From ad909a3d71c6f7db0bd664b3808477a618d331c2 Mon Sep 17 00:00:00 2001
From: Atish Patra <atishp@meta.com>
Date: Thu, 11 Jun 2026 15:03:46 -0700
Subject: [PATCH] vmm: drive guest clock save/restore through the vm
 abstraction

Currently, VM pause/resume/snapshot paths invoke architecture specific
bits for guest clock udpates which ideally belongs to hypervisor layer.

Route it through the snapshot_clock()/restore_clock() pair added in the
previous commit instead, so the VMM no longer depends on an architecture
specific clock API and the upcoming aarch64 backend can hook the same
path without a parallel branch in vm.rs.

Signed-off-by: Atish Patra <atishp@meta.com>
---
 vmm/src/vm.rs | 26 +++++++++++---------------
 1 file changed, 11 insertions(+), 15 deletions(-)

diff --git a/vmm/src/vm.rs b/vmm/src/vm.rs
index d17b92b71..fc2468d58 100644
--- a/vmm/src/vm.rs
+++ b/vmm/src/vm.rs
@@ -529,7 +529,7 @@ pub struct Vm {
     // The hypervisor abstracted virtual machine.
     vm: Arc<dyn hypervisor::Vm>,
     #[cfg(target_arch = "x86_64")]
-    saved_clock: Option<hypervisor::ClockData>,
+    saved_clock: Option<hypervisor::ClockState>,
     #[cfg(not(target_arch = "riscv64"))]
     numa_nodes: NumaNodes,
     #[cfg_attr(any(not(feature = "kvm"), target_arch = "aarch64"), allow(dead_code))]
@@ -3216,14 +3216,10 @@ impl Pausable for Vm {
 
         #[cfg(target_arch = "x86_64")]
         {
-            let mut clock = self
+            self.saved_clock = self
                 .vm
-                .get_clock()
-                .map_err(|e| MigratableError::Pause(anyhow!("Could not get VM clock: {e}")))?;
-            if !clock.has_realtime() {
-                clock.set_realtime(std::time::SystemTime::now());
-            }
-            self.saved_clock = Some(clock);
+                .snapshot_clock()
+                .map_err(|e| MigratableError::Pause(anyhow!("Could not capture guest clock: {e}")))?;
         }
 
         // Before pausing the vCPUs activate any pending virtio devices that might
@@ -3254,14 +3250,14 @@ impl Pausable for Vm {
             .valid_transition(new_state)
             .map_err(|e| MigratableError::Resume(anyhow!("Invalid transition: {e:?}")))?;
 
-        // Restore KVM clock BEFORE vCPUs start running, so they see correct
-        // TSC/kvmclock from the first instruction after resume.
+        // Restore the guest clock BEFORE the vCPUs start running, so they see the
+        // corrected time from the first instruction after resume.
         #[cfg(target_arch = "x86_64")]
         {
-            if let Some(clock) = &self.saved_clock {
-                self.vm
-                    .set_clock(clock)
-                    .map_err(|e| MigratableError::Resume(anyhow!("Could not set VM clock: {e}")))?;
+            if let Some(state) = &self.saved_clock {
+                self.vm.restore_clock(state).map_err(|e| {
+                    MigratableError::Resume(anyhow!("Could not restore guest clock: {e}"))
+                })?;
             }
         }
 
@@ -3284,7 +3280,7 @@ impl Pausable for Vm {
 #[derive(Serialize, Deserialize)]
 pub struct VmSnapshot {
     #[cfg(target_arch = "x86_64")]
-    pub clock: Option<hypervisor::ClockData>,
+    pub clock: Option<hypervisor::ClockState>,
     #[cfg(all(feature = "kvm", target_arch = "x86_64"))]
     pub common_cpuid: Vec<hypervisor::arch::x86::CpuIdEntry>,
 }