In those hot functions that are called at every interrupt, any saved cycle is worth it.
interrupt_exit_user_prepare() and interrupt_exit_kernel_prepare() are called from three places: - From entry_32.S - From interrupt_64.S - From interrupt_exit_user_restart() and interrupt_exit_kernel_restart() In entry_32.S, there are inambiguously called based on MSR_PR: interrupt_return: lwz r4,_MSR(r1) addi r3,r1,STACK_FRAME_OVERHEAD andi. r0,r4,MSR_PR beq .Lkernel_interrupt_return bl interrupt_exit_user_prepare ... .Lkernel_interrupt_return: bl interrupt_exit_kernel_prepare In interrupt_64.S, that's similar: interrupt_return_\srr\(): ld r4,_MSR(r1) andi. r0,r4,MSR_PR beq interrupt_return_\srr\()_kernel interrupt_return_\srr\()_user: /* make backtraces match the _kernel variant */ addi r3,r1,STACK_FRAME_OVERHEAD bl interrupt_exit_user_prepare ... interrupt_return_\srr\()_kernel: addi r3,r1,STACK_FRAME_OVERHEAD bl interrupt_exit_kernel_prepare In interrupt_exit_user_restart() and interrupt_exit_kernel_restart(), MSR_PR is verified respectively by BUG_ON(!user_mode(regs)) and BUG_ON(user_mode(regs)) prior to calling interrupt_exit_user_prepare() and interrupt_exit_kernel_prepare(). The verification in interrupt_exit_user_prepare() and interrupt_exit_kernel_prepare() are therefore useless and can be removed. Signed-off-by: Christophe Leroy <christophe.le...@csgroup.eu> Acked-by: Nicholas Piggin <npig...@gmail.com> --- arch/powerpc/kernel/interrupt.c | 2 -- 1 file changed, 2 deletions(-) diff --git a/arch/powerpc/kernel/interrupt.c b/arch/powerpc/kernel/interrupt.c index 21bbd615ca41..f26caf911ab5 100644 --- a/arch/powerpc/kernel/interrupt.c +++ b/arch/powerpc/kernel/interrupt.c @@ -465,7 +465,6 @@ notrace unsigned long interrupt_exit_user_prepare(struct pt_regs *regs) if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x)) BUG_ON(!(regs->msr & MSR_RI)); - BUG_ON(!(regs->msr & MSR_PR)); BUG_ON(arch_irq_disabled_regs(regs)); CT_WARN_ON(ct_state() == CONTEXT_USER); @@ -499,7 +498,6 @@ notrace unsigned long interrupt_exit_kernel_prepare(struct pt_regs *regs) if (!IS_ENABLED(CONFIG_BOOKE) && !IS_ENABLED(CONFIG_40x) && unlikely(!(regs->msr & MSR_RI))) unrecoverable_exception(regs); - BUG_ON(regs->msr & MSR_PR); /* * CT_WARN_ON comes here via program_check_exception, * so avoid recursion. -- 2.25.0