vmm: add prefault option in memory and memory-zone

The argument `prefault` is provided in MemoryManager, but it can
only be used by SGX and restore.
With prefault (MAP_POPULATE) been set, subsequent page faults will
decrease during running, although it will make boot slower.

This commit adds `prefault` in MemoryConfig and MemoryZoneConfig.
To resolve conflict between memory and restore, argument
`prefault` has been changed from `bool` to `Option<bool>`, when
its value is None, config from memory will be used, otherwise
argument in Option will be used.

Signed-off-by: Yu Li <liyu.yukiteru@bytedance.com>

src/main.rs

@@ -163,7 +163,8 @@ fn create_app<'a, 'b>(
                      hugepages=on|off,hugepage_size=<hugepage_size>,\
                      hotplug_method=acpi|virtio-mem,\
                      hotplug_size=<hotpluggable_memory_size>,\
-                     hotplugged_size=<hotplugged_memory_size>\"",
+                     hotplugged_size=<hotplugged_memory_size>,\
+                     prefault=on|off\"",
                 )
                 .default_value(default_memory)
                 .group("vm-config"),
@@ -178,7 +179,8 @@ fn create_app<'a, 'b>(
                      hugepages=on|off,hugepage_size=<hugepage_size>,\
                      host_numa_node=<node_id>,\
                      id=<zone_identifier>,hotplug_size=<hotpluggable_memory_size>,\
-                     hotplugged_size=<hotplugged_memory_size>\"",
+                     hotplugged_size=<hotplugged_memory_size>,\
+                     prefault=on|off\"",
                 )
                 .takes_value(true)
                 .min_values(1)
@@ -644,8 +646,9 @@ mod unit_tests {
                     hotplugged_size: None,
                     shared: false,
                     hugepages: false,
-                    zones: None,
                     hugepage_size: None,
+                    prefault: false,
+                    zones: None,
                 },
                 kernel: Some(KernelConfig {
                     path: PathBuf::from("/path/to/kernel"),

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

@@ -546,6 +546,9 @@ components:
         hotplugged_size:
           type: integer
           format: int64
+        prefault:
+          type: boolean
+          default: false
 
     MemoryConfig:
       required:
@@ -577,6 +580,9 @@ components:
         hugepage_size:
           type: integer
           format: int64
+        prefault:
+          type: boolean
+          default: false
         zones:
           type: array
           items:

vmm/src/config.rs

@@ -491,6 +491,8 @@ pub struct MemoryZoneConfig {
     pub hotplug_size: Option<u64>,
     #[serde(default)]
     pub hotplugged_size: Option<u64>,
+    #[serde(default)]
+    pub prefault: bool,
 }
 
 #[derive(Clone, Debug, PartialEq, Deserialize, Serialize)]
@@ -511,6 +513,8 @@ pub struct MemoryConfig {
     #[serde(default)]
     pub hugepage_size: Option<u64>,
     #[serde(default)]
+    pub prefault: bool,
+    #[serde(default)]
     pub zones: Option<Vec<MemoryZoneConfig>>,
 }
 
@@ -526,7 +530,8 @@ impl MemoryConfig {
             .add("hotplugged_size")
             .add("shared")
             .add("hugepages")
-            .add("hugepage_size");
+            .add("hugepage_size")
+            .add("prefault");
         parser.parse(memory).map_err(Error::ParseMemory)?;
 
         let size = parser
@@ -565,6 +570,11 @@ impl MemoryConfig {
             .convert::<ByteSized>("hugepage_size")
             .map_err(Error::ParseMemory)?
             .map(|v| v.0);
+        let prefault = parser
+            .convert::<Toggle>("prefault")
+            .map_err(Error::ParseMemory)?
+            .unwrap_or(Toggle(false))
+            .0;
 
         let zones: Option<Vec<MemoryZoneConfig>> = if let Some(memory_zones) = &memory_zones {
             let mut zones = Vec::new();
@@ -579,7 +589,8 @@ impl MemoryConfig {
                     .add("hugepage_size")
                     .add("host_numa_node")
                     .add("hotplug_size")
-                    .add("hotplugged_size");
+                    .add("hotplugged_size")
+                    .add("prefault");
                 parser.parse(memory_zone).map_err(Error::ParseMemoryZone)?;
 
                 let id = parser.get("id").ok_or(Error::ParseMemoryZoneIdMissing)?;
@@ -615,6 +626,11 @@ impl MemoryConfig {
                     .convert::<ByteSized>("hotplugged_size")
                     .map_err(Error::ParseMemoryZone)?
                     .map(|v| v.0);
+                let prefault = parser
+                    .convert::<Toggle>("prefault")
+                    .map_err(Error::ParseMemoryZone)?
+                    .unwrap_or(Toggle(false))
+                    .0;
 
