From 1fc6a13662d36cae8cb212a51e43666216a17e7e Mon Sep 17 00:00:00 2001
From: Shreyansh Sancheti <shsancheti@microsoft.com>
Date: Tue, 21 Jul 2026 14:19:56 +0530
Subject: [PATCH] fix(lcow/v2): report physically backed VM stats

Signed-off-by: Shreyansh Sancheti <shsancheti@microsoft.com>
---
 internal/controller/vm/save_lcow.go    |  4 +-
 internal/controller/vm/vm.go           | 16 ++++----
 internal/controller/vm/vm_lcow.go      | 10 ++++-
 internal/controller/vm/vm_lcow_test.go | 53 ++++++++++++++++++++++++++
 4 files changed, 70 insertions(+), 13 deletions(-)
 create mode 100644 internal/controller/vm/vm_lcow_test.go

diff --git a/internal/controller/vm/save_lcow.go b/internal/controller/vm/save_lcow.go
index 29f330c74a..46243967a8 100644
--- a/internal/controller/vm/save_lcow.go
+++ b/internal/controller/vm/save_lcow.go
@@ -138,9 +138,6 @@ func (c *Controller) Import(ctx context.Context, env *anypb.Any) error {
 	// the controller migrating so only migration APIs are permitted.
 	c.vmID = state.GetVmID()
 	c.sandboxOptions = sandboxOptionsFromProto(state.GetSandboxOptions())
-	if c.sandboxOptions != nil {
-		c.isPhysicallyBacked = c.sandboxOptions.FullyPhysicallyBacked
-	}
 	c.nextGuestPort = state.GetGcsNextPort()
 	c.nextBridgeID = state.GetBridgeNextID()
 	c.compatInfo = state.GetCompatInfo()
@@ -155,6 +152,7 @@ func (c *Controller) Import(ctx context.Context, env *anypb.Any) error {
 		}
 
 		c.hcsDocument = doc
+		c.isPhysicallyBacked = isMemoryPhysicallyBacked(doc)
 	}
 
 	// Import the SCSI sub-controller.
diff --git a/internal/controller/vm/vm.go b/internal/controller/vm/vm.go
index 4dd2cedf85..cd3f921ab4 100644
--- a/internal/controller/vm/vm.go
+++ b/internal/controller/vm/vm.go
@@ -530,15 +530,6 @@ func (c *Controller) Stats(ctx context.Context) (*stats.VirtualMachineStatistics
 		return nil, fmt.Errorf("cannot get stats: VM is in incorrect state %s", c.vmState)
 	}
 
-	// Initialization of vmmemProcess to calculate stats properly for VA-backed UVMs.
-	if c.vmmemProcess == 0 {
-		vmmemHandle, err := vmutils.LookupVMMEM(ctx, c.uvm.RuntimeID(), &iwin.WinAPI{})
-		if err != nil {
-			return nil, fmt.Errorf("cannot get stats: %w", err)
-		}
-		c.vmmemProcess = vmmemHandle
-	}
-
 	s := &stats.VirtualMachineStatistics{}
 	props, err := c.uvm.PropertiesV2(ctx, hcsschema.PTStatistics, hcsschema.PTMemory)
 	if err != nil {
@@ -553,6 +544,13 @@ func (c *Controller) Stats(ctx context.Context) (*stats.VirtualMachineStatistics
 		// working set size for a VA-backed UVM. To work around this, we instead
 		// locate the vmmem process for the VM, and query that process's working set
 		// instead, which will be the working set for the VM.
+		if c.vmmemProcess == 0 {
+			vmmemHandle, err := vmutils.LookupVMMEM(ctx, c.uvm.RuntimeID(), &iwin.WinAPI{})
+			if err != nil {
+				return nil, fmt.Errorf("cannot get stats: %w", err)
+			}
+			c.vmmemProcess = vmmemHandle
+		}
 		memCounters, err := process.GetProcessMemoryInfo(c.vmmemProcess)
 		if err != nil {
 			return nil, err
diff --git a/internal/controller/vm/vm_lcow.go b/internal/controller/vm/vm_lcow.go
index 3c548df04c..720b3c4170 100644
--- a/internal/controller/vm/vm_lcow.go
+++ b/internal/controller/vm/vm_lcow.go
@@ -56,11 +56,19 @@ func (c *Controller) buildHCSConfig(ctx context.Context, opts *CreateOptions) (*
 	}
 
 	c.sandboxOptions = sandboxOptions
-	c.isPhysicallyBacked = sandboxOptions.FullyPhysicallyBacked
+	c.isPhysicallyBacked = isMemoryPhysicallyBacked(hcsDocument)
 
 	return hcsDocument, nil
 }
 
+func isMemoryPhysicallyBacked(doc *hcsschema.ComputeSystem) bool {
+	return doc != nil &&
+		doc.VirtualMachine != nil &&
+		doc.VirtualMachine.ComputeTopology != nil &&
+		doc.VirtualMachine.ComputeTopology.Memory != nil &&
+		!doc.VirtualMachine.ComputeTopology.Memory.AllowOvercommit
+}
+
 // buildConfidentialOptions builds confidential options from the stored sandbox options.
 func (c *Controller) buildConfidentialOptions(ctx context.Context) (*guestresource.ConfidentialOptions, error) {
 	if c.sandboxOptions == nil || c.sandboxOptions.ConfidentialConfig == nil {
diff --git a/internal/controller/vm/vm_lcow_test.go b/internal/controller/vm/vm_lcow_test.go
new file mode 100644
index 0000000000..9c97f63c33
--- /dev/null
+++ b/internal/controller/vm/vm_lcow_test.go
@@ -0,0 +1,53 @@
+//go:build windows && lcow
+
+package vm
+
+import (
+	"testing"
+
+	hcsschema "github.com/Microsoft/hcsshim/internal/hcs/schema2"
+)
+
+func TestIsMemoryPhysicallyBacked(t *testing.T) {
+	tests := []struct {
+		name string
+		doc  *hcsschema.ComputeSystem
+		want bool
+	}{
+		{
+			name: "missing memory topology",
+			doc:  &hcsschema.ComputeSystem{},
+		},
+		{
+			name: "overcommitted memory",
+			doc: computeSystemWithMemory(&hcsschema.VirtualMachineMemory{
+				AllowOvercommit: true,
+			}),
+		},
+		{
+			name: "non-overcommitted memory",
+			doc: computeSystemWithMemory(&hcsschema.VirtualMachineMemory{
+				AllowOvercommit: false,
+			}),
+			want: true,
+		},
+	}
+
+	for _, test := range tests {
+		t.Run(test.name, func(t *testing.T) {
+			if got := isMemoryPhysicallyBacked(test.doc); got != test.want {
+				t.Fatalf("isMemoryPhysicallyBacked() = %t, want %t", got, test.want)
+			}
+		})
+	}
+}
+
+func computeSystemWithMemory(memory *hcsschema.VirtualMachineMemory) *hcsschema.ComputeSystem {
+	return &hcsschema.ComputeSystem{
+		VirtualMachine: &hcsschema.VirtualMachine{
+			ComputeTopology: &hcsschema.Topology{
+				Memory: memory,
+			},
+		},
+	}
+}