Intel® Arria® 10 Hard Processor System Technical Reference Manual

ID 683711
Date 8/28/2023
Public
Document Table of Contents

7.1.3.1. Secure Initialization Overview

Secure initialization allows the device to boot and configure in a secured state.

Secure initialization begins with the CSS module. On FPGA power-up, the Configuration Subsystem (CSS) powers, initializes and loads the fuse bits. The CSS sends the FPGA its fuse configuration information. If the HPS is powered, the CSS sends the HPS fuse information to the Security Manager. This information is held in the HPS_fusesec shadow register in the Security Manager.

When the Security Manager is released from reset, it requests configuration information from the CSS and performs security checks. At this point, the rest of the HPS is still in reset. The security checks validate whether the state of each security option is valid. The Security Manager decodes the fuse bits and brings the rest of the HPS out of reset.

If there are errors in the initial transmission of the secure fuse information, the HPS stays in reset and no automatic retry occurs. Only an FPGA re-configuration causes a retry.

When the HPS is released from reset, the Security Manager sends signals to initialize the system blocks, such as the Clock Manager, FPGA Manager, System Manager. The clock control fuse information is automatically sent to the Clock Manager, the memory control fuse information is automatically sent to the Reset Manager and all other fuse functions (authentication, encryption, and public key source and length) are stored in a memory-mapped location for the boot ROM code to read. After these tasks are successfully completed, CPU0 comes out of reset in a secure state.

After CPU0 is released from reset, the boot ROM begins executing. At this time, the HPS is in a trusted state and the boot ROM code is guaranteed to execute as expected. For both secure and non-secure boot, all slave peripherals are brought out of reset in a secure state.

After initial security controls have been set, the boot ROM determines the second-stage boot loader source from the bootinfo register in the System Manager. The boot source can be from external memory through the HPS or through the FPGA. If the second-stage boot loader code comes from HPS external memory, then the boot ROM configures the clock and the interface to external memory.

When the boot ROM attempts to read from the flash, it looks for one of four images in external memory. Initially, it looks for image 0. If it is found, the image is authenticated, decrypted, or both depending on the requirements of the current security state. If these steps are successful, then the image is executed. However, if any of these steps fail, then the boot ROM moves onto the next image until it runs out of images.

For example, during a secure boot, the second-stage boot loader header includes an authentication key and the incoming image is authenticated. If indicated from the current security state, the image may be decrypted as well. The boot ROM contains functions to establish transitive trust to the second-stage boot code loaded from external flash or from the FPGA into on-chip RAM. If trust cannot be established in a secure boot, the HPS does not come out of reset and can attempt to load a different second-stage boot image.

For comprehensive information on the booting and boot image partitioning refer to the Booting and Configuration appendix of the Arria 10 Hard Processor Technical Reference Manual.

If all the images fail, it attempts to locate an image from the FPGA fabric and boot from there. If the FPGA boot fails, then it halts.

If the HPS receives its second-stage boot loader code from the FPGA, it waits for the FPGA to finish configuration before it obtains the image from FPGA RAM.

If required, a portion of the second-stage boot loader header can be used to raise security states of security features in the device that are currently in non-secure mode.