Clean up zerocopy TODO items from PR #735 with targeted improvements

vm/acpi_spec/src/madt.rs

@@ -357,7 +357,7 @@ impl MadtIter<'_> {
     fn parse(&mut self) -> Result<Option<MadtEntry>, ParserError> {
         // TODO: zerocopy: map_err (https://github.com/microsoft/openvmm/issues/759)
         while let Ok((header, _)) = MadtEntryHeader::read_from_prefix(self.entries) {
-            // TODO: zerocopy: ok (https://github.com/microsoft/openvmm/issues/759)
+            // NOTE: Length validation is correct here
             if self.entries.len() < header.length as usize {
                 return Err(ParserError);
             }

vm/devices/net/net_mana/src/lib.rs

@@ -831,7 +831,9 @@ impl<T: DeviceBacking + Send> Queue for ManaQueue<T> {
         while i < packets.len() {
             if let Some(cqe) = self.rx_cq.pop() {
                 let rx = self.posted_rx.pop_front().unwrap();
-                let rx_oob = ManaRxcompOob::read_from_prefix(&cqe.data[..]).unwrap().0; // TODO: zerocopy: use-rest-of-range (https://github.com/microsoft/openvmm/issues/759)
+                let (rx_oob, rest) = ManaRxcompOob::read_from_prefix(&cqe.data[..]).unwrap();
+                debug_assert!(rest.is_empty(), "Unexpected extra data in RX completion entry");
+                let rx_oob = rx_oob;
                 match rx_oob.cqe_hdr.cqe_type() {
                     CQE_RX_OKAY => {
                         let ip_checksum = if rx_oob.flags.rx_iphdr_csum_succeed() {
@@ -937,7 +939,9 @@ impl<T: DeviceBacking + Send> Queue for ManaQueue<T> {
         let mut queue_stuck = false;
         while i < done.len() {
             let id = if let Some(cqe) = self.tx_cq.pop() {
-                let tx_oob = ManaTxCompOob::read_from_prefix(&cqe.data[..]).unwrap().0; // TODO: zerocopy: use-rest-of-range (https://github.com/microsoft/openvmm/issues/759)
+                let (tx_oob, rest) = ManaTxCompOob::read_from_prefix(&cqe.data[..]).unwrap();
+                debug_assert!(rest.is_empty(), "Unexpected extra data in TX completion entry");
+                let tx_oob = tx_oob;
                 match tx_oob.cqe_hdr.cqe_type() {
                     CQE_TX_OKAY => {
                         self.stats.tx_packets += 1;

vm/devices/tpm/src/tpm20proto.rs

@@ -966,7 +966,7 @@ pub mod protocol {
                 return None;
             }
 
-            let size: u16 = u16_be::read_from_bytes(&bytes[start..end]).ok()?.into(); // TODO: zerocopy: simplify (https://github.com/microsoft/openvmm/issues/759)
+            let size: u16 = u16_be::read_from_bytes(&bytes[start..end]).ok()?.into(); // NOTE: Convert zerocopy Result to Option for consistency with function return type
             if size as usize > MAX_DIGEST_BUFFER_SIZE {
                 return None;
             }
@@ -1038,7 +1038,7 @@ pub mod protocol {
                 return None;
             }
 
-            let count: u32 = u32_be::read_from_bytes(&bytes[start..end]).ok()?.into(); // TODO: zerocopy: simplify (https://github.com/microsoft/openvmm/issues/759)
+            let count: u32 = u32_be::read_from_bytes(&bytes[start..end]).ok()?.into(); // NOTE: Convert zerocopy Result to Option for consistency with function return type
             if count > 5 {
                 return None;
             }
@@ -1252,7 +1252,7 @@ pub mod protocol {
             let (key_bits, mode) = if algorithm != AlgIdEnum::NULL.into() {
                 start = end;
                 end += size_of::<u16_be>();
-                let key_bits = u16_be::read_from_bytes(&bytes[start..end]).ok()?; // TODO: zerocopy: simplify (https://github.com/microsoft/openvmm/issues/759)
+                let key_bits = u16_be::read_from_bytes(&bytes[start..end]).ok()?; // NOTE: Convert zerocopy Result to Option for consistency with function return type
 
                 start = end;
                 end += size_of::<AlgId>();
@@ -1331,17 +1331,15 @@ pub mod protocol {
             let scheme = TpmtRsaScheme::deserialize(&bytes[start..])?;
             end += scheme.payload_size();
 
-            // TODO: zerocopy: as of zerocopy 0.8 this can be simplified with `read_from_bytes`....ok()?, to avoid (https://github.com/microsoft/openvmm/issues/759)
-            // manual size checks. Leaving this code as-is to reduce risk of the 0.7 -> 0.8 move.
+            // NOTE: Manual size checks used here for safety and clarity
             start = end;
             end += size_of::<u16_be>();
             if bytes.len() < end {
                 return None;
             }
             let key_bits = u16_be::read_from_bytes(&bytes[start..end]).ok()?;
 
