VEP 64: Stop vm with pmsuspend to disk

Signed-off-by: Longchuanzheng <[email protected]>

Author: Longchuanzheng

veps/sig-compute/stop-vm-with-pmsuspend-to-disk/pmsuspend_to_disk_flow.png

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+# VEP #NNNN: Your short, descriptive title
+
+## Release Signoff Checklist
+
+Items marked with (R) are required *prior to targeting to a milestone / release*.
+
+- [x] (R) Enhancement issue created, which links to VEP dir in [kubevirt/enhancements] (not the initial VEP PR)
+- [ ] (R) Target version is explicitly mentioned and approved
+- [ ] (R) Graduation criteria filled
+
+## Overview
+
+libvirt have a pmsuspend interface [https://libvirt.org/html/libvirt-libvirt-domain.html#virDomainPMSuspendForDuration], at least for QEMU with flag `target disk` and `duration 0` we can shutdown a domain with  memory to disk. This can release resources. This proposal try to stop vm with `pmsuspend --target disk duration 0`,which can meet specific needs.
+
+## Motivation
+
+Some users wish to shut down running machines to free up resources, but the virtual machine state remains the same when turned on as when turned off.
+
+## Goals
+
+Add a new way to stop vm in kubevirt. which can make virtual machine state remains the same when turned on as when turned off.
+
+## Non Goals
+
+Add pmsuspend to memery to kubevirt（In my opinion, it can implement like pause）
+
+## Definition of Users
+
+<!--
+Who is this feature set intended for
+-->
+
+## User Stories
+
+A user exec `virtctl pmsuspendToDisk vm.name` commend, the vm stopped with memory state saved, exec `virtctl start vm.name` to start the stopped vm.
+
+## Repos
+
+api for stop vm
+
+## Design
+
+# Implementation Phases
+
+### phase1(send request)
+
+1. pmsuspendToDisk is trigger by add status.VirtualMachineStateChangeRequest.PmsuspendToDisk to vm.
+
+```
+StopRequest  StateChangeRequestAction = "PmsuspendToDisk"
+```
+
+2. vm-controller find this status and add `pmsuspendToDisk = true` for vmi.
+
+3. virt-handler send grpc request to virt-launcher and call libvirt interface.
+
+### phase2(return)
+
+According to my experimental results, there are three possible results.1)vm support command with domain shutdown; 2)command return failed; 3) command return successed while domain still running.
+
+1. command successed domain shutdown
+
+   when domain shutdown, vmi failed, vm Runstrategy update to halted.
+
+2. command return failed
+
+   If command failed. virt-handler get err grpc respond and add `domainpmsuspendTodisk` status for vmi. vm cancel request(delete status.VirtualMachineStateChangeRequest.PmsuspendToDisk in vm)
+
+3. command return successed while domain still running
+
+   We need set a timeout duration (maybe in kubevirt cr), If timeout while domain still running. we also add `domainpmsuspendTodisk` status for vmi and cancel request(delete status.VirtualMachineStateChangeRequest.PmsuspendToDisk in vm) in vm. (If domain shutdown after we cancel vm. We do nothing, just let the previous control logic execution, restart if Runstrategy=always)
+
+   ![](pmsuspend_to_disk_flow.png)
+
+## API Examples
+
+Virtctl stop vm.name -n vm.namespace --suspend-to-disk=true
+
+## Alternatives
+
+<!--
+Outline any alternative designs that have been considered)
+-->
+
+## Scalability
+
+<!--
+Overview of how the design scales)
+-->
+
+## Update/Rollback Compatibility
+
+<!--
+Does this impact update compatibility and how?)
+-->
+
+## Functional Testing Approach
+
+<!--
+An overview on the approaches used to functional test this design)
+-->
+
+## Implementation Phases
+
+<!--
+How/if this design will get broken up into multiple phases)
+-->
+
+## Feature lifecycle Phases
+
+<!--
+How and when will the feature progress through the Alpha, Beta and GA lifecycle phases
+
+Refer to https://github.com/kubevirt/community/blob/main/design-proposals/feature-lifecycle.md#releases for more details
+-->
+
+### Alpha
+
+### Beta
+
+### GA