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+# Smart Switch Reboot High Level Design
+
+## Table of Contents ##
+
+- [Smart Switch Reboot Design](#smart-switch-reboot-design)
+ - [Table of Contents](#table-of-contents)
+ - [Revision](#revision)
+ - [Glossary](#glossary)
+ - [Overview](#overview)
+ - [Assumptions](#assumptions)
+ - [Requirements](#requirements)
+ - [Methods of Switch and DPU Reboot](#methods-of-switch-and-dpu-reboot)
+ - [DPU reboot sequence](#dpu-reboot-sequence)
+ - [Switch reboot sequence](#switch-reboot-sequence)
+ - [High Level Design](#high-level-design)
+ - [ModuleBase Class API](#modulebase-class-api)
+ - [ModuleBase Class new APIs](#modulebase-class-new-apis)
+ - [NPU platform.json](#npu-platformjson)
+ - [GNOI API implementation](#gnoi-api-implementation)
+ - [reboot CLI modifications](#reboot-cli-modifications)
+ - [reboot script modifications](#reboot-script-modifications)
+ - [PCIe daemon modifications](#pcie-daemon-modifications)
+ - [Error handling and exception scenarios](#error-handling-and-exception-scenarios)
+ - [Test plan](#test-plan)
+ - [References](#references)
+
+## Revision ##
+
+| Rev | Date | Author | Change Description |
+| --- | ---------- | ---------------- | ------------------ |
+| 0.1 | 05/16/2024 | Vasundhara Volam | Initial version |
+| 0.2 | 05/29/2024 | Vasundhara Volam | Update images and APIs |
+| 0.3 | 06/10/2024 | Vasundhara Volam | Minor changes based on discussion with the community |
+| 0.4 | 07/29/2024 | Vasundhara Volam | Add PCIe daemon changes |
+
+## Glossory ##
+
+| Term | Meaning |
+| ----- | ----------------------------------------- |
+| ASIC | Application-Specific Integrated Circuit |
+| DPU | Data Processing Unit |
+| gNMI | gRPC Network Management Interface |
+| gNOI | gRPC Network Operations Interface |
+| NPU | Network Processing Unit |
+| PCI-E | Peripheral Component Interconnect Express |
+
+## Overview ##
+
+Smart Switch aims to provide a full suite of network functionality, like traditional network devices, but with the flexibility
+and scalability of cloud-based services. It consists of one switch ASIC (NPU) and multiple DPUs. The DPU ASICs are only
+connected to the NPU, and all front panel ports are connected to the NPU. The DPU also connects to the SmartSwitch CPU via PCI-E
+interfaces, allowing the Switch CPU to control DPUs through these interfaces.
+
+Each DPU will have one internal management IP which is used for internal communications, such as Redis database and zmq. This
+internal communication is also used between NPU and DPU, and between DPUs.
+
+This document provides high level design of reboot sequence of a SmartSwitch with multiple DPUs and single DPU reboot sequence
+through GNOI API.
+
+## Assumptions ##
+
+Smart Switch supports only cold-reboot and does not support warm-reboot as of today.
+
+## Requirements ##
+
+1. NPU host is running gNOI client to communicate with DPU.
+2. DPU host is running gNOI server to listen to gNOI client requests.
+3. Each DPU is assigned an IP address to communicate from NPU.
+4. SONiC host services on both the NPU and DPU should undergo a graceful shutdown during reboot.
+
+## Methods of Switch and DPU Reboot ##
+
+The switch or DPU can be rebooted using either the CLI or during an image upgrade. The reboot can be initiated in two ways.
+
+1. Performing a complete SmartSwitch reboot, which restarts the NPU and all DPUs.
+2. Rebooting a specific DPU by specifying its ID.
+
+In addition to the previously mentioned causes of graceful reboots, a switch or DPU may also reboot due to events such as power failures during DPU power-up, kernel panics, and other similar incidents.
