vmm: Move codebase to GuestMemoryAtomic from vm-memory

Relying on the latest vm-memory version, including the freshly
introduced structure GuestMemoryAtomic, this patch replaces every
occurrence of Arc<ArcSwap<GuestMemoryMmap> with
GuestMemoryAtomic<GuestMemoryMmap>.

The point is to rely on the common RCU-like implementation from
vm-memory so that we don't have to do it from Cloud-Hypervisor.

Fixes #735

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

vm-virtio/src/vhost_user/blk.rs

@@ -8,7 +8,6 @@ use super::Error as DeviceError;
 use super::{Error, Result};
 use crate::block::VirtioBlockConfig;
 use crate::VirtioInterrupt;
-use arc_swap::ArcSwap;
 use libc;
 use libc::EFD_NONBLOCK;
 use std::cmp;
@@ -26,7 +25,7 @@ use vhost_rs::vhost_user::{Master, VhostUserMaster, VhostUserMasterReqHandler};
 use vhost_rs::VhostBackend;
 use virtio_bindings::bindings::virtio_blk::*;
 use vm_device::{Migratable, MigratableError, Pausable, Snapshotable};
-use vm_memory::{ByteValued, GuestMemoryMmap};
+use vm_memory::{ByteValued, GuestAddressSpace, GuestMemoryAtomic, GuestMemoryMmap};
 use vmm_sys_util::eventfd::EventFd;
 
 struct SlaveReqHandler {}
@@ -219,7 +218,7 @@ impl VirtioDevice for Blk {
 
     fn activate(
         &mut self,
-        mem: Arc<ArcSwap<GuestMemoryMmap>>,
+        mem: GuestMemoryAtomic<GuestMemoryMmap>,
         interrupt_cb: Arc<dyn VirtioInterrupt>,
         queues: Vec<Queue>,
         queue_evts: Vec<EventFd>,
@@ -257,7 +256,7 @@ impl VirtioDevice for Blk {
 
         let mut vu_interrupt_list = setup_vhost_user(
             &mut self.vhost_user_blk,
-            mem.load().as_ref(),
+            &mem.memory(),
             queues,
             queue_evts,
             &interrupt_cb,