                 zones.push(MemoryZoneConfig {
                     id,
@@ -626,6 +642,7 @@ impl MemoryConfig {
                     host_numa_node,
                     hotplug_size,
                     hotplugged_size,
+                    prefault,
                 });
             }
             Some(zones)
@@ -642,6 +659,7 @@ impl MemoryConfig {
             shared,
             hugepages,
             hugepage_size,
+            prefault,
             zones,
         })
     }
@@ -676,6 +694,7 @@ impl Default for MemoryConfig {
             shared: false,
             hugepages: false,
             hugepage_size: None,
+            prefault: false,
             zones: None,
         }
     }
@@ -2678,6 +2697,7 @@ mod tests {
                 shared: false,
                 hugepages: false,
                 hugepage_size: None,
+                prefault: false,
                 zones: None,
             },
             kernel: Some(KernelConfig {

vmm/src/memory_manager.rs

@@ -144,6 +144,7 @@ pub struct MemoryManager {
     shared: bool,
     hugepages: bool,
     hugepage_size: Option<u64>,
+    prefault: bool,
     #[cfg(target_arch = "x86_64")]
     sgx_epc_region: Option<SgxEpcRegion>,
     user_provided_zones: bool,
@@ -399,7 +400,7 @@ impl MemoryManager {
     fn create_memory_regions_from_zones(
         ram_regions: &[(GuestAddress, usize)],
         zones: &[MemoryZoneConfig],
-        prefault: bool,
+        prefault: Option<bool>,
     ) -> Result<(Vec<Arc<GuestRegionMmap>>, MemoryZones), Error> {
         let mut zones = zones.to_owned();
         let mut mem_regions = Vec::new();
@@ -447,7 +448,10 @@ impl MemoryManager {
                     file_offset,
                     region_start,
                     region_size,
-                    prefault,
+                    match prefault {
+                        Some(pf) => pf,
+                        None => zone.prefault,
+                    },
                     zone.shared,
                     zone.hugepages,
                     zone.hugepage_size,
@@ -543,7 +547,7 @@ impl MemoryManager {
     pub fn new(
         vm: Arc<dyn hypervisor::Vm>,
         config: &MemoryConfig,
-        prefault: bool,
+        prefault: Option<bool>,
         phys_bits: u8,
         #[cfg(feature = "tdx")] tdx_enabled: bool,
     ) -> Result<Arc<Mutex<MemoryManager>>, Error> {
@@ -601,6 +605,7 @@ impl MemoryManager {
                 host_numa_node: None,
                 hotplug_size: config.hotplug_size,
                 hotplugged_size: config.hotplugged_size,
+                prefault: config.prefault,
             }];
 
             (config.size, zones)
@@ -716,12 +721,18 @@ impl MemoryManager {
                                 * virtio_devices::VIRTIO_MEM_ALIGN_SIZE,
                         );
 
+                        // When `prefault` is set by vm_restore, memory manager
+                        // will create ram region with `prefault` option in
+                        // restore config rather than same option in zone
                         let region = MemoryManager::create_ram_region(
                             &None,
                             0,
                             start_addr,
                             hotplug_size as usize,
-                            false,
+                            match prefault {
+                                Some(pf) => pf,
+                                None => zone.prefault,
+                            },
                             zone.shared,
                             zone.hugepages,
                             zone.hugepage_size,
@@ -810,6 +821,7 @@ impl MemoryManager {
             shared: config.shared,
             hugepages: config.hugepages,
             hugepage_size: config.hugepage_size,
+            prefault: config.prefault,
             #[cfg(target_arch = "x86_64")]
             sgx_epc_region: None,
             user_provided_zones,
@@ -883,7 +895,7 @@ impl MemoryManager {
         let mm = MemoryManager::new(
             vm,
             config,
-            prefault,
+            Some(prefault),
             phys_bits,
             #[cfg(feature = "tdx")]
             false,
@@ -1123,7 +1135,7 @@ impl MemoryManager {
             0,
             start_addr,
             size,
-            false,
+            self.prefault,
             self.shared,
             self.hugepages,
             self.hugepage_size,

vmm/src/vm.rs

@@ -762,7 +762,7 @@ impl Vm {
         let memory_manager = MemoryManager::new(
             vm.clone(),
             &config.lock().unwrap().memory.clone(),
-            false,
+            None,
             phys_bits,
             #[cfg(feature = "tdx")]
             tdx_enabled,
@@ -886,7 +886,7 @@ impl Vm {
         let memory_manager = MemoryManager::new(
             vm.clone(),
             &config.lock().unwrap().memory.clone(),
-            false,
+            None,
             phys_bits,
             #[cfg(feature = "tdx")]
             false,