+
+## DPU reboot sequence ##
+
+
+
+DPUs are internally connected to the NPU via PCI-E bridge. Below is the reboot sequence for rebooting a specific DPU:
+
+* Upon receiving a [reboot](https://github.com/sonic-net/sonic-utilities/blob/master/scripts/reboot) CLI command to restart a particular DPU, the NPU transmits a gNOI Reboot RPC signal with RebootMethod set to ‘HALT’, instructing the DPU to terminate all services.
+
+* Upon dispatching the gNOI Reboot RPC, the NPU issues the gNOI RebootStatus RPC to monitor whether the DPU has terminated all services except gNOI and database
+service, continuing until the timeout is reached. Once the DPU successfully terminates all services, it responds to the gNOI RebootStatus RPC with STATUS_SUCCESS and 'active'
+will be set to false in the RebootStatusResponse. Until the services are terminated gracefully, 'active' will be '1' in the RebootStatusResponse.
+
+* Subsequently, the NPU detaches the DPU PCI device using the sysfs interface by executing `echo 1 > /sys/bus/pci/devices/XXXX:XX:XX.X/remove`. This detachment is currently performed via sysfs, with future plans to implement a vendor-specific API when the DPU bus information cannot have a fixed value.
+
+* Next, the NPU triggers a platform vendor reboot API to initiate the reboot process for the DPU. If the DPU is stuck or unresponsive, the DPU reboot platform API should
+attempt a cold boot or power cycle to recover it.
+
+* The NPU either immediately rescans the PCI bus upon return or after a specified timeout period. This rescan is performed via the sysfs interface by echoing '1' to /sys/bus/pci/rescan.
+
+## Switch reboot sequence ##
+
+
+
+The following outlines the reboot procedure for the entire Smart Switch:
+
+* When the NPU receives a [reboot](https://github.com/sonic-net/sonic-utilities/blob/master/scripts/reboot) command via the CLI to restart the SmartSwitch, it initiates the reboot sequence.
+
+* The NPU sends a gNOI Reboot RPC signal to all connected DPUs in parallel using multiple threads. This signal instructs the DPUs to gracefully terminate all
+services, excluding the gNOI server and also database, in preparation for the reboot.
+
+* Upon dispatching the gNOI Reboot RPC, the NPU issues the gNOI RebootStatus RPC to monitor whether the DPU has terminated all services except GNMI and database
+service, continuing until the timeout is reached. Once the DPU successfully terminates all services, it responds to the gNOI RebootStatus RPC with STATUS_SUCCESS and 'active'
+will be set to false in the RebootStatusResponse. Until the services are terminated gracefully, 'active' will be '1' in the RebootStatusResponse.
+
+* Following the confirmation from the DPUs, the NPU proceeds to detach the PCI devices associated with the DPUs. This detachment is achieved through the sysfs interface by echoing '1' to the /sys/bus/pci/devices/XXXX:XX:XX.X/remove file for each DPU. While this detachment is currently performed via sysfs, there are plans to implement a vendor-specific API for cases where the DPU bus information cannot have a fixed value.
+
+* With the DPUs prepared for reboot, the NPU triggers a platform vendor API to initiate the reboot process for the DPUs. Vendor API reboots a single DPU, but the NPU spawns multiple threads to reboot DPUs in parallel. If any of the the DPU is stuck or unresponsive, the DPU reboot platform API should attempt a cold boot or power cycle to recover it.
+
+* After all the DPUs have rebooted and responded to the platform's reboot vendor API, the NPU will proceed with its own reboot to complete the overall reboot process. The vendor-specific reboot API should include an error handling mechanism to manage DPU reboot failures. Additionally log all the failures. DPUs will be in DPU_READY state, if the reboot happened successfully.
+
+* After a successful reboot, the NPU resumes its operations, and PCI enumeration occurs as part of the reboot process.
+
+## High-Level Design ##
+
+### ModuleBase Class API ###
+
+reboot(self, reboot_type):
+```
+Define new reboot_type as MODULE_REBOOT_DPU for DPU only reboot and MODULE_REBOOT_SMARTSWITCH for entire switch reboot.
