uffd async pf

resources/seccomp/aarch64-unknown-linux-musl.json

@@ -629,6 +629,19 @@
                     }
                 ]
             },
+            {
+                "syscall": "msync",
+                "comment": "Used to sync memory from mmap to disk",
+                "args": [
+                    {
+                        "index": 2,
+                        "type": "dword",
+                        "op": "eq",
+                        "val": 4,
+                        "comment": "MS_SYNC"
+                    }
+                ]
+            },
             {
                 "syscall": "rt_sigaction",
                 "comment": "rt_sigaction is used by libc::abort during a panic to install the default handler for SIGABRT",

resources/seccomp/x86_64-unknown-linux-musl.json

@@ -260,6 +260,31 @@
                     }
                 ]
             },
+            {
+                "syscall": "msync",
+                "comment": "Used to sync memory from mmap to disk",
+                "args": [
+                    {
+                        "index": 2,
+                        "type": "dword",
+                        "op": "eq",
+                        "val": 4,
+                        "comment": "MS_SYNC"
+                    }
+                ]
+            },
+            {
+                "syscall": "memfd_create",
+                "comment": "Used to create a memory backed file descriptor that can be used to save memory to"
+            },
+            {
+                "syscall": "nanosleep",
+                "comment": "Debugging sleep"
+            },
+            {
+                "syscall": "copy_file_range",
+                "comment": "debugging"
+            },
             {
                 "syscall": "rt_sigaction",
                 "comment": "rt_sigaction is used by libc::abort during a panic to install the default handler for SIGABRT",

src/api_server/src/parsed_request.rs

@@ -21,6 +21,7 @@ use crate::request::logger::parse_put_logger;
 use crate::request::machine_configuration::{
     parse_get_machine_config, parse_patch_machine_config, parse_put_machine_config,
 };
+use crate::request::memory_backend::parse_put_memory_backend;
 use crate::request::metrics::parse_put_metrics;
 use crate::request::mmds::{parse_get_mmds, parse_patch_mmds, parse_put_mmds};
 use crate::request::net::{parse_patch_net, parse_put_net};
@@ -91,6 +92,7 @@ impl TryFrom<&Request> for ParsedRequest {
             (Method::Put, "drives", Some(body)) => parse_put_drive(body, path_tokens.next()),
             (Method::Put, "logger", Some(body)) => parse_put_logger(body),
             (Method::Put, "machine-config", Some(body)) => parse_put_machine_config(body),
+            (Method::Put, "memory-backend", Some(body)) => parse_put_memory_backend(body),
             (Method::Put, "metrics", Some(body)) => parse_put_metrics(body),
             (Method::Put, "mmds", Some(body)) => parse_put_mmds(body, path_tokens.next()),
             (Method::Put, "network-interfaces", Some(body)) => {

src/api_server/src/request/memory_backend.rs

@@ -0,0 +1,46 @@
+// Copyright 2018 Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+use super::super::VmmAction;
+use crate::parsed_request::{Error, ParsedRequest};
+use crate::request::Body;
+use vmm::logger::{IncMetric, METRICS};
+use vmm::vmm_config::snapshot::MemBackendConfig;
+
+pub(crate) fn parse_put_memory_backend(body: &Body) -> Result<ParsedRequest, Error> {
+    METRICS.put_api_requests.memory_backend_cfg_count.inc();
+    Ok(ParsedRequest::new_sync(VmmAction::SetMemoryBackend(
+        serde_json::from_slice::<MemBackendConfig>(body.raw()).map_err(|e| {
+            METRICS.put_api_requests.memory_backend_cfg_fails.inc();
+            Error::SerdeJson(e)
+        })?,
+    )))
+}
+
+#[cfg(test)]
+mod tests {
+    use std::path::PathBuf;
+
+    use vmm::vmm_config::snapshot::MemBackendType;
+
+    use super::*;
+
+    #[test]
+    fn test_parse_memory_backing_file() {
+        assert!(parse_put_memory_backend(&Body::new("invalid_payload")).is_err());
+
+        let body = r#"{
+                "backend_type": "File",
+                "backend_path": "./memory.snap"
+              }"#;
+        let same_body = MemBackendConfig {
+            backend_type: MemBackendType::File,
+            backend_path: PathBuf::from("./memory.snap"),
+        };
+        let result = parse_put_memory_backend(&Body::new(body));
+        assert!(result.is_ok());
+        let parsed_req = result.unwrap_or_else(|_e| panic!("Failed test."));
+
+        assert!(parsed_req == ParsedRequest::new_sync(VmmAction::SetMemoryBackend(same_body)));
+    }
+}

src/api_server/src/request/mod.rs

@@ -10,6 +10,7 @@ pub mod entropy;
 pub mod instance_info;
 pub mod logger;
 pub mod machine_configuration;
+pub mod memory_backend;
 pub mod metrics;
 pub mod mmds;
 pub mod net;

src/api_server/swagger/firecracker.yaml

@@ -376,6 +376,29 @@ paths:
           description: Internal server error
           schema:
             $ref: "#/definitions/Error"
+
+  /memory-backend:
+    put:
+      summary: Configures a memory backend to sync the memory changes from during the runtime of the vm
+      operationId: putMemoryBackend
+      parameters:
+        - name: body
+          in: body
+          description: The memory backend to use
+          required: true
+          schema:
+            $ref: "#/definitions/MemoryBackend"
+      responses:
+        204:
+          description: Memory backend configured
+        400:
+          description: Memory backend failed
+          schema:
+            $ref: "#/definitions/Error"
+        default:
+          description: Internal server error.
+          schema:
+            $ref: "#/definitions/Error"
 
