hypervisor: Make (de)serialize for XsaveState backward compatible

Signed-off-by: Bo Chen <chen.bo@intel.com>

hypervisor/src/arch/x86/mod.rs

@@ -312,10 +312,10 @@ pub struct MsrEntry {
     pub data: u64,
 }
 
+#[repr(C)]
 #[serde_with::serde_as]
-#[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
+#[derive(Debug, Clone)]
 pub struct XsaveState {
-    #[serde_as(as = "[_; 1024usize]")]
     pub region: [u32; 1024usize],
 }
 
@@ -325,3 +325,26 @@ impl Default for XsaveState {
         unsafe { ::std::mem::zeroed() }
     }
 }
+
+impl<'de> serde::Deserialize<'de> for XsaveState {
+    fn deserialize<D>(deserializer: D) -> std::result::Result<Self, D::Error>
+    where
+        D: serde::Deserializer<'de>,
+    {
+        let region: Vec<u32> = Vec::deserialize(deserializer)?;
+        let mut val: XsaveState = XsaveState::default();
+        // This panics if the source and destination have different lengths.
+        val.region.copy_from_slice(&region[..]);
+        Ok(val)
+    }
+}
+
+impl serde::Serialize for XsaveState {
+    fn serialize<S>(&self, serializer: S) -> std::result::Result<S::Ok, S::Error>
+    where
+        S: serde::Serializer,
+    {
+        let region = &self.region[..];
+        region.serialize(serializer)
+    }
+}