vmm: Allow receiving information about changing MemoryZones

It is possible to migrate a VM to a host that might have a different
but compatible NUMA configuration. For example, it should be possible
to move a `MemoryZone` from NUMA node 2 and 3 of the sender to nodes
0 and 1 on the receiver, given sender and receiver nodes are compatible
with respect to available memory.

In such a case, we need to adjust the mapping of guest memory to host
nodes. We need this information for live migration as well as for
snapshot (when performing cold migration). We consume this information
in the following commit.

Signed-off-by: Pascal Scholz <pascal.scholz@cyberus-technology.de>
On-behalf-of: SAP pascal.scholz@sap.com

vmm/src/api/mod.rs

@@ -54,7 +54,9 @@ use vmm_sys_util::eventfd::EventFd;
 pub use self::dbus::start_dbus_thread;
 pub use self::http::{start_http_fd_thread, start_http_path_thread};
 use crate::Error as VmmError;
-use crate::config::{RestoreConfig, RestoredVfioConfig, deserialize_restored_fd};
+use crate::config::{
+    RestoreConfig, RestoredVfioConfig, VmMemoryZoneUpdateData, deserialize_restored_fd,
+};
 use crate::device_tree::DeviceTree;
 use crate::migration::transport::{
     MAX_MIGRATION_CONNECTIONS, TcpAddressParseError, tcp_address_to_server_name,
@@ -319,6 +321,9 @@ pub struct VmReceiveMigrationData {
     // FDs are not serialized and any deserialized value is invalid; see NetConfig::fds.
     #[serde(default, deserialize_with = "deserialize_restored_fd")]
     pub iommufd_fd: Option<i32>,
+    /// Optional memory zone update data
+    #[serde(default)]
+    pub zone_updates: Vec<VmMemoryZoneUpdateData>,
 }
 
 #[derive(Debug, Error)]
@@ -381,6 +386,7 @@ impl VmReceiveMigrationData {
             memory_mode,
             vfio_fds,
             iommufd_fd,
+            zone_updates: vec![],
         };
 
         data.validate()?;
@@ -2089,6 +2095,7 @@ mod unit_tests {
                 memory_mode: MigrationMode::Precopy,
                 vfio_fds: None,
                 iommufd_fd: None,
+                zone_updates: vec![],
             }
         );
 
@@ -2118,6 +2125,7 @@ mod unit_tests {
                 memory_mode: MigrationMode::Precopy,
                 vfio_fds: None,
                 iommufd_fd: None,
+                zone_updates: vec![],
             }
         );
 
@@ -2143,6 +2151,7 @@ mod unit_tests {
                 memory_mode: MigrationMode::Precopy,
                 vfio_fds: None,
                 iommufd_fd: None,
+                ..Default::default()
             }
         );
 
@@ -2158,6 +2167,7 @@ mod unit_tests {
                 memory_mode: MigrationMode::Postcopy,
                 vfio_fds: None,
                 iommufd_fd: None,
+                ..Default::default()
             }
         );