From: Jakub Kicinski Date: Tue, 3 Feb 2026 02:06:02 +0000 (-0800) Subject: Merge branch 'ptp-vmclock-add-vm-generation-counter-and-acpi-notification' X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=74ad1dfe2335df7c1fd36139261c2fba6bcaea40;p=thirdparty%2Fkernel%2Flinux.git Merge branch 'ptp-vmclock-add-vm-generation-counter-and-acpi-notification' Takahiro Itazuri says: ==================== ptp: vmclock: Add VM generation counter and ACPI notification Similarly to live migration, starting a VM from some serialized state (aka snapshot) is an event which calls for adjusting guest clocks, hence a hypervisor should increase the disruption_marker before resuming the VM vCPUs, letting the guest know. However, loading a snapshot, is slightly different than live migration, especially since we can start multiple VMs from the same serialized state. Apart from adjusting clocks, the guest needs to take additional action during such events, e.g. recreate UUIDs, reset network adapters/connections, reseed entropy pools, etc. These actions are not necessary during live migration. This calls for a differentiation between the two triggering events. We differentiate between the two events via an extra field in the vmclock_abi, called vm_generation_counter. Whereas hypervisors should increase the disruption marker in both cases, they should only increase vm_generation_counter when a snapshot is loaded in a VM (not during live migration). Additionally, we attach an ACPI notification to VMClock. Implementing the notification is optional for the device. VMClock device will declare that it implements the notification by setting VMCLOCK_FLAG_NOTIFICATION_PRESENT bit in vmclock_abi flags. Hypervisors that implement the notification must send an ACPI notification every time seq_count changes to an even number. The driver will propagate these notifications to userspace via the poll() interface. ==================== Link: https://patch.msgid.link/20260130173704.12575-1-itazur@amazon.com Signed-off-by: Jakub Kicinski --- 74ad1dfe2335df7c1fd36139261c2fba6bcaea40