Excerpts from Christophe Leroy's message of August 4, 2021 3:27 pm: > 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>
Probably okay to do now things are ironing out. Unless we want to make a new define for interrupt handler debug and put a bunch of these asserts under it. There's quite a lot more here, and in asm/interrupt.h, etc. Thanks, Nick > --- > 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 > >