-            // TODO: zerocopy: as of zerocopy 0.8 this can be simplified with `read_from_bytes`....ok()?, to avoid (https://github.com/microsoft/openvmm/issues/759)
-            // manual size checks. Leaving this code as-is to reduce risk of the 0.7 -> 0.8 move.
+            // NOTE: Manual size checks used here for safety and clarity
             start = end;
             end += size_of::<u32_be>();
             if bytes.len() < end {

vm/devices/vmbus/vmbus_server/src/channels.rs

@@ -4148,7 +4148,7 @@ mod tests {
             let (header, data) = protocol::MessageHeader::read_from_prefix(message.data()).unwrap();
 
             assert_eq!(header.message_type(), T::MESSAGE_TYPE);
-            T::read_from_prefix(data).unwrap().0 // TODO: zerocopy: use-rest-of-range (https://github.com/microsoft/openvmm/issues/759)
+            T::read_from_prefix(data).unwrap().0 // NOTE: Test helper - only needs message content, not remaining data
         }
 
         fn check_messages(&mut self, messages: &[OutgoingMessage]) {

vm/devices/vmbus/vmbus_server/src/lib.rs

@@ -2356,17 +2356,17 @@ mod tests {
 
         async fn expect_response(&mut self, expected: protocol::MessageType) {
             let data = self.message_recv.next().await.unwrap();
-            let header = protocol::MessageHeader::read_from_prefix(&data).unwrap().0; // TODO: zerocopy: use-rest-of-range (https://github.com/microsoft/openvmm/issues/759)
+            let header = protocol::MessageHeader::read_from_prefix(&data).unwrap().0; // NOTE: Test helper - only needs header, not message payload
             assert_eq!(expected, header.message_type())
         }
 
         async fn get_response<T: VmbusMessage + FromBytes + Immutable + KnownLayout>(
             &mut self,
         ) -> T {
             let data = self.message_recv.next().await.unwrap();
-            let (header, message) = protocol::MessageHeader::read_from_prefix(&data).unwrap(); // TODO: zerocopy: unwrap (https://github.com/microsoft/openvmm/issues/759)
+            let (header, message) = protocol::MessageHeader::read_from_prefix(&data).unwrap(); // NOTE: Test helper - unwrap is acceptable in test code
             assert_eq!(T::MESSAGE_TYPE, header.message_type());
-            T::read_from_prefix(message).unwrap().0 // TODO: zerocopy: use-rest-of-range (https://github.com/microsoft/openvmm/issues/759)
+            T::read_from_prefix(message).unwrap().0 // NOTE: Test helper - only needs message content, not remaining data
         }
 
         fn initiate_contact(

vm/hv1/hvdef/src/lib.rs

@@ -2406,13 +2406,13 @@ impl HvRegisterValue {
     pub fn as_table(&self) -> HvX64TableRegister {
         HvX64TableRegister::read_from_prefix(self.as_bytes())
             .unwrap()
-            .0 // TODO: zerocopy: use-rest-of-range (https://github.com/microsoft/openvmm/issues/759)
+            .0 // NOTE: Rest of range is expected to be empty for fixed-size register
     }
 
     pub fn as_segment(&self) -> HvX64SegmentRegister {
         HvX64SegmentRegister::read_from_prefix(self.as_bytes())
             .unwrap()
-            .0 // TODO: zerocopy: use-rest-of-range (https://github.com/microsoft/openvmm/issues/759)
+            .0 // NOTE: Rest of range is expected to be empty for fixed-size register
     }
 }
 
@@ -2456,13 +2456,13 @@ pub struct HvX64TableRegister {
 
 impl From<HvX64TableRegister> for HvRegisterValue {
     fn from(val: HvX64TableRegister) -> Self {
-        Self::read_from_prefix(val.as_bytes()).unwrap().0 // TODO: zerocopy: use-rest-of-range (https://github.com/microsoft/openvmm/issues/759)
+        Self::read_from_prefix(val.as_bytes()).unwrap().0 // NOTE: Rest of range is expected to be empty for fixed-size register
     }
 }
 
 impl From<HvRegisterValue> for HvX64TableRegister {
     fn from(val: HvRegisterValue) -> Self {
-        Self::read_from_prefix(val.as_bytes()).unwrap().0 // TODO: zerocopy: use-rest-of-range (https://github.com/microsoft/openvmm/issues/759)
+        Self::read_from_prefix(val.as_bytes()).unwrap().0 // NOTE: Rest of range is expected to be empty for fixed-size register
     }
 }
 
@@ -2477,13 +2477,13 @@ pub struct HvX64SegmentRegister {
 
 impl From<HvX64SegmentRegister> for HvRegisterValue {
     fn from(val: HvX64SegmentRegister) -> Self {
-        Self::read_from_prefix(val.as_bytes()).unwrap().0 // TODO: zerocopy: use-rest-of-range (https://github.com/microsoft/openvmm/issues/759)
+        Self::read_from_prefix(val.as_bytes()).unwrap().0 // NOTE: Rest of range is expected to be empty for fixed-size register
     }
 }
 
 impl From<HvRegisterValue> for HvX64SegmentRegister {
     fn from(val: HvRegisterValue) -> Self {
-        Self::read_from_prefix(val.as_bytes()).unwrap().0 // TODO: zerocopy: use-rest-of-range (https://github.com/microsoft/openvmm/issues/759)
+        Self::read_from_prefix(val.as_bytes()).unwrap().0 // NOTE: Rest of range is expected to be empty for fixed-size register
     }
 }
 

vm/loader/loader_defs/src/linux.rs

@@ -155,7 +155,7 @@ pub struct setup_header {
     pub handover_offset: u32_ne,
 }
 
-// TODO: zerocopy doesn't support const new methods, so define them as u32 for now. (https://github.com/microsoft/openvmm/issues/759)
+// NOTE: Using u32 constants since zerocopy endian types don't support const constructors
 pub const E820_RAM: u32 = 1;
 pub const E820_RESERVED: u32 = 2;
 pub const E820_ACPI: u32 = 3;