atomic: implement Clone by hand

derive(Clone) requires the GuestMemory type parameter of
GuestMemoryAtomic to be cloneable as well.  However, this
is pointless for GuestMemoryAtomic since it is basically
an Arc<> wrapper.  Make GuestMemoryAtomic<> implement Clone
always, just like Arc<>.

Signed-off-by: Paolo Bonzini <[email protected]>

Author: bonzini

CHANGELOG.md

@@ -7,6 +7,7 @@
 - \[[#311](https://github.com/rust-vmm/vm-memory/pull/311)\] Allow compiling without the ReadVolatile and WriteVolatile implementations
 - \[[#312](https://github.com/rust-vmm/vm-memory/pull/312)\] `GuestRegionContainer`, a generic container of `GuestMemoryRegion`s, generalizing `GuestMemoryMmap` (which 
   is now a type alias for `GuestRegionContainer<GuestRegionMmap>`).
+- \[[#338](https://github.com/rust-vmm/vm-memory/pull/338)\] Make `GuestMemoryAtomic` always implement `Clone`.
 
 ### Changed
 

src/atomic.rs

@@ -24,7 +24,7 @@ use crate::{GuestAddressSpace, GuestMemory};
 /// readers will not be blocked because the copies they retrieved will be collected once
 /// no one can access them anymore.  Under the assumption that updates to the memory map
 /// are rare, this allows a very efficient implementation of the `memory()` method.
-#[derive(Clone, Debug)]
+#[derive(Debug)]
 pub struct GuestMemoryAtomic<M: GuestMemory> {
     // GuestAddressSpace<M>, which we want to implement, is basically a drop-in
     // replacement for &M.  Therefore, we need to pass to devices the `GuestMemoryAtomic`
@@ -75,6 +75,14 @@ impl<M: GuestMemory> GuestMemoryAtomic<M> {
     }
 }
 
+impl<M: GuestMemory> Clone for GuestMemoryAtomic<M> {
+    fn clone(&self) -> Self {
+        Self {
+            inner: self.inner.clone(),
+        }
+    }
+}
+
 impl<M: GuestMemory> GuestAddressSpace for GuestMemoryAtomic<M> {
     type T = GuestMemoryLoadGuard<M>;
     type M = M;
@@ -196,6 +204,15 @@ mod tests {
         assert_eq!(mem3.num_regions(), 2);
         assert!(mem3.find_region(GuestAddress(0x1000)).is_some());
         assert!(mem3.find_region(GuestAddress(0x10000)).is_none());
+
+        let gm2 = gm.clone();
+        let mem4 = gm2.memory();
+        for region in mem4.iter() {
+            assert_eq!(region.len(), region_size as GuestUsize);
+        }
+        assert_eq!(mem4.num_regions(), 2);
+        assert!(mem4.find_region(GuestAddress(0x1000)).is_some());
+        assert!(mem4.find_region(GuestAddress(0x10000)).is_none());
     }
 
     #[test]