[RFC PATCH 02/12] powerpc: remove arguments from interrupt handler functions

[Nicholas Piggin]

Excerpts from Christophe Leroy's message of September 7, 2020 9:34 pm:
> On Mon, 2020-09-07 at 11:20 +0200, Christophe Leroy wrote:
>> 
>> Le 05/09/2020 à 19:43, Nicholas Piggin a écrit :
>> > Make interrupt handlers all just take the pt_regs * argument and load
>> > DAR/DSISR etc from that. Make those that return a value return long.
>> 
>> I like this, it will likely simplify a bit the VMAP_STACK mess.
>> 
>> Not sure it is that easy. My board is stuck after the start of init.
>> 
>> 
>> On the 8xx, on Instruction TLB Error exception, we do
>> 
>> 	andis.	r5,r9,DSISR_SRR1_MATCH_32S at h /* Filter relevant SRR1 bits */
>> 
>> On book3s/32, on ISI exception we do:
>> 	andis.	r5,r9,DSISR_SRR1_MATCH_32S at h /* Filter relevant SRR1 bits */
>> 
>> On 40x and bookE, on ISI exception we do:
>> 	li	r5,0			/* Pass zero as arg3 */
>> 
>> 
>> And regs->dsisr will just contain nothing
>> 
>> So it means we should at least write back r5 into regs->dsisr from there 
>> ? The performance impact should be minimal as we already write _DAR so 
>> the cache line should already be in the cache.
>> 
>> A hacky 'stw r5, _DSISR(r1)' in handle_page_fault() does the trick, 
>> allthough we don't want to do it for both ISI and DSI at the end, so 
>> you'll have to do it in every head_xxx.S
> 
> To get you series build and work, I did the following hacks:

Great, thanks for this.

> diff --git a/arch/powerpc/include/asm/interrupt.h
> b/arch/powerpc/include/asm/interrupt.h
> index acfcc7d5779b..c11045d3113a 100644
> --- a/arch/powerpc/include/asm/interrupt.h
> +++ b/arch/powerpc/include/asm/interrupt.h
> @@ -93,7 +93,9 @@ static inline void interrupt_nmi_exit_prepare(struct
> pt_regs *regs, struct inter
>  {
>  	nmi_exit();
>  
> +#ifdef CONFIG_PPC64
>  	this_cpu_set_ftrace_enabled(state->ftrace_enabled);
> +#endif

This seems okay, not a hack.

>  #ifdef CONFIG_PPC_BOOK3S_64
>  	/* Check we didn't change the pending interrupt mask. */
> diff --git a/arch/powerpc/kernel/entry_32.S
> b/arch/powerpc/kernel/entry_32.S
> index f4d0af8e1136..66f7adbe1076 100644
> --- a/arch/powerpc/kernel/entry_32.S
> +++ b/arch/powerpc/kernel/entry_32.S
> @@ -663,6 +663,7 @@ ppc_swapcontext:
>   */
>  	.globl	handle_page_fault
>  handle_page_fault:
> +	stw	r5,_DSISR(r1)
>  	addi	r3,r1,STACK_FRAME_OVERHEAD
>  #ifdef CONFIG_PPC_BOOK3S_32
>  	andis.  r0,r5,DSISR_DABRMATCH at h

Is this what you want to do for 32, or do you want to seperate
ISI and DSI sides?

Thanks,
Nick