vmm: Add 'hotplugged_size' to memory parameters

Add the new option 'hotplugged_size' to both --memory-zone and --memory
parameters so that we can let the user specify a certain amount of
memory being plugged at boot.

This is also part of making sure we can store the virtio-mem size over a
reboot of the VM.

Signed-off-by: Sebastien Boeuf <sebastien.boeuf@intel.com>

docs/memory.md

@@ -17,6 +17,7 @@ struct MemoryConfig {
     hugepages: bool,
     hotplug_method: HotplugMethod,
     hotplug_size: Option<u64>,
+    hotplugged_size: Option<u64>,
     balloon: bool,
     balloon_size: u64,
     zones: Option<Vec<MemoryZoneConfig>>,
@@ -24,7 +25,7 @@ struct MemoryConfig {
 ```
 
 ```
---memory <memory>	Memory parameters "size=<guest_memory_size>,mergeable=on|off,shared=on|off,hugepages=on|off,hotplug_method=acpi|virtio-mem,hotplug_size=<hotpluggable_memory_size>,balloon=on|off"
+--memory <memory>	Memory parameters "size=<guest_memory_size>,mergeable=on|off,shared=on|off,hugepages=on|off,hotplug_method=acpi|virtio-mem,hotplug_size=<hotpluggable_memory_size>,hotplugged_size=<hotplugged_memory_size>,balloon=on|off"
 ```
 
 ### `size`
@@ -120,6 +121,27 @@ _Example_
 --memory size=1G,hotplug_size=1G
 ```
 
+### `hotplugged_size`
+
+Amount of memory that will be dynamically added to the VM at boot. This option
+allows for starting a VM with a certain amount of memory that can be reduced
+during runtime.
+
+This is only valid when the `hotplug_method` is `virtio-mem` as it does not
+make sense for the `acpi` use case. When using ACPI, the memory can't be
+resized after it has been extended.
+
+This option is only valid when `hotplug_size` is specified, and its value can't
+exceed the value of `hotplug_size`.
+
+Value is an unsigned integer of 64 bits. A value of 0 is invalid.
+
+_Example_
+
+```
+--memory size=1G,hotplug_method=virtio-mem,hotplug_size=1G,hotplugged_size=512M
+```
+
 ### `balloon`
 
 Specifies if the `virtio-balloon` device must be activated. This creates a
@@ -149,11 +171,12 @@ struct MemoryZoneConfig {
     hugepages: bool,
     host_numa_node: Option<u32>,
     hotplug_size: Option<u64>,
+    hotplugged_size: Option<u64>,
 }
 ```
 
 ```
---memory-zone <memory-zone>	User defined memory zone parameters "size=<guest_memory_region_size>,file=<backing_file>,shared=on|off,hugepages=on|off,host_numa_node=<node_id>,id=<zone_identifier>,hotplug_size=<hotpluggable_memory_size>"
+--memory-zone <memory-zone>	User defined memory zone parameters "size=<guest_memory_region_size>,file=<backing_file>,shared=on|off,hugepages=on|off,host_numa_node=<node_id>,id=<zone_identifier>,hotplug_size=<hotpluggable_memory_size>,hotplugged_size=<hotplugged_memory_size>"
 ```
 
 This parameter expects one or more occurences, allowing for a list of memory
@@ -303,6 +326,28 @@ _Example_
 --memory-zone id=mem0,size=1G,hotplug_size=1G
 ```
 
+### `hotplugged_size`
+
+Amount of memory that will be dynamically added to a memory zone at VM's boot.
+This option allows for starting a VM with a certain amount of memory that can
+be reduced during runtime.
+
+This is only valid when the `hotplug_method` is `virtio-mem` as it does not
+make sense for the `acpi` use case. When using ACPI, the memory can't be
+resized after it has been extended.
+
+This option is only valid when `hotplug_size` is specified, and its value can't
+exceed the value of `hotplug_size`.
+
+Value is an unsigned integer of 64 bits. A value of 0 is invalid.
+
+_Example_
+
+```
+--memory size=0,hotplug_method=virtio-mem
+--memory-zone id=mem0,size=1G,hotplug_size=1G,hotplugged_size=512M
+```
+
 ## NUMA settings
 
