test(uffd_utils): add protocol definitions for secret freedom

This is needed because if guest_memfd is used to back guest memory, vCPU
fault notifications are delivered via the UFFD UDS socket.

Signed-off-by: Nikita Kalyazin <[email protected]>

Author: kalyazin

src/firecracker/examples/uffd/uffd_utils.rs

@@ -34,6 +34,68 @@ pub struct GuestRegionUffdMapping {
     pub offset: u64,
     /// The configured page size for this memory region.
     pub page_size: usize,
+    #[deprecated]
+    pub page_size_kib: usize,
+}
+
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]
+pub struct FaultRequest {
+    /// vCPU that encountered the fault (not meaningful to Fission)
+    pub vcpu: u32,
+    /// Offset in guest_memfd where the fault occured
+    pub offset: u64,
+    /// Flags (not meaningful to Fission)
+    pub flags: u64,
+    /// Async PF token (not meaningful to Fission)
+    pub token: Option<u32>,
+}
+
+impl FaultRequest {
+    pub fn into_reply(self, len: u64) -> FaultReply {
+        FaultReply {
+            vcpu: Some(self.vcpu),
+            offset: self.offset,
+            len,
+            flags: self.flags,
+            token: self.token,
+            zero: false,
+        }
+    }
+}
+
+/// FaultReply
+#[derive(Clone, Debug, Serialize, Deserialize, PartialEq, Eq)]
+pub struct FaultReply {
+    /// vCPU that encountered the fault, from `FaultRequest` (if present, otherwise 0)
+    pub vcpu: Option<u32>,
+    /// Offset in guest_memfd where population started
+    pub offset: u64,
+    /// Length of populated area
+    pub len: u64,
+    /// Flags, must be copied from `FaultRequest`, otherwise 0
+    pub flags: u64,
+    /// Async PF token, must be copied from `FaultRequest`, otherwise None
+    pub token: Option<u32>,
+    /// Whether the populated pages are zero pages
+    pub zero: bool,
+}
+
+/// UffdMsgFromFirecracker
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(untagged)]
+pub enum UffdMsgFromFirecracker {
+    /// Mappings
+    Mappings(Vec<GuestRegionUffdMapping>),
+    /// FaultReq
+    FaultReq(FaultRequest),
+}
+
+/// UffdMsgToFirecracker
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(untagged)]
+pub enum UffdMsgToFirecracker {
+    /// FaultRep
+    FaultRep(FaultReply),
 }
 
 impl GuestRegionUffdMapping {