[PATCH v2 0/8] Generic IRQ entry/exit support for powerpc

[Samir M]

On 14/12/25 6:32 pm, Mukesh Kumar Chaurasiya wrote:
> Adding support for the generic irq entry/exit handling for PowerPC. The
> goal is to bring PowerPC in line with other architectures that already
> use the common irq entry infrastructure, reducing duplicated code and
> making it easier to share future changes in entry/exit paths.
>
> This is slightly tested of ppc64le and ppc32.
>
> The performance benchmarks are below:
>
> perf bench syscall usec/op
>
> | Test            | With Patch | Without Patch | % Change |
> | --------------- | ---------- | ------------- | -------- |
> | getppid usec/op | 0.207795   | 0.210373      | -1.22%   |
> | getpgid usec/op | 0.206282   | 0.211676      | -2.55%   |
> | fork usec/op    | 833.986    | 814.809       | +2.35%   |
> | execve usec/op  | 360.939    | 365.168       | -1.16%   |
>
>
> perf bench syscall ops/sec
>
> | Test            | With Patch | Without Patch | % Change |
> | --------------- | ---------- | ------------- | -------- |
> | getppid ops/sec | 48,12,433  | 47,53,459     | +1.24%   |
> | getpgid ops/sec | 48,47,744  | 47,24,192     | +2.61%   |
> | fork ops/sec    | 1,199      | 1,227         | -2.28%   |
> | execve ops/sec  | 2,770      | 2,738         | +1.16%   |
>
> IPI latency benchmark
>
> | Metric                  | With Patch       | Without Patch    | % Change |
> | ----------------------- | ---------------- | ---------------- | -------- |
> | Dry-run (ns)            | 206,675.81       | 206,719.36       | -0.02%   |
> | Self-IPI avg (ns)       | 1,939,991.00     | 1,976,116.15     | -1.83%   |
> | Self-IPI max (ns)       | 3,533,718.93     | 3,582,650.33     | -1.37%   |
> | Normal IPI avg (ns)     | 111,110,034.23   | 110,513,373.51   | +0.54%   |
> | Normal IPI max (ns)     | 150,393,442.64   | 149,669,477.89   | +0.48%   |
> | Broadcast IPI max (ns)  | 3,978,231,022.96 | 4,359,916,859.46 | -8.73%   |
> | Broadcast lock max (ns) | 4,025,425,714.49 | 4,384,956,730.83 | -8.20%   |
>
> Thats very close to performance earlier with arch specific handling.
>
> Tests done:
>   - Build and boot on ppc64le pseries.
>   - Build and boot on ppc64le powernv8 powernv9 powernv10.
>   - Build and boot on ppc32.
>   - Performance benchmark done with perf syscall basic on pseries.
>
> Changelog:
>
> V1 -> V2
>   - Fix an issue where context tracking was showing warnings for
>     incorrect context
> V1: https://lore.kernel.org/all/20251102115358.1744304-1-mkchauras@linux.ibm.com/
>
> RFC -> PATCH V1
>   - Fix for ppc32 spitting out kuap lock warnings.
>   - ppc64le powernv8 crash fix.
>   - Review comments incorporated from previous RFC.
> RFC https://lore.kernel.org/all/20250908210235.137300-2-mchauras@linux.ibm.com/
>
> Mukesh Kumar Chaurasiya (8):
>    powerpc: rename arch_irq_disabled_regs
>    powerpc: Prepare to build with generic entry/exit framework
>    powerpc: introduce arch_enter_from_user_mode
>    powerpc: Introduce syscall exit arch functions
>    powerpc: add exit_flags field in pt_regs
>    powerpc: Prepare for IRQ entry exit
>    powerpc: Enable IRQ generic entry/exit path.
>    powerpc: Enable Generic Entry/Exit for syscalls.
>
>   arch/powerpc/Kconfig                    |   2 +
>   arch/powerpc/include/asm/entry-common.h | 536 ++++++++++++++++++++++++
>   arch/powerpc/include/asm/hw_irq.h       |   4 +-
>   arch/powerpc/include/asm/interrupt.h    | 401 +++---------------
>   arch/powerpc/include/asm/ptrace.h       |   3 +
>   arch/powerpc/include/asm/stacktrace.h   |   6 +
>   arch/powerpc/include/asm/syscall.h      |   5 +
>   arch/powerpc/include/asm/thread_info.h  |   1 +
>   arch/powerpc/include/uapi/asm/ptrace.h  |  14 +-
>   arch/powerpc/kernel/asm-offsets.c       |   1 +
>   arch/powerpc/kernel/interrupt.c         | 255 ++---------
>   arch/powerpc/kernel/ptrace/ptrace.c     | 142 +------
>   arch/powerpc/kernel/signal.c            |   8 +
>   arch/powerpc/kernel/syscall.c           | 119 +-----
>   arch/powerpc/kernel/traps.c             |   2 +-
>   arch/powerpc/kernel/watchdog.c          |   2 +-
>   arch/powerpc/perf/core-book3s.c         |   2 +-
>   17 files changed, 685 insertions(+), 818 deletions(-)
>   create mode 100644 arch/powerpc/include/asm/entry-common.h

Hi,


I have reviewed and tested the generic IRQ entry/exist patch series. 
Below are my observations:

Test Coverage
Successfully ran LTP (specially syscall) and entire LTP test suite, 
without observing any regressions or issues related to the implementation.
Successfully ran kernel self test and no regressions are observed.

System Configuration
• CPUs: 80
• Kernel: 6.19.0-rc1
• Processor mode: Dedicated


Performance Evaluation
• Conducted bench marking using "perf bench syscall usec/ops".
• No functional regressions observed, and results were consistent with 
expectations.

| Test                   |  With Patch   | Without Patch  | % Change |
| -------------  |  —————   | ——————    | -------- |
| getppid ops/sec | 9,901,942    | 10,066,131     | -1.63%     |
| getpgid ops/sec | 9,886,533    | 9,978,781       | -0.92%     |
| fork ops/sec       | 2,571           | 2,601             | -1.15%    |
| execve ops/sec   | 2,567           | 2,542             | +0.98% |


Please add below tag:

Tested-by: Samir M <samir at linux.ibm.com>


Thanks,

Samir