Add documentation to pm.h on how xen uses PM events (freeze, thaw, restore) to implement Guest VM save/checkpoint/restore functionality. Signed-off-by: Shriram Rajagopalan <rshriram@xxxxxxxxx> --- include/linux/pm.h | 19 +++++++++++++++++++ 1 files changed, 19 insertions(+), 0 deletions(-) diff --git a/include/linux/pm.h b/include/linux/pm.h index dd9c7ab..2ddd9d3 100644 --- a/include/linux/pm.h +++ b/include/linux/pm.h @@ -516,6 +516,25 @@ extern void update_pm_runtime_accounting(struct device *dev); * well as during system sleep states like PM_SUSPEND_STANDBY. They may * be able to use wakeup events to exit from runtime low-power states, * or from system low-power states such as standby or suspend-to-RAM. + * + * Xen Guest Kernels use PM_FREEZE, PM_RESTORE and PM_THAW to implement + * VM save/restore/checkpoint functionality. Save and Restore are somewhat + * similar to hibernate functionality. The sequence of events is shown below: + * dpm_suspend_start(PMSG_FREEZE); + * + * dpm_suspend_noirq(PMSG_FREEZE); + * + * sysdev_suspend(PMSG_FREEZE); + * cancelled = suspend_hypercall() + * sysdev_resume(); + * + * dpm_resume_noirq(cancelled ? PMSG_THAW : PMSG_RESTORE); + * + * dpm_resume_end(cancelled ? PMSG_THAW : PMSG_RESTORE); + * + * If the syspend_hypercall returns 1, it means that the VM was merely + * checkpointed (akin to THAW). If it returns 0, it means the system has been + * fully restored from its on-disk snapshot (akin to RESTORE). */ #ifdef CONFIG_PM_SLEEP -- 1.7.0.4 _______________________________________________ linux-pm mailing list linux-pm@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/linux-pm
