* [PATCH qemu-server 1/2] fix #5032: qemu: sync guest time on resume and snapshot of saved state
2026-06-12 12:29 [PATCH manager/qemu-server 0/2] fix #5032: sync guest time after restore from saved state Jakob Klocker
@ 2026-06-12 12:29 ` Jakob Klocker
2026-06-12 12:29 ` [PATCH pve-manager 2/2] fix #5032: ui: qemu agent: add set-time-on-resume option Jakob Klocker
1 sibling, 0 replies; 3+ messages in thread
From: Jakob Klocker @ 2026-06-12 12:29 UTC (permalink / raw)
To: pve-devel; +Cc: Jakob Klocker
When a VM is resumed from a saved state (hibernation or snapshot with
RAM), the guest clock may be stale. A time skew can occur when
creating a snapshot of a running VM.
Add a new agent option `set-time-on-resume` to automatically
synchronize the guest time with the host using the QEMU Guest Agent.
Trigger time synchronization:
- after restoring a VM from a saved state or snapshot with RAM
- after taking a snapshot
This ensures consistent guest time after rollback, restore, or
snapshot operations when the guest OS clock does not automatically
correct itself.
Link: https://bugzilla.proxmox.com/show_bug.cgi?id=5032
Signed-off-by: Jakob Klocker <j.klocker@proxmox.com>
---
src/PVE/QemuConfig.pm | 7 ++++++
src/PVE/QemuServer.pm | 10 ++++++++
src/PVE/QemuServer/Agent.pm | 47 +++++++++++++++++++++++++++++++++++++
3 files changed, 64 insertions(+)
diff --git a/src/PVE/QemuConfig.pm b/src/PVE/QemuConfig.pm
index 80a3999e..1950c328 100644
--- a/src/PVE/QemuConfig.pm
+++ b/src/PVE/QemuConfig.pm
@@ -383,6 +383,13 @@ sub __snapshot_create_vol_snapshots_hook {
next;
}
}
+ if ($snap->{vmstate}) {
+ my $conf = $class->load_config($vmid);
+ if (PVE::QemuServer::Agent::should_set_time_on_resume($conf->{agent})) {
+ eval { PVE::QemuServer::Agent::guest_set_time($vmid); 1 }
+ or warn "could not sync guest time after snapshot - $@";
+ }
+ }
}
}
}
diff --git a/src/PVE/QemuServer.pm b/src/PVE/QemuServer.pm
index 239b0cab..99bdd9f5 100644
--- a/src/PVE/QemuServer.pm
+++ b/src/PVE/QemuServer.pm
@@ -5983,6 +5983,16 @@ sub vm_start_nolock {
);
}
+ my $from_saved_state = $resume || ($statefile && !$migratedfrom);
+
+ if (
+ $from_saved_state
+ && PVE::QemuServer::Agent::should_set_time_on_resume($conf->{agent})
+ ) {
+ eval { PVE::QemuServer::Agent::guest_set_time($vmid); 1 }
+ or warn "could not sync guest time after snapshot - $@";
+ }
+
return $res;
}
diff --git a/src/PVE/QemuServer/Agent.pm b/src/PVE/QemuServer/Agent.pm
index be6df443..be8bbae6 100644
--- a/src/PVE/QemuServer/Agent.pm
+++ b/src/PVE/QemuServer/Agent.pm
@@ -4,6 +4,7 @@ use v5.36;
use JSON;
use MIME::Base64 qw(decode_base64 encode_base64);
+use Time::HiRes ();
use PVE::JSONSchema;
@@ -18,6 +19,8 @@ our @EXPORT_OK = qw(
get_qga_key
parse_guest_agent
qga_check_running
+ should_set_time_on_resume
+ guest_set_time
);
our $agent_fmt = {
@@ -52,6 +55,21 @@ our $agent_fmt = {
optional => 1,
default => 1,
},
+ 'set-time-on-resume' => {
+ description => "Update the guest clock through QGA after resuming from"
+ . " hibernation or rolling back to a snapshot with RAM.",
+ verbose_description =>
+ "Whether to issue the guest-set-time QEMU guest agent command after the VM"
+ . " resumes with a restored RAM state, that is, when waking from hibernation"
+ . " or after rolling back to a snapshot that includes RAM. In these cases the"
+ . " guest's clock still reflects the time the state was saved. With this"
+ . " option enabled, the clock is synchronized to the host's current time,"
+ . " provided the QEMU Guest Agent option is enabled in the guest's"
+ . " configuration and the agent is running inside of the guest.",
+ type => 'boolean',
+ optional => 1,
+ default => 1,
+ },
type => {
description => "Select the agent type",
type => 'string',
@@ -332,4 +350,33 @@ sub guest_fs_freeze_applicable($agent_str, $vmid, $logfunc = undef) {
return 1;
}
+=head3 should_set_time_on_resume
+
+Returns whether the guest's clock should be synchronized to the host's via the QEMU Guest Agent
+when the VM is resumed from saved state. Does B<not> check whether the agent is actually running.