+```
+
+This API is defined in [smartswitch-pmon.md](https://github.com/sonic-net/SONiC/blob/master/doc/smart-switch/pmon/smartswitch-pmon.md#:~:text=reboot(self%2C%20reboot_type)%3A)
+
+### ModuleBase Class new APIs ###
+
+pci_detach(self. module_name):
+```
+Detaches the DPU PCI device from the NPU. In the case of non-smart-switch chassis, no action is taken.
+
+Returns:
+ True
+```
+
+pci_reattach(self, module_name):
+```
+Rescans the PCI bus and attach the DPU back to NPU. In the case of non-smart-switch chassis, no action is taken.
+
+Returns:
+ True
+```
+
+get_bus_info(self, module_name):
+```
+For a given DPU module name, retrieve the PCI bus information. In the case of non-smart-switch chassis, no action is taken.
+
+Returns:
+ Returns the PCI bus information in BDF format like "[DDDD:]:BB:SS.F"
+```
+
+### NPU platform.json ###
+
+Introduce a new parameter, 'dpu_halt_services_timeout', to specify the duration(in secs) for waiting for the DPU to terminate all services,
+as defined by the platform vendor. If the DPU fails to respond within this timeout, the NPU will proceed with the reboot sequence. If no timeout is explicitly defined,
+a default timeout will be used.
+
+```json
+{
+ .
+ .
+ "dpu_halt_services_timeout" : "300"
+
+ "DPUS" : [
+ {
+ "dpu0": {
+ "bus_info" : "[DDDD:]BB:SS.F"
+ }
+ },
+ {
+ "dpu1": {
+ "bus_info" : "[DDDD:]BB:SS.F"
+ }
+ },
+ .
+ .
+ {
+ "dpuX": {
+ "bus_info" : "[DDDD:]BB:SS.F"
+ }
+ }
+ ]
+ .
+ .
+}
+```
+
+### GNOI API implementation ###
+
+According to the RebootRequest protocol outlined below, we will utilize the 'HALT' in the RebootMethod to terminate services on the DPU. When the NPU sends the RebootRequest
+with the HALT RebootMethod to the DPU, it will invoke the /usr/local/bin/reboot script to stop all the services except GNMI server and database services. Refer to the
+[gNOI reboot HLD](#https://github.com/sonic-net/SONiC/blob/master/doc/warm-reboot/Warmboot_Manager_HLD.md) for design information of gNOI reboot flow to invoke the
+reboot script in SONiC host services.
+
+```
+*Arguments*: type of reboot (cold, warm, etc.), delay before issuing reboot, string describing reason for reboot, option to force reboot if sanity checks fail.
+
+rpc Reboot(RebootRequest) returns (RebootResponse) {}
+
+message RebootRequest {
+ RebootMethod method = 1;
+ // Delay in nanoseconds before issuing reboot.
+ uint64 delay = 2;
+ // Informational reason for the reboot.
+ string message = 3;
+ // Optional sub-components to reboot.
+ repeated types.Path subcomponents = 4;
+ // Force reboot if sanity checks fail. (ex. uncommited configuration)
+ bool force = 5;
+}
+
+message RebootResponse {
+}
+
+enum RebootMethod {
+ UNKNOWN = 0; // Invalid default method.
+ COLD = 1; // Shutdown and restart OS and all hardware.
+ POWERDOWN = 2; // Halt and power down, if possible.
+ *HALT = 3;* // Halt, if possible.
+ WARM = 4; // Reload configuration but not underlying hardware.
+ NSF = 5; // Non-stop-forwarding reboot, if possible.
+ // RESET method is deprecated in favor of the gNOI FactoryReset.Start().
+ reserved 6;
+ POWERUP = 7; // Apply power, no-op if power is already on.
