vmm: Add 'hotplug_size' to memory zones

In anticipation for resizing support of an individual memory zone,
this commit introduces a new option 'hotplug_size' to '--memory-zone'
parameter. This defines the amount of memory that can be added through
each specific memory zone.

Because memory zone resize is tied to virtio-mem, make sure the user
selects 'virtio-mem' hotplug method, otherwise return an error.

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

vmm/src/memory_manager.rs

@@ -215,6 +215,9 @@ pub enum Error {
 
     /// Invalid size for resizing. Can be anything except 0.
     InvalidHotplugSize,
+
+    /// Invalid hotplug method associated with memory zones resizing capability.
+    InvalidHotplugMethodWithMemoryZones,
 }
 
 const ENABLE_FLAG: usize = 0;
@@ -442,6 +445,7 @@ impl MemoryManager {
                 shared: config.shared,
                 hugepages: config.hugepages,
                 host_numa_node: None,
+                hotplug_size: config.hotplug_size,
             }];
 
             (config.size, zones)
@@ -472,6 +476,11 @@ impl MemoryManager {
                     );
                     return Err(Error::InvalidSharedMemoryZoneWithHostNuma);
                 }
+
+                if zone.hotplug_size.is_some() && config.hotplug_method == HotplugMethod::Acpi {
+                    error!("Invalid to set ACPI hotplug method for memory zones");
+                    return Err(Error::InvalidHotplugMethodWithMemoryZones);
+                }
             }
 
             (total_ram_size, zones)