Re: [PATCH v11 8/8] PPC: Don't use hardcoded opcode for ePAPR hcall invocation

[Scott Wood <scottwood@freescale.com>]

On 07/02/2012 12:13 PM, Alexander Graf wrote:
> 
> On 02.07.2012, at 19:10, Scott Wood wrote:
> 
>> On 07/02/2012 07:30 AM, Alexander Graf wrote:
>>>
>>> On 22.06.2012, at 22:06, Stuart Yoder wrote:
>>>
>>>> From: Liu Yu-B13201 <Yu.Liu@freescale.com>
>>>>
>>>> Signed-off-by: Liu Yu <yu.liu@freescale.com>
>>>> Signed-off-by: Stuart Yoder <stuart.yoder@freescale.com>
>>>> ---
>>>> -v11: no changes
>>>>
>>>> arch/powerpc/include/asm/epapr_hcalls.h |   22 +++++++++---------
>>>> arch/powerpc/include/asm/fsl_hcalls.h   |   36 +++++++++++++++---------------
>>>> 2 files changed, 29 insertions(+), 29 deletions(-)
>>>>
>>>> diff --git a/arch/powerpc/include/asm/epapr_hcalls.h b/arch/powerpc/include/asm/epapr_hcalls.h
>>>> index 833ce2c..b8d9445 100644
>>>> --- a/arch/powerpc/include/asm/epapr_hcalls.h
>>>> +++ b/arch/powerpc/include/asm/epapr_hcalls.h
>>>> @@ -195,7 +195,7 @@ static inline unsigned int ev_int_set_config(unsigned int interrupt,
>>>> 	r5  = priority;
>>>> 	r6  = destination;
>>>>
>>>> -	__asm__ __volatile__ ("sc 1"
>>>> +	asm volatile("bl	epapr_hypercall_start"
>>>> 		: "+r" (r11), "+r" (r3), "+r" (r4), "+r" (r5), "+r" (r6)
>>>> 		: : EV_HCALL_CLOBBERS4
>>>
>>> Hrm. ePAPR hypercalls are allowed to clobber lr, right? But our hypercall entry code depends on lr staying alive:
>>
>> ePAPR 1.1 says LR is nonvolatile.
> 
> Why is it in the clobber list then? 

Because the inline assembly code is clobbering it -- not the hv-provided
hcall instructions.

-Scott