+}
+```
+
+After receiving the acknowledgement for RebootRequest RPC from the DPU, the NPU starts polling with RebootStatusRequest. If the DPU has effectively terminated
+the services, it responds with STATUS_SUCCESS and 'active' will be set to false in the RebootStatusResponse. Until the services are terminated gracefully,
+'active' will be '1' in the RebootStatusResponse.
+
+```
+rpc RebootStatus(RebootStatusRequest) returns (RebootStatusResponse) {}
+
+message RebootStatusRequest {
+ repeated types.Path subcomponents = 1; // optional sub-component.
+}
+
+message RebootStatusResponse {
+ bool active = 1; // If reboot is active.
+ uint64 wait = 2; // Time left until reboot.
+ uint64 when = 3; // Time to reboot in nanoseconds since the epoch.
+ string reason = 4; // Reason for reboot.
+ uint32 count = 5; // Number of reboots since active.
+ RebootMethod method = 6; // Type of reboot.
+ RebootStatus status = 7; // Applicable only when active = false.
+}
+
+message RebootStatus {
+ enum Status {
+ STATUS_UNKNOWN = 0;
+ STATUS_SUCCESS = 1;
+ STATUS_RETRIABLE_FAILURE = 2;
+ STATUS_FAILURE = 3;
+ }
+ Status status = 1;
+ string message = 2;
+}
+```
+### reboot CLI modifications ###
+
+Introduce a new parameter '-d' to the reboot command for specifying the DPU module name requiring a reboot. If the chassis is
+not a smart switch, this action will have no effect. If the reboot command is executed without specifying any '-d' option, the entire switch will
+be rebooted.
+
+```
+Usage /usr/local/bin/reboot [options]
+ Request rebooting the device. Invoke platform-specific tool when available.
+ This script will shutdown syncd before rebooting.
+
+ Available options:
+ -h, -? : getting this help
+ -f : execute reboot force
+ -d : DPU module name
+ -p : pre-shutdown
+```
+
+### reboot script modifications ###
+
+* Within the reboot() function, incorporate a verification step to invoke is_smartswitch(). Should is_smartswitch() yield false, proceed with the current
+implementation. However, if is_smartswitch() returns true, invoke the new reboot_smartswitch() function, passing a parameter to specify whether it's
+a complete switch reboot or targeting a specific DPU.
+
+* If the reboot_type is ‘REBOOT_TYPE_WARM’ and is_smartswitch is true, return a warning that this type of reboot is not supported.
+
+* Add a new reboot_smartswitch() function to reboot either the entire switch or a particular DPU, which takes DPU ID as an argument that
+needs a reboot.
+
+```
+def reboot_smartswitch(duthost, localhost, reboot_type='cold', reboot_dpu='false', dpu_id='0')
+ """
+ reboots SmartSwitch or a DPU
+ :param duthost: DUT host object
+ :param localhost: local host object
+ :param reboot_type: reboot type (cold)
+ :param reboot_dpu: reboot dpu or switch (true, false)
+ :param dpu_id: reboot the dpu with id, valid only if reboot_dpu is true.
+```
+
+* NPU invokes the reboot script with "-p" option on the DPU via GNOI API to reboot the DPU. When reboot script is invoked with "-p" option,
+execute all the steps except the actual reboot at the end of the script.
+
+* When a DPU module is requested for a reboot, the reboot script will update StateDB with the reboot information according to the schema defined
+below. Define a new function named update_dpu_pcie_info() for this purpose. Additionally, if the entire smart switch is undergoing a reboot,
+update the same information for all the DPUs. Once the DPU is rebooted and the PCIe device is reattached, the StateDB entry will be updated accordingly.
+
+#### PCIE_DETACH_INFO schema in StateDB
+
+```
+"PCIE_DETACH_INFO|DPU_0": {
+ "value": {
+ "dpu_id": "0",
+ "dpu_state": "detaching",
+ "bus_info" : "[DDDD:]BB:SS.F"
+ }
+}
+```
+
+### PCIe daemon modifications ###
+The PCIe daemon will be updated to avoid logging "PCIe Device: Not Found" messages when DPUs are undergoing a reboot, as this is a
+user-initiated action.
