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During context switching from higher EL (EL2 or higher) to lower EL can cause incorrect translation in TLB due to speculative execution of AT instruction using out-of-context translation regime. Workaround is implemented as below during EL's (EL1 or EL2) "context_restore" operation: 1. Disable page table walk using SCTLR.M and TCR.EPD0 & EPD1 bits for EL1 or EL2 (stage1 and stage2 disabled) 2. Save all system registers except TCR and SCTLR (for EL1 and EL2) 3. Do memory barrier operation (isb) to ensure all system register writes are done. 4. Restore TCR and SCTLR registers (for EL1 and EL2) Errata details are available for various CPUs as below: Cortex-A76: 1165522 Cortex-A72: 1319367 Cortex-A57: 1319537 Cortex-A55: 1530923 Cortex-A53: 1530924 More details can be found in mail-chain: https://lists.trustedfirmware.org/pipermail/tf-a/2020-April/000445.html Currently, Workaround is implemented as build option which is default disabled. Signed-off-by: Manish V Badarkhe <Manish.Badarkhe@arm.com> Change-Id: If8545e61f782cb0c2dda7ffbaf50681c825bd2f0 |
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Trusted Firmware-A ================== Trusted Firmware-A (TF-A) is a reference implementation of secure world software for `Arm A-Profile architectures`_ (Armv8-A and Armv7-A), including an Exception Level 3 (EL3) `Secure Monitor`_. It provides a suitable starting point for productization of secure world boot and runtime firmware, in either the AArch32 or AArch64 execution states. TF-A implements Arm interface standards, including: - `Power State Coordination Interface (PSCI)`_ - `Trusted Board Boot Requirements CLIENT (TBBR-CLIENT)`_ - `SMC Calling Convention`_ - `System Control and Management Interface (SCMI)`_ - `Software Delegated Exception Interface (SDEI)`_ The code is designed to be portable and reusable across hardware platforms and software models that are based on the Armv8-A and Armv7-A architectures. In collaboration with interested parties, we will continue to enhance TF-A with reference implementations of Arm standards to benefit developers working with Armv7-A and Armv8-A TrustZone technology. Users are encouraged to do their own security validation, including penetration testing, on any secure world code derived from TF-A. More Info and Documentation --------------------------- To find out more about Trusted Firmware-A, please `view the full documentation`_ that is available through `trustedfirmware.org`_. -------------- *Copyright (c) 2013-2019, Arm Limited and Contributors. All rights reserved.* .. _Armv7-A and Armv8-A: https://developer.arm.com/products/architecture/a-profile .. _Secure Monitor: http://www.arm.com/products/processors/technologies/trustzone/tee-smc.php .. _Power State Coordination Interface (PSCI): PSCI_ .. _PSCI: http://infocenter.arm.com/help/topic/com.arm.doc.den0022d/Power_State_Coordination_Interface_PDD_v1_1_DEN0022D.pdf .. _Trusted Board Boot Requirements CLIENT (TBBR-CLIENT): https://developer.arm.com/docs/den0006/latest/trusted-board-boot-requirements-client-tbbr-client-armv8-a .. _SMC Calling Convention: http://infocenter.arm.com/help/topic/com.arm.doc.den0028b/ARM_DEN0028B_SMC_Calling_Convention.pdf .. _System Control and Management Interface (SCMI): SCMI_ .. _SCMI: http://infocenter.arm.com/help/topic/com.arm.doc.den0056a/DEN0056A_System_Control_and_Management_Interface.pdf .. _Software Delegated Exception Interface (SDEI): SDEI_ .. _SDEI: http://infocenter.arm.com/help/topic/com.arm.doc.den0054a/ARM_DEN0054A_Software_Delegated_Exception_Interface.pdf .. _Arm A-Profile architectures: https://developer.arm.com/architectures/cpu-architecture/a-profile .. _view the full documentation: https://www.trustedfirmware.org/docs/tf-a .. _trustedfirmware.org: http://www.trustedfirmware.org