ARM Cortex-A SVC Handler IRQ Masking Behavior When working with ARM Cortex-A series processors, particularly in systems where Supervisor Calls (SVC) are used to transition from EL0 (user mode) to EL1 (kernel mode), understanding the interaction between exception handling and interrupt masking is critical. A common issue arises when an SVC handler fails to properly…
ARM Virtualization in Mobile: Beyond Single OS Assumptions The assumption that mobile devices run only one operating system at a time is a common misconception. While it is true that most mobile devices are designed to operate under a single primary OS, such as Android or iOS, the need for virtualization support in ARM-based mobile…
Understanding DEFLAGS and FPSCR Exception Flag Monitoring on Cortex-A9 The Cortex-A9 Floating Point Unit (FPU) is a critical component for handling floating-point operations in ARM-based systems. One of its key features is the Floating-Point Status and Control Register (FPSCR), which includes exception flags that indicate the occurrence of specific floating-point exceptions such as invalid operation,…
GICD_IERRR Bit Set During Bootup: SPI RAM Errors and System Initialization The GICD_IERRR (Interrupt Error Reporting Register) bit being set during system bootup is a critical issue that can indicate underlying problems in the ARM CoreLink GIC-600 Generic Interrupt Controller. The GICD_IERRR register is designed to report errors related to the RAM used for Shared…
GICv3 System Register Access vs GICv2 Memory-Mapped Interface Performance The transition from GICv2 to GICv3 introduced significant architectural changes, particularly in how the CPU interfaces with the Generic Interrupt Controller (GIC). One of the most notable changes is the shift from a memory-mapped interface in GICv2 to a system register-based interface in GICv3. This change…
ARM Cortex-M4 AHB Bus Matrix Arbitration and DMA Timing Errors The ARM Cortex-M4 microcontroller, like many ARM-based systems, utilizes the Advanced High-performance Bus (AHB) for communication between masters (such as the CPU and DMA controller) and slaves (such as ROM, SRAM, and SDRAM). The AHB Bus Matrix is a critical component that manages access to…
ARM Cortex-A53 Stage-2 MMU Misconfiguration Leading to Memory Corruption The core issue revolves around memory corruption observed after switching from Exception Level 2 (EL2) to Exception Level 1 (EL1) on an ARM Cortex-A53 processor. The system is configured with a Stage-2 Memory Management Unit (MMU) using a 64KB granule and 512MB block mappings. The Intermediate…
Core 1 MMU Configuration by Core 0 in a Dual A53 Cluster The ARM Cortex-A53 processor is a widely used 64-bit core in embedded systems, known for its power efficiency and performance. In a dual-core A53 cluster, each core operates independently, but they share resources such as the L2 cache and the AXI master interface….
GIC Distributor Register Write Latency and Visibility Guarantees The ARM Generic Interrupt Controller (GIC) is a critical component in ARM-based systems, responsible for managing interrupts across multiple cores and peripherals. One of the key aspects of the GIC architecture is the GIC Distributor, which handles the routing and prioritization of interrupts. When developing systems that…
ARM PMCCNTR_EL0 Access Trapping in KVM Guest Virtual Machines Accessing the ARM Performance Monitors Cycle Count Register (PMCCNTR_EL0) directly from a KVM-based guest virtual machine (VM) can be a challenging task due to the trapping mechanism enforced by the hypervisor at Exception Level 2 (EL2). The PMCCNTR_EL0 register is a critical component for performance monitoring,…