vmm, virtio-devices: mem: Don't use MADV_DONTNEED on hugepages

This commit introduces a new information to the VirtioMemZone structure
in order to know if the memory zone is backed by hugepages.

Based on this new information, the virtio-mem device is now able to
determine if madvise(MADV_DONTNEED) should be performed or not. The
madvise documentation specifies that MADV_DONTNEED advice will fail if
the memory range has been allocated with some hugepages.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
Signed-off-by: Hui Zhu <teawater@antfin.com>

vmm/src/memory_manager.rs

@@ -72,6 +72,7 @@ pub struct VirtioMemZone {
     region: Arc<GuestRegionMmap>,
     resize_handler: virtio_devices::Resize,
     hotplugged_size: u64,
+    hugepages: bool,
 }
 
 impl VirtioMemZone {
@@ -84,6 +85,9 @@ impl VirtioMemZone {
     pub fn hotplugged_size(&self) -> u64 {
         self.hotplugged_size
     }
+    pub fn hugepages(&self) -> bool {
+        self.hugepages
+    }
 }
 
 #[derive(Default)]
@@ -684,6 +688,7 @@ impl MemoryManager {
                             resize_handler: virtio_devices::Resize::new()
                                 .map_err(Error::EventFdFail)?,
                             hotplugged_size: zone.hotplugged_size.unwrap_or(0),
+                            hugepages: zone.hugepages,
                         });
 
                         start_of_device_area = start_addr