+
+=cut
+
+sub should_set_time_on_resume($agent_str) {
+ my $agent = parse_guest_agent($agent_str);
+ return 0 if !$agent->{enabled};
+ return $agent->{'set-time-on-resume'} // 1;
+}
+
+=head3 guest_set_time
+
+Sets the guest's clock via the QEMU Guest Agent's C<guest-set-time> command. If C<$time_ns>
+(nanoseconds since the UNIX epoch, UTC) is not given, the current host time is used. Passing
+an explicit time is required because the agent's argument-less form reads the guest's RTC,
+which may itself be stale after a vmstate snapshot or resume.
+
+=cut
+
+sub guest_set_time($vmid, $time_ns = undef) {
+ $time_ns //= int(Time::HiRes::time() * 1_000_000_000);
+ my $res = PVE::QemuServer::Monitor::mon_cmd($vmid, 'guest-set-time', time => $time_ns);
+ check_agent_error($res, "unable to set guest time");
+ return;
+}
+
1;
--
2.47.3
^ permalink raw reply related [flat|nested] 3+ messages in thread* [PATCH pve-manager 2/2] fix #5032: ui: qemu agent: add set-time-on-resume option
2026-06-12 12:29 [PATCH manager/qemu-server 0/2] fix #5032: sync guest time after restore from saved state Jakob Klocker
2026-06-12 12:29 ` [PATCH qemu-server 1/2] fix #5032: qemu: sync guest time on resume and snapshot of " Jakob Klocker
@ 2026-06-12 12:29 ` Jakob Klocker
1 sibling, 0 replies; 3+ messages in thread
From: Jakob Klocker @ 2026-06-12 12:29 UTC (permalink / raw)
To: pve-devel; +Cc: Jakob Klocker
Expose the new agent configuration option `set-time-on-resume`
in the VM configuration GUI.
This allows enabling/disabling automatic guest clock
synchronization after resume from saved state or snapshot
restore with RAM.
Link: https://bugzilla.proxmox.com/show_bug.cgi?id=5032
Signed-off-by: Jakob Klocker <j.klocker@proxmox.com>
---
www/manager6/Utils.js | 2 ++
www/manager6/form/AgentFeatureSelector.js | 18 ++++++++++++++++++
2 files changed, 20 insertions(+)
diff --git a/www/manager6/Utils.js b/www/manager6/Utils.js
index 2ed4e65d..ee55a6ac 100644
--- a/www/manager6/Utils.js
+++ b/www/manager6/Utils.js
@@ -523,6 +523,8 @@ Ext.define('PVE.Utils', {
continue;
} else if (key === 'freeze-fs' && PVE.Parser.parseBoolean(value)) {
continue;
+ } else if (key === 'set-time-on-resume' && PVE.Parser.parseBoolean(value)) {
+ continue;
} else if (PVE.Parser.parseBoolean(value)) {
displayText = Proxmox.Utils.enabledText;
}
diff --git a/www/manager6/form/AgentFeatureSelector.js b/www/manager6/form/AgentFeatureSelector.js
index 3cae4194..ba21a383 100644
--- a/www/manager6/form/AgentFeatureSelector.js
+++ b/www/manager6/form/AgentFeatureSelector.js
@@ -45,6 +45,18 @@ Ext.define('PVE.form.AgentFeatureSelector', {
hidden: '{freeze_fs.checked}',
},
},
+ {
+ xtype: 'proxmoxcheckbox',
+ boxLabel: gettext('Set guest clock to host after resume from saved state'),
+ name: 'set-time-on-resume',
+ reference: 'set_time_on_resume',
+ bind: {
+ disabled: '{!enabled.checked}',
+ },
+ disabled: true,
+ uncheckedValue: '0',
+ defaultValue: '1',
+ },
{
xtype: 'displayfield',
userCls: 'pmx-hint',
@@ -74,6 +86,9 @@ Ext.define('PVE.form.AgentFeatureSelector', {
if (PVE.Parser.parseBoolean(values['freeze-fs'])) {
delete values['freeze-fs'];
}
+ if (PVE.Parser.parseBoolean(values['set-time-on-resume'])) {
+ delete values['set-time-on-resume'];
+ }
const agentstr = PVE.Parser.printPropertyString(values, 'enabled');
return { agent: agentstr };
@@ -90,6 +105,9 @@ Ext.define('PVE.form.AgentFeatureSelector', {
if (!Ext.isDefined(res['freeze-fs'])) {
res['freeze-fs'] = 1;
}
+ if (!Ext.isDefined(res['set-time-on-resume'])) {
+ res['set-time-on-resume'] = 1;
+ }
this.callParent([res]);
},
--
2.47.3
^ permalink raw reply related [flat|nested] 3+ messages in thread