 `NumaConfig` or what is known as `--numa` from the CLI perspective has been

src/main.rs

@@ -109,7 +109,8 @@ fn create_app<'a, 'b>(
                     "Memory parameters \
                      \"size=<guest_memory_size>,mergeable=on|off,shared=on|off,hugepages=on|off,\
                      hotplug_method=acpi|virtio-mem,\
-                     hotplug_size=<hotpluggable_memory_size>\"",
+                     hotplug_size=<hotpluggable_memory_size>,\
+                     hotplugged_size=<hotplugged_memory_size>\"",
                 )
                 .default_value(&default_memory)
                 .group("vm-config"),
@@ -121,7 +122,8 @@ fn create_app<'a, 'b>(
                     "User defined memory zone parameters \
                      \"size=<guest_memory_region_size>,file=<backing_file>,\
                      shared=on|off,hugepages=on|off,host_numa_node=<node_id>,\
-                     id=<zone_identifier>,hotplug_size=<hotpluggable_memory_size>\"",
+                     id=<zone_identifier>,hotplug_size=<hotpluggable_memory_size>,\
+                     hotplugged_size=<hotplugged_memory_size>\"",
                 )
                 .takes_value(true)
                 .min_values(1)
@@ -539,6 +541,7 @@ mod unit_tests {
                     mergeable: false,
                     hotplug_method: HotplugMethod::Acpi,
                     hotplug_size: None,
+                    hotplugged_size: None,
                     shared: false,
                     hugepages: false,
                     balloon: false,

vmm/src/api/openapi/cloud-hypervisor.yaml

@@ -496,6 +496,9 @@ components:
         hotplug_size:
           type: integer
           format: int64
+        hotplugged_size:
+          type: integer
+          format: int64
 
     MemoryConfig:
       required:
@@ -509,6 +512,9 @@ components:
         hotplug_size:
           type: integer
           format: int64
+        hotplugged_size:
+          type: integer
+          format: int64
         mergeable:
           type: boolean
           default: false

vmm/src/config.rs

@@ -381,6 +381,8 @@ pub struct MemoryZoneConfig {
     pub host_numa_node: Option<u32>,
     #[serde(default)]
     pub hotplug_size: Option<u64>,
+    #[serde(default)]
+    pub hotplugged_size: Option<u64>,
 }
 
 #[derive(Clone, Debug, PartialEq, Deserialize, Serialize)]
@@ -393,6 +395,8 @@ pub struct MemoryConfig {
     #[serde(default)]
     pub hotplug_size: Option<u64>,
     #[serde(default)]
+    pub hotplugged_size: Option<u64>,
+    #[serde(default)]
     pub shared: bool,
     #[serde(default)]
     pub hugepages: bool,
@@ -413,6 +417,7 @@ impl MemoryConfig {
             .add("mergeable")
             .add("hotplug_method")
             .add("hotplug_size")
+            .add("hotplugged_size")
             .add("shared")
             .add("hugepages")
             .add("balloon");
@@ -436,6 +441,10 @@ impl MemoryConfig {
             .convert::<ByteSized>("hotplug_size")
             .map_err(Error::ParseMemory)?
             .map(|v| v.0);
+        let hotplugged_size = parser
+            .convert::<ByteSized>("hotplugged_size")
+            .map_err(Error::ParseMemory)?
+            .map(|v| v.0);
         let shared = parser
             .convert::<Toggle>("shared")
             .map_err(Error::ParseMemory)?
@@ -463,7 +472,8 @@ impl MemoryConfig {
                     .add("shared")
                     .add("hugepages")
                     .add("host_numa_node")
-                    .add("hotplug_size");
+                    .add("hotplug_size")
+                    .add("hotplugged_size");
                 parser.parse(memory_zone).map_err(Error::ParseMemoryZone)?;
 
