feat(mem): introduce KVM slots per GuestMemoryRegion

A single GuestMemoryRegion can be split into multiple KVM slots. This is
used for Hotplug type regions where we can dynamically remove access to
the region from the guest.

Signed-off-by: Riccardo Mancini <[email protected]>

Author: Manciukic

src/vmm/src/builder.rs

@@ -180,7 +180,10 @@ pub fn build_microvm_for_boot(
         let hotplug_memory_region = vm_resources
             .allocate_memory_region(addr, mib_to_bytes(memory_hotplug.total_size_mib))
             .map_err(StartMicrovmError::GuestMemory)?;
-        vm.register_hotpluggable_memory_region(hotplug_memory_region)?;
+        vm.register_hotpluggable_memory_region(
+            hotplug_memory_region,
+            mib_to_bytes(memory_hotplug.slot_size_mib),
+        )?;
         Some(addr)
     } else {
         None

src/vmm/src/devices/virtio/mem/device.rs

@@ -692,6 +692,7 @@ pub(crate) mod test_utils {
             .unwrap()
             .pop()
             .unwrap(),
+            mib_to_bytes(128),
         );
         let vm = Arc::new(vm);
         VirtioMem::new(vm, addr, 1024, 2, 128).unwrap()

src/vmm/src/persist.rs

@@ -571,6 +571,7 @@ fn send_uffd_handshake(
 mod tests {
     use std::os::unix::net::UnixListener;
 
+    use bitvec::vec::BitVec;
     use vmm_sys_util::tempfile::TempFile;
 
     use super::*;
@@ -698,6 +699,7 @@ mod tests {
                 base_address: 0,
                 size: 0x20000,
                 region_type: GuestRegionType::Dram,
+                plugged: BitVec::repeat(true, 1),
             }],
         };