RFC: ESR_I/DLK processing

[Kumar Gala]

On Oct 28, 2011, at 3:43 PM, Jimi Xenidis wrote:

> arch/powerpc/kernel/head_fsl_booke.S has the following code:
>> 	/* Data Storage Interrupt */
>> 	START_EXCEPTION(DataStorage)
>> 	NORMAL_EXCEPTION_PROLOG
>> 	mfspr	r5,SPRN_ESR		/* Grab the ESR, save it, pass arg3 */
>> 	stw	r5,_ESR(r11)
>> 	mfspr	r4,SPRN_DEAR		/* Grab the DEAR, save it, pass arg2 */
>> 	andis.	r10,r5,(ESR_ILK|ESR_DLK)@h
>> 	bne	1f
>> 	EXC_XFER_EE_LITE(0x0300, handle_page_fault)
>> 1:
>> 	addi	r3,r1,STACK_FRAME_OVERHEAD
>> 	EXC_XFER_EE_LITE(0x0300, CacheLockingException)
> 
> 
> I need something similar for A2 (and all book3e) and was wondering, why this isn't just:
> 
>> diff --git a/arch/powerpc/mm/fault.c b/arch/powerpc/mm/fault.c
>> index 88abe70..8451822 100644
>> --- a/arch/powerpc/mm/fault.c
>> +++ b/arch/powerpc/mm/fault.c
>> @@ -159,6 +159,14 @@ int __kprobes do_page_fault(struct pt_regs *regs, unsigned long address,
>> 	}
>> #endif
>> 
>> +#ifdef CONFIG_PPC_BOOK3E
>> +	if (error_code & (ESR_DLK|ESR_ILK)) {
>> +		/* detect that this is a privileged op and SIGILL */
>> +		_exception(SIGILL, regs, ILL_PRVOPC, regs->nip);
>> +		return 0;
>> +	}
>> +#endif
>> +
>> 	if (notify_page_fault(regs))
>> 		return 0;
> 
> Its not like this need to be fast or anything.
> I'd be happy to submit a patch that adds to fault.c and removed the I/DLK processing from head_fsl_booke.S
> 
> Thoughts?
> -jx

Probably because at one point in time DSI had a fast path handling for us.  I've got no issues w/the proposed patch, just remember to mixup the CONFIG_PPC_BOOK3E as we don't define that in 32-bit fsl-booke 

- k