Re: [RFC V2 7/8] powerpc: Enable IRQ generic entry/exit path.

Shrikanth Hegde
2025-09-16T04:18:04Z

On 9/9/25 2:32 AM, Mukesh Kumar Chaurasiya wrote:
> Enable generic entry/exit path for ppc irq.
>
> Signed-off-by: Mukesh Kumar Chaurasiya <mchauras@linux.ibm.com>
> ---
> arch/powerpc/Kconfig | 1 +
> arch/powerpc/include/asm/entry-common.h | 93 ++---
> arch/powerpc/include/asm/interrupt.h | 492 +++---------------------
> arch/powerpc/kernel/interrupt.c | 9 +-
> arch/powerpc/kernel/interrupt_64.S | 2 -
> 5 files changed, 92 insertions(+), 505 deletions(-)
>
\
> diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c
> index f53d432f60870..7bb8a31b24ea7 100644
> --- a/arch/powerpc/kernel/interrupt.c
> +++ b/arch/powerpc/kernel/interrupt.c
> @@ -297,13 +297,8 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs)
> /* Returning to a kernel context with local irqs enabled. */
> WARN_ON_ONCE(!(regs->msr & MSR_EE));
> again:
> - if (need_irq_preemption()) {
> - /* Return to preemptible kernel context */
> - if (unlikely(read_thread_flags() & _TIF_NEED_RESCHED)) {
> - if (preempt_count() == 0)
> - preempt_schedule_irq();
> - }
> - }
> + if (need_irq_preemption())
> + irqentry_exit_cond_resched();

irqentry_exit_cond_resched is also called in irqentry_exit. It would be
better if we can find ways to avoid calling it again.

I see a loop here. But comment says it is not enabling irq again. so the
loop is bounded. So might be okay to remove cond_resched here. do run
preemptirq, irq tracers to ensure that is case.

Also, what is this "soft_interrupts"?

>
> check_return_regs_valid(regs);
>
> diff --git a/arch/powerpc/kernel/interrupt_64.S b/arch/powerpc/kernel/interrupt_64.S
> index 1ad059a9e2fef..6aa88fe91fb6a 100644
> --- a/arch/powerpc/kernel/interrupt_64.S
> +++ b/arch/powerpc/kernel/interrupt_64.S
> @@ -418,8 +418,6 @@ _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\())
> beq interrupt_return_\srr\()_kernel
> interrupt_return_\srr\()_user: /* make backtraces match the _kernel variant */
> _ASM_NOKPROBE_SYMBOL(interrupt_return_\srr\()_user)
> - addi r3,r1,STACK_INT_FRAME_REGS
> - bl CFUNC(interrupt_exit_user_prepare)
> #ifndef CONFIG_INTERRUPT_SANITIZE_REGISTERS
> cmpdi r3,0
> bne- .Lrestore_nvgprs_\srr