

@@ -25,6 +25,8 @@ use vm_memory::{
 };
 mod smbios;
 use std::arch::x86_64;
+#[cfg(feature = "tdx")]
+pub mod tdx;
 
 #[derive(Debug, Copy, Clone)]
 pub enum BootProtocol {

arch/src/x86_64/tdx/mod.rs

@@ -0,0 +1,4 @@
+// Copyright © 2021 Intel Corporation
+//
+// SPDX-License-Identifier: Apache-2.0
+

vmm/Cargo.toml

@@ -12,6 +12,7 @@ fwdebug = ["devices/fwdebug"]
 kvm = ["hypervisor/kvm"]
 mshv = ["hypervisor/mshv"]
 io_uring = ["virtio-devices/io_uring"]
+tdx = ["arch/tdx"]
 
 [dependencies]
 acpi_tables = { path = "../acpi_tables", optional = true }