vmm: config: Validate balloon size is less than RAM size

Signed-off-by: Rob Bradford <robert.bradford@intel.com>

vmm/src/config.rs

@@ -155,6 +155,8 @@ pub enum ValidationError {
     InvalidNumPciSegments(u16),
     /// Invalid PCI segment id
     InvalidPciSegment(u16),
+    /// Balloon too big
+    BalloonLargerThanRam(u64, u64),
 }
 
 type ValidationResult<T> = std::result::Result<T, ValidationError>;
@@ -218,6 +220,13 @@ impl fmt::Display for ValidationError {
             InvalidPciSegment(pci_segment) => {
                 write!(f, "Invalid PCI segment id{}", pci_segment)
             }
+            BalloonLargerThanRam(balloon_size, ram_size) => {
+                write!(
+                    f,
+                    "Ballon size ({}) greater than RAM ({})",
+                    balloon_size, ram_size
+                )
+            }
         }
     }
 }
@@ -2165,6 +2174,23 @@ impl VmConfig {
             }
         }
 
+        if let Some(balloon) = &self.balloon {
+            let mut ram_size = self.memory.size;
+
+            if let Some(zones) = &self.memory.zones {
+                for zone in zones {
+                    ram_size += zone.size;
+                }
+            }
+
+            if balloon.size >= ram_size {
+                return Err(ValidationError::BalloonLargerThanRam(
+                    balloon.size,
+                    ram_size,
+                ));
+            }
+        }
+
         if let Some(devices) = &self.devices {
             for device in devices {
                 device.validate(self)?;