+
+In the [check_pci_devices()](#https://github.com/sonic-net/sonic-platform-daemons/blob/bf865c6b711833347d3c57e9d84cd366bcd1b776/sonic-pcied/scripts/pcied#L155) function,
+read the State DB for the PCIE_DETACH_INFO and suppress the "device not found" warning logs during a DPU reboot when the device is intentionally detached.
+
+### Error handling and exception scenarios ###
+
+The following are specific error scenarios where the DPU state will not be DPU_READY.
+
+* If the gNOI service is not operational on the DPU or DPU is unreachable for any reason, detach the PCI, and proceed with the reboot after a timeout
+upon receiving an acknowledgment.
+
+* After the DPU reboots, if the DPU PCI fails to reconnect for any reason, an error-handling mechanism should be in place to restore the DPU.
+
+* If a DPU fails to reboot during a switch reboot, the NPU should attempt to recover the DPU and log any errors that occur.
+
+* In the event of power failure, a power-cycle due to a kernel panic, or any other unknown reason, both the DPU and NPU will undergo an ungraceful reboot.
+
+* In the event of a DPU reboot failure, a hardware watchdog is needed to monitor and reset the DPU. This implementation is vendor-specific.
+
+## Test plan ##
+
+Presented below is the test plan within the ```sonic-mgmt``` framework for the smart switch reboot.
+
+###Graceful boot/reboot###
+
+A graceful boot refers to a controlled and orderly startup process where the system (whether it is a device, DPU, NPU, or the entire system) powers on or reboots without any unexpected interruptions or failures. During a graceful boot, all components follow a well-defined sequence to ensure system stability and functionality.
+
+###Ungraceful boot/reboot###
+
+An ungraceful boot occurs when the boot process is interrupted, incomplete, or initiated in a hasty or unexpected manner, leading to potential system errors or data corruption. This may result from power loss, forced shutdowns, or reboot failures.
+
+
+| Event | NPU reboot sequence | DPU reboot sequence |
+| ----------------------------------------- | ------------------- | ------------------- |
+| Power-On | Graceful boot | Graceful boot |
+| Planned cold reboot of Smart Switch | Graceful reboot | Graceful reboot |
+| Planned cold reboot of DPU | - | Graceful reboot |
+| Planned power-cycle of Smart Switch | Graceful reboot | Graceful reboot |
+| Planned power-cycle of DPU | - | Graceful reboot |
+| Unplanned DPU power failure | - | Ungraceful reboot |
+| Unplanned Smart Switch power failure | Ungraceful reboot | Ungraceful reboot |
+| Unplanned Smart Switch System Crash | Ungraceful reboot | Ungraceful reboot |
+| Unplanned DPU System Crash | - | Ungraceful reboot |
+
+The test scenarios described above ensure that both the NPU and all DPUs are fully operational after any type of reboot. Additionally, the tests verify the following post-reboot conditions:
+
+1. DPUs that were UP before the reboot have successfully come back online.
+2. DPUs that were administratively down remain in the down state after the reboot.
+3. PCI communication between the NPU and any DPUs that are online is functioning correctly.
+4. The cause of the reboot is accurately recorded and updated.
+
+## References
+
+- [PMON HLD](https://github.com/sonic-net/SONiC/blob/master/doc/smart-switch/pmon/smartswitch-pmon.md)
+- [Openconfig system.proto](#https://github.com/openconfig/gnoi/blob/main/system/system.proto)
+- [Warmboot Manager HLD](#https://github.com/sonic-net/SONiC/blob/master/doc/warm-reboot/Warmboot_Manager_HLD.md)
+- [gNOI reboot HLD](#https://github.com/sonic-net/SONiC/blob/master/doc/warm-reboot/Warmboot_Manager_HLD.md)
+- [PCIe daemon](#https://github.com/sonic-net/sonic-platform-daemons/blob/master/sonic-pcied/scripts/pcied)
