Subject: Re: [PATCH 1/4] powerpc/perf: Convert mmcra_sipr/sihv() to regs_sipr/sihv()

From: Sukadev Bhattiprolu <[email-masked]>
Date: Thu, 25 Apr 2013 10:11:33 -0700

Michael Ellerman [[email-masked]] wrote:
| From: Michael Ellerman <[email-masked]>
| 
| On power8 the SIPR and SIHV are not in MMCRA, so convert the routines
| to take regs and change the names accordingly.
| 
| Signed-off-by: Michael Ellerman <[email-masked]>
| ---
|  arch/powerpc/perf/core-book3s.c |   20 +++++++++++---------
|  1 file changed, 11 insertions(+), 9 deletions(-)
| 
| diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
| index fcfafa0..cb1618d 100644
| --- a/arch/powerpc/perf/core-book3s.c
| +++ b/arch/powerpc/perf/core-book3s.c
| @@ -112,24 +112,24 @@ static inline void perf_get_data_addr(struct pt_regs *regs, u64 *addrp)
|  		*addrp = mfspr(SPRN_SDAR);
|  }
| 
| -static bool mmcra_sihv(unsigned long mmcra)
| +static bool regs_sihv(struct pt_regs *regs)
|  {
|  	unsigned long sihv = MMCRA_SIHV;
| 
|  	if (ppmu->flags & PPMU_ALT_SIPR)
|  		sihv = POWER6_MMCRA_SIHV;
| 
| -	return !!(mmcra & sihv);
| +	return !!(regs->dsisr & sihv);
|  }
| 
| -static bool mmcra_sipr(unsigned long mmcra)
| +static bool regs_sipr(struct pt_regs *regs)
|  {
|  	unsigned long sipr = MMCRA_SIPR;
| 

Would it make sense to add this here:

	if (ppmu->flags & PPMU_NO_SIPR)
		return 0;
so ....

|  	if (ppmu->flags & PPMU_ALT_SIPR)
|  		sipr = POWER6_MMCRA_SIPR;
| 
| -	return !!(mmcra & sipr);
| +	return !!(regs->dsisr & sipr);
|  }
| 
|  static inline u32 perf_flags_from_msr(struct pt_regs *regs)
| @@ -143,7 +143,6 @@ static inline u32 perf_flags_from_msr(struct pt_regs *regs)
| 
|  static inline u32 perf_get_misc_flags(struct pt_regs *regs)
|  {
| -	unsigned long mmcra = regs->dsisr;
|  	unsigned long use_siar = regs->result;
| 
|  	if (!use_siar)
| @@ -163,10 +162,12 @@ static inline u32 perf_get_misc_flags(struct pt_regs *regs)
|  	}
| 
|  	/* PR has priority over HV, so order below is important */
| -	if (mmcra_sipr(mmcra))
| +	if (regs_sipr(regs))
|  		return PERF_RECORD_MISC_USER;
| -	if (mmcra_sihv(mmcra) && (freeze_events_kernel != MMCR0_FCHV))
| +
| +	if (regs_sihv(regs) && (freeze_events_kernel != MMCR0_FCHV))
|  		return PERF_RECORD_MISC_HYPERVISOR;
| +
|  	return PERF_RECORD_MISC_KERNEL;
|  }
| 
| @@ -182,6 +183,8 @@ static inline void perf_read_regs(struct pt_regs *regs)
|  	int marked = mmcra & MMCRA_SAMPLE_ENABLE;
|  	int use_siar;
| 
| +	regs->dsisr = mmcra;
| +
|  	/*
|  	 * If this isn't a PMU exception (eg a software event) the SIAR is
|  	 * not valid. Use pt_regs.
| @@ -205,12 +208,11 @@ static inline void perf_read_regs(struct pt_regs *regs)
|  		use_siar = 1;
|  	else if ((ppmu->flags & PPMU_NO_CONT_SAMPLING))
|  		use_siar = 0;
| -	else if (!(ppmu->flags & PPMU_NO_SIPR) && mmcra_sipr(mmcra))
| +	else if (!(ppmu->flags & PPMU_NO_SIPR) && regs_sipr(regs))

... this becomes

	else if (regs_sipr(regs))

mmcra_sipr() is used currently in two places and both places check
the NO_SIPR flag.

The reason is that this line gets modified in PATCH 3/4 to:

	else if (!regs_no_sipr(regs) && regs_sipr(regs))

which is kind of hard to read. if (!not_X && X)

Sukadev