From 94fcfa9f1f43e635c6a610e30c1b2932a2fb562f Mon Sep 17 00:00:00 2001
From: Wei Liu <liuwe@microsoft.com>
Date: Wed, 17 Nov 2021 13:43:00 +0000
Subject: [PATCH] virtio-queue: add safety comments for `impl ByteValued`

Signed-off-by: Wei Liu <liuwe@microsoft.com>
---
 virtio-queue/src/lib.rs | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/virtio-queue/src/lib.rs b/virtio-queue/src/lib.rs
index d321f6f3e..353901439 100644
--- a/virtio-queue/src/lib.rs
+++ b/virtio-queue/src/lib.rs
@@ -94,6 +94,9 @@ pub struct Descriptor {
     next: u16,
 }
 
+// SAFETY: Descriptor only contains a series of integers and has no implicit padding
+unsafe impl ByteValued for Descriptor {}
+
 #[allow(clippy::len_without_is_empty)]
 impl Descriptor {
     /// Creates a new descriptor
@@ -149,8 +152,6 @@ impl Descriptor {
     }
 }
 
-unsafe impl ByteValued for Descriptor {}
-
 /// A virtio descriptor chain.
 #[derive(Clone, Debug)]
 pub struct DescriptorChain<M: GuestAddressSpace> {
@@ -421,6 +422,9 @@ pub struct VirtqUsedElem {
     len: u32,
 }
 
+// SAFETY: VirtqUsedElem only contains a series of integers and has no implicit padding
+unsafe impl ByteValued for VirtqUsedElem {}
+
 impl VirtqUsedElem {
     /// Create a new `VirtqUsedElem` instance.
     pub fn new(id: u16, len: u32) -> Self {
@@ -431,8 +435,6 @@ impl VirtqUsedElem {
     }
 }
 
-unsafe impl ByteValued for VirtqUsedElem {}
-
 /// Struct to hold an exclusive reference to the underlying `QueueState` object.
 pub enum QueueStateGuard<'a, M: GuestAddressSpace> {
     /// A reference to a `QueueState` object.