vmm: memory_manager: Extract code for allocating new memory

This function can then be used by the TDX code to allocate the memory at
specific locations required for the TDVF to run from.

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

vmm/src/memory_manager.rs

@@ -1093,25 +1093,11 @@ impl MemoryManager {
         Ok(start_addr)
     }
 
-    fn hotplug_ram_region(&mut self, size: usize) -> Result<Arc<GuestRegionMmap>, Error> {
+    pub fn add_ram_region(
-        info!("Hotplugging new RAM: {}", size);
+        &mut self,
-
+        start_addr: GuestAddress,
-        // Check that there is a free slot
+        size: usize,
-        if self.next_hotplug_slot >= HOTPLUG_COUNT {
+    ) -> Result<Arc<GuestRegionMmap>, Error> {
-            return Err(Error::NoSlotAvailable);
-        }
-
-        // "Inserted" DIMM must have a size that is a multiple of 128MiB
-        if size % (128 << 20) != 0 {
-            return Err(Error::InvalidSize);
-        }
-
-        let start_addr = MemoryManager::start_addr(self.guest_memory.memory().last_addr(), true)?;
-
-        if start_addr.checked_add(size.try_into().unwrap()).unwrap() > self.start_of_device_area() {
-            return Err(Error::InsufficientHotplugRAM);
-        }
-
         // Allocate memory for the region
         let region = MemoryManager::create_ram_region(
             &None,
@@ -1140,6 +1126,32 @@ impl MemoryManager {
             slot,
         });
 
+        self.add_region(Arc::clone(&region))?;
+
+        Ok(region)
+    }
+
+    fn hotplug_ram_region(&mut self, size: usize) -> Result<Arc<GuestRegionMmap>, Error> {
+        info!("Hotplugging new RAM: {}", size);
+
+        // Check that there is a free slot
+        if self.next_hotplug_slot >= HOTPLUG_COUNT {
+            return Err(Error::NoSlotAvailable);
+        }
+
+        // "Inserted" DIMM must have a size that is a multiple of 128MiB
+        if size % (128 << 20) != 0 {
+            return Err(Error::InvalidSize);
+        }
+
+        let start_addr = MemoryManager::start_addr(self.guest_memory.memory().last_addr(), true)?;
+
+        if start_addr.checked_add(size.try_into().unwrap()).unwrap() > self.start_of_device_area() {
+            return Err(Error::InsufficientHotplugRAM);
+        }
+
+        let region = self.add_ram_region(start_addr, size)?;
+
         // Tell the allocator
         self.allocator
             .lock()
@@ -1156,8 +1168,6 @@ impl MemoryManager {
 
         self.next_hotplug_slot += 1;
 
-        self.add_region(Arc::clone(&region))?;
-
         Ok(region)
     }