Use kernel paging for Cloud Hypervisor restores

lib/hypervisor/cloudhypervisor/cloudhypervisor.go

@@ -8,6 +8,7 @@ import (
 	"time"
 
 	"github.com/kernel/hypeman/lib/hypervisor"
+	"github.com/kernel/hypeman/lib/logger"
 	"github.com/kernel/hypeman/lib/vmm"
 )
 
@@ -70,6 +71,7 @@ func CapabilitiesForVersion(v vmm.CHVersion) hypervisor.Capabilities {
 	switch v {
 	case vmm.V51_1:
 		caps.SupportsDiskResize = true
+		caps.SupportsConcurrentForkPrepare = true
 	}
 	return caps
 }
@@ -170,6 +172,13 @@ func (c *CloudHypervisor) Snapshot(ctx context.Context, destPath string) error {
 	if resp.StatusCode() != 204 {
 		return fmt.Errorf("snapshot failed with status %d", resp.StatusCode())
 	}
+	optimized, err := prepareSnapshotForKernelPaging(destPath)
+	if err != nil {
+		return fmt.Errorf("prepare kernel-paged snapshot: %w", err)
+	}
+	if optimized {
+		logger.FromContext(ctx).DebugContext(ctx, "prepared Cloud Hypervisor snapshot for kernel paging", "snapshot_dir", destPath)
+	}
 	return nil
 }
 

lib/hypervisor/cloudhypervisor/config.go

@@ -25,6 +25,8 @@ func serialSocketPath(logPath string) string {
 	return filepath.Join(filepath.Dir(filepath.Dir(logPath)), "serial.sock")
 }
 
+const kernelPagingMemoryZoneID = "hypeman-kernel-paging"
+
 // ToVMConfig converts hypervisor.VMConfig to Cloud Hypervisor's vmm.VmConfig.
 func ToVMConfig(cfg hypervisor.VMConfig) vmm.VmConfig {
 	// Payload configuration (kernel + initramfs)
@@ -51,8 +53,21 @@ func ToVMConfig(cfg hypervisor.VMConfig) vmm.VmConfig {
 	}
 
 	// Memory configuration
-	memory := vmm.MemoryConfig{
-		Size: cfg.MemoryBytes,
+	memory := vmm.MemoryConfig{Size: cfg.MemoryBytes}
+	if cfg.MemoryBackingFile != "" {
+		zones := []vmm.MemoryZoneConfig{{
+			Id:        kernelPagingMemoryZoneID,
+			Size:      cfg.MemoryBytes,
+			File:      ptr(cfg.MemoryBackingFile),
+			Shared:    ptr(false),
+			Prefault:  ptr(false),
+			Hugepages: ptr(false),
+		}}
+		memory.Size = 0
+		memory.Shared = ptr(false)
+		memory.Prefault = ptr(false)
+		memory.Hugepages = ptr(false)
+		memory.Zones = &zones
 	}
 	if cfg.HotplugBytes > 0 {
 		memory.HotplugSize = &cfg.HotplugBytes

lib/hypervisor/cloudhypervisor/config_test.go

@@ -8,6 +8,32 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
+func TestToVMConfigFileBackedMemory(t *testing.T) {
+	t.Parallel()
+
+	vmCfg := ToVMConfig(hypervisor.VMConfig{
+		VCPUs:             2,
+		MemoryBytes:       8 * 1024 * 1024 * 1024,
+		MemoryBackingFile: "/var/lib/hypeman/memory.raw",
+	})
+
+	require.NotNil(t, vmCfg.Memory)
+	assert.Zero(t, vmCfg.Memory.Size)
+	require.NotNil(t, vmCfg.Memory.Zones)
+	require.Len(t, *vmCfg.Memory.Zones, 1)
+	zone := (*vmCfg.Memory.Zones)[0]
+	assert.Equal(t, kernelPagingMemoryZoneID, zone.Id)
+	assert.Equal(t, int64(8*1024*1024*1024), zone.Size)
+	require.NotNil(t, zone.File)
+	assert.Equal(t, "/var/lib/hypeman/memory.raw", *zone.File)
+	require.NotNil(t, zone.Shared)
+	assert.False(t, *zone.Shared)
+	require.NotNil(t, zone.Prefault)
+	assert.False(t, *zone.Prefault)
+	require.NotNil(t, zone.Hugepages)
+	assert.False(t, *zone.Hugepages)
+}
+
 func TestToVMConfig_GuestMemoryBalloon(t *testing.T) {
 	cfg := hypervisor.VMConfig{
 		VCPUs:       1,