                 let id = parser.get("id").ok_or(Error::ParseMemoryZoneIdMissing)?;
@@ -490,6 +500,10 @@ impl MemoryConfig {
                     .convert::<ByteSized>("hotplug_size")
                     .map_err(Error::ParseMemoryZone)?
                     .map(|v| v.0);
+                let hotplugged_size = parser
+                    .convert::<ByteSized>("hotplugged_size")
+                    .map_err(Error::ParseMemoryZone)?
+                    .map(|v| v.0);
 
                 zones.push(MemoryZoneConfig {
                     id,
@@ -499,6 +513,7 @@ impl MemoryConfig {
                     hugepages,
                     host_numa_node,
                     hotplug_size,
+                    hotplugged_size,
                 });
             }
             Some(zones)
@@ -511,6 +526,7 @@ impl MemoryConfig {
             mergeable,
             hotplug_method,
             hotplug_size,
+            hotplugged_size,
             shared,
             hugepages,
             balloon,
@@ -527,6 +543,7 @@ impl Default for MemoryConfig {
             mergeable: false,
             hotplug_method: HotplugMethod::Acpi,
             hotplug_size: None,
+            hotplugged_size: None,
             shared: false,
             hugepages: false,
             balloon: false,
@@ -2118,6 +2135,7 @@ mod tests {
                 mergeable: false,
                 hotplug_method: HotplugMethod::Acpi,
                 hotplug_size: None,
+                hotplugged_size: None,
                 shared: false,
                 hugepages: false,
                 balloon: false,

vmm/src/memory_manager.rs

@@ -440,6 +440,32 @@ impl MemoryManager {
                 return Err(Error::InvalidMemoryParameters);
             }
 
+            if let Some(hotplugged_size) = config.hotplugged_size {
+                if let Some(hotplug_size) = config.hotplug_size {
+                    if hotplugged_size > hotplug_size {
+                        error!(
+                            "'hotplugged_size' {} can't be bigger than \
+                            'hotplug_size' {}",
+                            hotplugged_size, hotplug_size,
+                        );
+                        return Err(Error::InvalidMemoryParameters);
+                    }
+                } else {
+                    error!(
+                        "Invalid to define 'hotplugged_size' when there is\
+                        no 'hotplug_size'"
+                    );
+                    return Err(Error::InvalidMemoryParameters);
+                }
+                if config.hotplug_method == HotplugMethod::Acpi {
+                    error!(
+                        "Invalid to define 'hotplugged_size' with hotplug \
+                        method 'acpi'"
+                    );
+                    return Err(Error::InvalidMemoryParameters);
+                }
+            }
+
             // Create a single zone from the global memory config. This lets
             // us reuse the codepath for user defined memory zones.
             let zones = vec![MemoryZoneConfig {
@@ -450,6 +476,7 @@ impl MemoryManager {
                 hugepages: config.hugepages,
                 host_numa_node: None,
                 hotplug_size: config.hotplug_size,
+                hotplugged_size: config.hotplugged_size,
             }];
 
             (config.size, zones)
@@ -485,6 +512,32 @@ impl MemoryManager {
                     error!("Invalid to set ACPI hotplug method for memory zones");
                     return Err(Error::InvalidHotplugMethodWithMemoryZones);
                 }
+
+                if let Some(hotplugged_size) = zone.hotplugged_size {
+                    if let Some(hotplug_size) = zone.hotplug_size {
+                        if hotplugged_size > hotplug_size {
+                            error!(
+                                "'hotplugged_size' {} can't be bigger than \
+                                'hotplug_size' {}",
+                                hotplugged_size, hotplug_size,
+                            );
+                            return Err(Error::InvalidMemoryParameters);
+                        }
+                    } else {
+                        error!(
+                            "Invalid to define 'hotplugged_size' when there is\
+                            no 'hotplug_size' for a memory zone"
+                        );
+                        return Err(Error::InvalidMemoryParameters);
+                    }
+                    if config.hotplug_method == HotplugMethod::Acpi {
+                        error!(
+                            "Invalid to define 'hotplugged_size' with hotplug \
+                            method 'acpi'"
+                        );
+                        return Err(Error::InvalidMemoryParameters);
+                    }
+                }
             }
 
             (total_ram_size, zones)