> -----Original Message-----
> From: Wood Scott-B07421
> Sent: Monday, July 02, 2012 12:25 PM
> To: Alexander Graf
> Cc: Yoder Stuart-B08248; kvm-ppc@xxxxxxxxxxxxxxx; kvm@xxxxxxxxxxxxxxx; Tabi Timur-B04825
> Subject: Re: [PATCH v11 8/8] PPC: Don't use hardcoded opcode for ePAPR hcall invocation
>
> On 07/02/2012 12:17 PM, Alexander Graf wrote:
> >
> > On 02.07.2012, at 19:16, Scott Wood wrote:
> >
> >> 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@xxxxxxxxxxxxx>
> >>>>>>
> >>>>>> Signed-off-by: Liu Yu <yu.liu@xxxxxxxxxxxxx>
> >>>>>> Signed-off-by: Stuart Yoder <stuart.yoder@xxxxxxxxxxxxx>
> >>>>>> ---
> >>>>>> -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.
> >
> > Only after the change, not before it.
>
> Hmm. The comment says, "XER, CTR, and LR are currently listed as
> clobbers because it's uncertain whether they will be clobbered." Maybe
> it dates back to when the ABI was still being discussed? Timur, do you
> recall?
>
> In any case, LR is nonvolatile in the spec and in the implementations I
> know about (KVM and Topaz).
Based on this thread I am going to leave this patch as is.
Stuart
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