runtime-rs: Add reclaim_guest_freed_memory cloud-hypervisor support

Add reclaim_guest_freed_memory config to cloud-hypervisor in runtime-rs.

Fixes: #10710

Signed-off-by: Hui Zhu <teawater@antgroup.com>

src/runtime-rs/config/configuration-cloud-hypervisor.toml.in

@@ -158,6 +158,16 @@ virtio_fs_cache = "@DEFVIRTIOFSCACHE@"
 # > 5                --> will be set to 5
 default_bridges = @DEFBRIDGES@
 
+# Reclaim guest freed memory.
+# Enabling this will result in the VM balloon device having f_reporting=on set.
+# Then the hypervisor will use it to reclaim guest freed memory.
+# This is useful for reducing the amount of memory used by a VM.
+# Enabling this feature may sometimes reduce the speed of memory access in
+# the VM.
+#
+# Default false
+#reclaim_guest_freed_memory = true
+
 # Block storage driver to be used for the hypervisor in case the container
 # rootfs is backed by a block device.
 block_device_driver = "virtio-blk-pci"

src/runtime-rs/crates/hypervisor/ch-config/src/convert.rs

@@ -180,6 +180,15 @@ impl TryFrom<NamedHypervisorConfig> for VmConfig {
 
         let platform = get_platform_cfg(guest_protection_to_use);
 
+        let balloon = if cfg.device_info.reclaim_guest_freed_memory {
+            Some(crate::BalloonConfig {
+                free_page_reporting: true,
+                ..Default::default()
+            })
+        } else {
+            None
+        };
+
         let cfg = VmConfig {
             cpus,
             memory,
@@ -193,6 +202,7 @@ impl TryFrom<NamedHypervisorConfig> for VmConfig {
             vsock: Some(vsock),
             rng,
             platform,
+            balloon,
 
             ..Default::default()
         };