ARM Paravirtualization Support

Files
file	cpukit/score/cpu/arm/include/rtems/score/paravirt.h
	This header file provides definitions pertaining to paravirtualization of the ARM port.

Macros
#define	ARM_DISABLE_INLINE_ISR_DISABLE_ENABLE
#define	ARM_DISABLE_THREAD_ID_REGISTER_USE

Detailed Description

This handler encapulates the functionality (primarily conditional feature defines) related to paravirtualization on the ARM.

Paravirtualization on the ARM makes the following assumptions:

• RTEMS executes in user space
• Interrupt enable/disable support using the MSR must be disabled and replaced with BSP provided methods which are adapted to the hosting environment.

Macro Definition Documentation

ARM_DISABLE_INLINE_ISR_DISABLE_ENABLE

#define ARM_DISABLE_INLINE_ISR_DISABLE_ENABLE

In a paravirtualized environment, RTEMS executes in user space and cannot disable/enable external exceptions (e.g. interrupts). The BSP which acts as an adapter to the hosting environment will provide the interrupt enable/disable methods.

ARM_DISABLE_THREAD_ID_REGISTER_USE

#define ARM_DISABLE_THREAD_ID_REGISTER_USE

In a paravirtualized environment, RTEMS executes in user space and cannot write to the the Thread ID register which is normally used. CP15 C13 has three variants of a Thread ID register.

• Opcode_2 = 2: This register is both user and privileged R/W accessible.
• Opcode_2 = 3: This register is user read-only and privileged R/W accessible.
• Opcode_2 = 4: This register is privileged R/W accessible only.