[PATCH] powerpc/perf: use MSR to report privilege level on P9 DD1

[Madhavan Srinivasan]

On Tuesday 17 January 2017 11:16 AM, Michael Ellerman wrote:
> Madhavan Srinivasan <maddy at linux.vnet.ibm.com> writes:
>
>> "use_siar" variable is primarily used for deciding the sampled address
>> and the privilege level to be reported for a sample. perf_read_regs()
>> function updates the "use_siar" and "regs->result" based on the pmu
>> flags along with other checks. To force the use of MSR to report the
>> privilege level and to use "regs->nip" to report the instruction pointer,
>> set "PPMU_NO_CONT_SAMPLING" flag and remove "PPMU_HAS_SIER" from the
>> ppmu->flags.
> This still won't work for marked events AFAICS:

nice catch. My bad. Did not try with the marked events when testing this
patch.

>
> 	if (TRAP(regs) != 0xf00)
> 		use_siar = 0;
> 	else if (marked)
> 		use_siar = 1;
> 	else if ((ppmu->flags & PPMU_NO_CONT_SAMPLING))
> 		use_siar = 0;
> 	else if (!(ppmu->flags & PPMU_NO_SIPR) && regs_sipr(regs))
> 		use_siar = 0;
> 	else
> 		use_siar = 1;
>
> So perhaps we just want a USE_SIAR flag?
OK, Will add a new flag. How about "PPMU_DISBALE_USE_SIAR"?

> And I don't see how HAS_SIER is related? Or is SIER broken too?

We dont see proper values in SIER for some samples and we use
SIER (regs_sipr) to update the misc_flag.

Will fix the commit message.

Maddy

> cheers
>