Cherry-pick Preserve guest XSAVE state across userland transitions (#1537) to ulitebox

Cargo.toml

@@ -2,6 +2,7 @@
 resolver = "2"
 members = [
     "litebox",
+    "litebox_common",
     "litebox_broker_local",
     "litebox_broker_local_userland",
     "litebox_broker_core",
@@ -60,6 +61,7 @@ members = [
 ]
 default-members = [
     "litebox",
+    "litebox_common",
     "litebox_broker_local",
     "litebox_broker_local_userland",
     "litebox_broker_core",

dev_tests/src/ratchet.rs

@@ -72,15 +72,16 @@ fn ratchet_globals() -> Result<()> {
             ("litebox_broker_core/", 1),
             ("litebox_broker_transport_linux_userland/", 1),
             ("litebox_broker_userland/", 1),
+            ("litebox_common/", 1),
             ("litebox_hal/", 1),
             ("litebox_platform/", 2),
             ("litebox_platform_linux_kernel/", 5),
-            ("litebox_platform_linux_userland/", 6),
+            ("litebox_platform_linux_userland/", 7),
             ("litebox_platform_macos_userland/", 7),
             ("litebox_platform_lvbs/", 23),
             ("litebox_platform_vm_kernel/", 4),
             ("litebox_platform_vm_userland/", 1),
-            ("litebox_platform_windows_userland/", 11),
+            ("litebox_platform_windows_userland/", 10),
             ("litebox_runner_lvbs/", 8),
             ("litebox_runner_optee_on_qemu/", 1),
             ("litebox_runner_optee_on_vm_userland/", 1),

litebox/src/platform/vector.rs

@@ -18,7 +18,7 @@ pub trait GuestVectorStateProvider {
 
 // TODO: replace this blanket with architecture-specific providers before
 // implementing guest vector-state preservation outside AArch64.
-#[cfg(not(target_arch = "aarch64"))]
+#[cfg(not(any(target_arch = "aarch64", target_arch = "x86_64")))]
 impl<T> GuestVectorStateProvider for T {
     type GuestVectorState = ();
 

litebox_common/Cargo.toml

@@ -0,0 +1,13 @@
+[package]
+name = "litebox_common"
+version = "0.1.0"
+edition = "2024"
+license = "MIT"
+repository = "https://github.com/microsoft/litebox"
+description = "Common definitions shared across LiteBox shims and platforms"
+
+[dependencies]
+spin = { version = "0.9.8", default-features = false, features = ["once"] }
+
+[lints]
+workspace = true

litebox_common/src/arch/mod.rs

@@ -0,0 +1,7 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+//! Architecture-specific helpers independent of host operating systems and guest ABIs.
+
+#[cfg(target_arch = "x86_64")]
+pub mod x86_64;

litebox_common/src/arch/x86_64/mod.rs

@@ -0,0 +1,6 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT license.
+
+//! Shared x86-64 CPU-state helpers.
+
+pub mod xstate;