Add support for snapshot memory backend

client/swagger.yaml

@@ -953,6 +953,25 @@ definitions:
         maximum: 32
         description: Number of vCPUs (either 1 or an even number)
 
+  MemoryBackend:
+    type: object
+    required:
+      - backend_type
+      - backend_path
+    properties:
+      backend_type:
+        type: string
+        enum:
+          - File
+          - Uffd
+      backend_path:
+        type: string
+        description: Based on 'backend_type' it is either
+          1) Path to the file that contains the guest memory to be loaded
+          2) Path to the UDS where a process is listening for a UFFD initialization
+          control payload and open file descriptor that it can use to serve this
+          process's guest memory page faults
+
   Metrics:
     type: object
     description:
@@ -1090,8 +1109,10 @@ definitions:
 
   SnapshotLoadParams:
     type: object
+    description:
+      Defines the configuration used for handling snapshot resume. Exactly one of
+      the two `mem_*` fields must be present in the body of the request.
     required:
-      - mem_file_path
       - snapshot_path
     properties:
       enable_diff_snapshots:
@@ -1100,7 +1121,16 @@ definitions:
           Enable support for incremental (diff) snapshots by tracking dirty guest pages.
       mem_file_path:
         type: string
-        description: Path to the file that contains the guest memory to be loaded.
+        description:
+          Path to the file that contains the guest memory to be loaded.
+          This parameter has been deprecated and is only allowed if
+          `mem_backend` is not present.
+      mem_backend:
+        $ref: "#/definitions/MemoryBackend"
+        description:
+          Configuration for the backend that handles memory load. If this field
+          is specified, `mem_file_path` is forbidden. Either `mem_backend` or
+          `mem_file_path` must be present at a time.
       snapshot_path:
         type: string
         description: Path to the file that contains the microVM state to be loaded.

machine.go

@@ -172,7 +172,7 @@ type Config struct {
 }
 
 func (cfg *Config) hasSnapshot() bool {
-	return cfg.Snapshot.MemFilePath != "" || cfg.Snapshot.SnapshotPath != ""
+	return cfg.Snapshot.GetMemFilePath() != "" || cfg.Snapshot.SnapshotPath != ""
 }
 
 // Validate will ensure that the required fields are set and that
@@ -235,7 +235,7 @@ func (cfg *Config) ValidateLoadSnapshot() error {
 		return fmt.Errorf("socket %s already exists", cfg.SocketPath)
 	}
 
-	if _, err := os.Stat(cfg.Snapshot.MemFilePath); err != nil {
+	if _, err := os.Stat(cfg.Snapshot.GetMemFilePath()); err != nil {
 		return err
 	}
 
@@ -649,7 +649,7 @@ func (m *Machine) startVMM(ctx context.Context) error {
 	return nil
 }
 
-//StopVMM stops the current VMM.
+// StopVMM stops the current VMM.
 func (m *Machine) StopVMM() error {
 	return m.stopVMM()
 }
@@ -1171,7 +1171,8 @@ func (m *Machine) CreateSnapshot(ctx context.Context, memFilePath, snapshotPath
 // loadSnapshot loads a snapshot of the VM
 func (m *Machine) loadSnapshot(ctx context.Context, snapshot *SnapshotConfig) error {
 	snapshotParams := &models.SnapshotLoadParams{
-		MemFilePath:         &snapshot.MemFilePath,
+		MemFilePath:         snapshot.MemFilePath,
+		MemBackend:          snapshot.MemBackend,
 		SnapshotPath:        &snapshot.SnapshotPath,
 		EnableDiffSnapshots: snapshot.EnableDiffSnapshots,
 		ResumeVM:            snapshot.ResumeVM,

opts.go

@@ -16,6 +16,7 @@ package firecracker
 import (
 	"os/exec"
 
+	"github.com/firecracker-microvm/firecracker-go-sdk/client/models"
 	"github.com/sirupsen/logrus"
 )
 
@@ -52,7 +53,9 @@ func WithProcessRunner(cmd *exec.Cmd) Opt {
 // to be passed to LoadSnapshot
 type WithSnapshotOpt func(*SnapshotConfig)
 
-// WithSnapshot will allow for the machine to start using a given snapshot.
+// WithSnapshot will allow for the machine to start using a given snapshot. A
+// UFFD socket file path may be used as memFilePath if a MemoryBackendType opt
+// is passed setting the backend type to models.MemoryBackendBackendTypeUffd.
 func WithSnapshot(memFilePath, snapshotPath string, opts ...WithSnapshotOpt) Opt {
 	return func(m *Machine) {
 		m.Cfg.Snapshot.MemFilePath = memFilePath
@@ -66,3 +69,17 @@ func WithSnapshot(memFilePath, snapshotPath string, opts ...WithSnapshotOpt) Opt
 		m.Handlers.FcInit = loadSnapshotHandlerList
 	}
 }
+
+// MemoryBackendType sets the memory backend type to the given value.
+func MemoryBackendType(typ string) WithSnapshotOpt {
+	return func(cfg *SnapshotConfig) {
+		if cfg.MemBackend == nil {
+			cfg.MemBackend = &models.MemoryBackend{
+				BackendPath: String(cfg.MemFilePath),
+			}
+		}
+		cfg.MemBackend.BackendType = String(typ)
+		// Clear MemFilePath since only one of MemFilePath or MemBackend is allowed.
+		cfg.MemFilePath = ""
+	}
+}

snapshot.go

@@ -13,9 +13,19 @@
 
 package firecracker
 
+import "github.com/firecracker-microvm/firecracker-go-sdk/client/models"
+
 type SnapshotConfig struct {
 	MemFilePath         string
+	MemBackend          *models.MemoryBackend
 	SnapshotPath        string
 	EnableDiffSnapshots bool
 	ResumeVM            bool
 }
+
+func (cfg *SnapshotConfig) GetMemFilePath() string {
+	if cfg.MemBackend != nil && cfg.MemBackend.BackendPath != nil {
+		return *cfg.MemBackend.BackendPath
+	}
+	return cfg.MemFilePath
+}