hujun260 opened a new pull request, #17967:
URL: https://github.com/apache/nuttx/pull/17967
## Summary
Make ARM64 MPU region tracking SMP-aware by converting the global
g_mpu_region variable into a per-CPU array. This ensures that each CPU core
independently tracks its allocated MPU regions, preventing cross-CPU region
conflicts in multi-core systems. The change replaces all accesses to
g_mpu_region with g_mpu_region[this_cpu()], enabling proper resource management
in SMP configurations.
## Changes
- **arch/arm64/src/common/arm64_mpu.c**:
- Line 76: Change `static unsigned int g_mpu_region` to `static unsigned
int g_mpu_region[CONFIG_SMP_NCPUS]`
- Line 156: Update region allocation to use `g_mpu_region[this_cpu()]` in
ffs() call
- Line 161: Update region bit-set to use `g_mpu_region[this_cpu()]`
- Line 194: Update region bit-clear to use `g_mpu_region[this_cpu()]`
- Line 278: Update region validity check to use `g_mpu_region[this_cpu()]`
- All changes consistently index the array with this_cpu() for per-CPU
tracking
## Benefits & Technical Details
- **Per-CPU tracking**: Each CPU core maintains independent MPU region
allocation bitmap
- **SMP correctness**: Prevents race conditions where different CPUs
interfere with each other's region tracking
- **Isolation**: MPU regions allocated on one CPU don't affect region
availability on other CPUs
- **Scalability**: Enables proper MPU configuration for each CPU in
multi-core systems
- **Memory protection**: Each core can independently manage its memory
protection regions
## Testing
- Verified each CPU core independently tracks its allocated MPU regions
- Confirmed no cross-CPU interference in region allocation and deallocation
- Tested simultaneous MPU region allocation on multiple CPUs
- Validated region modification operations on per-CPU regions
- Confirmed SMP systems properly isolate MPU configuration per core
## Impact
- **Correctness**: Fixes MPU region tracking for multi-core ARM64 systems
- **Compatibility**: No impact on single-CPU configurations (array size 1)
- **Architecture**: ARM64 specific MPU management improvement
- **Scope**: Affects all ARM64 MPU region allocation, deallocation, and
modification operations
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