   /metrics:
     put:

src/firecracker/Cargo.toml

@@ -28,11 +28,16 @@ vmm = { path = "../vmm" }
 
 [dev-dependencies]
 cargo_toml = "0.16.0"
-regex = { version = "1.9.5", default-features = false, features = ["std", "unicode-perl"] }
+regex = { version = "1.9.5", default-features = false, features = [
+  "std",
+  "unicode-perl",
+] }
 
 # Dev-Dependencies for uffd examples
 serde = { version = "1.0.188", features = ["derive"] }
-userfaultfd = "0.7.0"
+userfaultfd = { git = "https://github.com/codesandbox/userfaultfd-rs.git", rev = "27b2ff3bc71774b79338afca051d49cb07146d90", features = [
+  "linux5_7",
+] }
 
 [build-dependencies]
 bincode = "1.2.1"

src/jailer/src/env.rs

@@ -467,7 +467,7 @@ impl Env {
         //    section), this latter part is not desirable in Firecracker's
         //    threat model. Copying prevents 2 Firecracker processes from
         //    sharing memory.
-        fs::copy(&self.exec_file_path, &self.chroot_dir).map_err(|err| {
+        fs::hard_link(&self.exec_file_path, &self.chroot_dir).map_err(|err| {
             JailerError::Copy(self.exec_file_path.clone(), self.chroot_dir.clone(), err)
         })?;
 

src/snapshot/src/lib.rs

@@ -218,9 +218,10 @@ impl Snapshot {
         object
             .serialize(&mut writer, &self.version_map, self.target_version)
             .map_err(Error::Versionize)?;
-        writer
-            .flush()
-            .map_err(|ref err| Error::Io(err.raw_os_error().unwrap_or(libc::EINVAL)))
+        // writer
+        //     .flush()
+        //     .map_err(|ref err| Error::Io(err.raw_os_error().unwrap_or(libc::EINVAL)))
+        Ok(())
     }
 
     // Returns the current snapshot format version.

src/utils/src/vm_memory.rs

@@ -120,7 +120,7 @@ pub fn create_guest_memory(
     for region in regions {
         let flags = match region.0 {
             None => libc::MAP_NORESERVE | libc::MAP_PRIVATE | libc::MAP_ANONYMOUS,
-            Some(_) => libc::MAP_NORESERVE | libc::MAP_PRIVATE,
+            Some(_) => libc::MAP_NORESERVE | libc::MAP_SHARED,
         };
 
         let mmap_region =

src/vmm/Cargo.toml

@@ -11,7 +11,10 @@ bench = false
 [dependencies]
 aws-lc-rs = "1.0.2"
 bitflags = "2.0.2"
-derive_more = { version = "0.99.17", default-features = false, features = ["from", "display"] }
+derive_more = { version = "0.99.17", default-features = false, features = [
+  "from",
+  "display",
+] }
 event-manager = "0.3.0"
 kvm-bindings = { version = "0.6.0", features = ["fam-wrappers"] }
 kvm-ioctls = "0.15.0"
@@ -24,21 +27,23 @@ serde_json = "1.0.78"
 timerfd = "1.5.0"
 thiserror = "1.0.32"
 displaydoc = "0.2.4"
-userfaultfd = "0.7.0"
+userfaultfd = { git = "https://github.com/codesandbox/userfaultfd-rs.git", rev = "27b2ff3bc71774b79338afca051d49cb07146d90", features = [
+  "linux5_7",
+] }
 versionize = "0.1.10"
 versionize_derive = "0.1.5"
 vm-allocator = "0.1.0"
 vm-fdt = "0.2.0"
 vm-superio = "0.7.0"
 log = { version = "0.4.17", features = ["std", "serde"] }
-aes-gcm =  { version = "0.10.1", default-features = false, features = ["aes"] }
+aes-gcm = { version = "0.10.1", default-features = false, features = ["aes"] }
 base64 = "0.13.0"
 bincode = "1.2.1"
 micro_http = { git = "https://github.com/firecracker-microvm/micro-http" }
 
 net_gen = { path = "../net_gen" }
 seccompiler = { path = "../seccompiler" }
-snapshot = { path = "../snapshot"}
+snapshot = { path = "../snapshot" }
 utils = { path = "../utils" }
 virtio_gen = { path = "../virtio_gen" }