From 1e1a50ef705d1af10972fdccdcc7341c82902845 Mon Sep 17 00:00:00 2001
From: Sebastien Boeuf <sebastien.boeuf@intel.com>
Date: Mon, 14 Sep 2020 23:50:30 +0200
Subject: [PATCH] vmm: Update memory configuration upon virtio-mem resizing

Based on all the preparatory work achieved through previous commits,
this patch updates the 'hotplugged_size' field for both MemoryConfig and
MemoryZoneConfig structures when either the whole memory is resized, or
simply when a memory zone is resized.

This fixes the lack of support for rebooting a VM with the right amount
of memory plugged in.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>
---
 vmm/src/memory_manager.rs | 31 +++-------------------
 vmm/src/vm.rs             | 55 ++++++++++++++++++++++++++++++++++-----
 2 files changed, 52 insertions(+), 34 deletions(-)

diff --git a/vmm/src/memory_manager.rs b/vmm/src/memory_manager.rs
index 95b589009..11f27dd52 100644
--- a/vmm/src/memory_manager.rs
+++ b/vmm/src/memory_manager.rs
@@ -664,8 +664,8 @@ impl MemoryManager {
             mergeable: config.mergeable,
             allocator: allocator.clone(),
             hotplug_method: config.hotplug_method.clone(),
-            boot_ram: config.size,
-            current_ram: config.size,
+            boot_ram: ram_size,
+            current_ram: ram_size,
             next_hotplug_slot: 0,
             snapshot: Mutex::new(None),
             shared: config.shared,
@@ -1268,12 +1268,7 @@ impl MemoryManager {
         Ok(region)
     }
 
-    pub fn resize_zone(
-        &mut self,
-        id: &str,
-        desired_ram: u64,
-        config: &MemoryConfig,
-    ) -> Result<(), Error> {
+    pub fn resize_zone(&mut self, id: &str, virtio_mem_size: u64) -> Result<(), Error> {
         if !self.user_provided_zones {
             error!(
                 "Not allowed to resize guest memory zone when no zone is \
@@ -1282,25 +1277,7 @@ impl MemoryManager {
             return Err(Error::ResizeZone);
         }
 
-        if let Some(zones) = &config.zones {
-            for zone in zones.iter() {
-                if zone.id == id {
-                    if desired_ram >= zone.size {
-                        return self.virtio_mem_resize(id, desired_ram - zone.size);
-                    } else {
-                        error!(
-                            "Invalid to ask less ({}) than boot RAM ({}) for \
-                            this memory zone",
-                            desired_ram, zone.size,
-                        );
-                        return Err(Error::ResizeZone);
-                    }
-                }
-            }
-        }
-
-        error!("Could not find the memory zone {} for the resize", id);
-        Err(Error::ResizeZone)
+        self.virtio_mem_resize(id, virtio_mem_size)
     }
 
     #[cfg(target_arch = "x86_64")]
diff --git a/vmm/src/vm.rs b/vmm/src/vm.rs
index 29217a196..a4f5be344 100644
--- a/vmm/src/vm.rs
+++ b/vmm/src/vm.rs
@@ -209,6 +209,9 @@ pub enum Error {
 
     /// Cannot apply seccomp filter
     ApplySeccompFilter(seccomp::Error),
+
+    /// Failed resizing a memory zone.
+    ResizeZone,
 }
 pub type Result<T> = result::Result<T, Error>;
 
@@ -884,6 +887,8 @@ impl Vm {
                 .resize(desired_memory)
                 .map_err(Error::MemoryManager)?;
 
+            let mut memory_config = &mut self.config.lock().unwrap().memory;
+
             if let Some(new_region) = &new_region {
                 self.device_manager
                     .lock()
@@ -891,7 +896,6 @@ impl Vm {
                     .update_memory(&new_region)
                     .map_err(Error::DeviceManager)?;
 
-                let memory_config = &self.config.lock().unwrap().memory;
                 match memory_config.hotplug_method {
                     HotplugMethod::Acpi => {
                         self.device_manager
@@ -907,7 +911,16 @@ impl Vm {
             // We update the VM config regardless of the actual guest resize
             // operation result (happened or not), so that if the VM reboots
             // it will be running with the last configure memory size.
-            self.config.lock().unwrap().memory.size = desired_memory;
+            match memory_config.hotplug_method {
+                HotplugMethod::Acpi => memory_config.size = desired_memory,
+                HotplugMethod::VirtioMem => {
+                    if desired_memory > memory_config.size {
+                        memory_config.hotplugged_size = Some(desired_memory - memory_config.size);
+                    } else {
+                        memory_config.hotplugged_size = None;
+                    }
+                }
+            }
         }
 
         if let Some(desired_ram_w_balloon) = desired_ram_w_balloon {
@@ -925,11 +938,39 @@ impl Vm {
     }
 
     pub fn resize_zone(&mut self, id: String, desired_memory: u64) -> Result<()> {
-        self.memory_manager
-            .lock()
-            .unwrap()
-            .resize_zone(&id, desired_memory, &self.config.lock().unwrap().memory)
-            .map_err(Error::MemoryManager)
+        let memory_config = &mut self.config.lock().unwrap().memory;
+
+        if let Some(zones) = &mut memory_config.zones {
+            for zone in zones.iter_mut() {
+                if zone.id == id {
+                    if desired_memory >= zone.size {
+                        let hotplugged_size = desired_memory - zone.size;
+                        self.memory_manager
+                            .lock()
+                            .unwrap()
+                            .resize_zone(&id, desired_memory - zone.size)
+                            .map_err(Error::MemoryManager)?;
+                        // We update the memory zone config regardless of the
+                        // actual 'resize-zone' operation result (happened or
+                        // not), so that if the VM reboots it will be running
+                        // with the last configured memory zone size.
+                        zone.hotplugged_size = Some(hotplugged_size);
+
+                        return Ok(());
+                    } else {
+                        error!(
+                            "Invalid to ask less ({}) than boot RAM ({}) for \
+                            this memory zone",
+                            desired_memory, zone.size,
+                        );
+                        return Err(Error::ResizeZone);
+                    }
+                }
+            }
+        }
+
+        error!("Could not find the memory zone {} for the resize", id);
+        Err(Error::ResizeZone)
     }
 
     #[cfg(not(feature = "pci_support"))]