powerpc/perf: Sample only if SIAR-Valid bit is set in P7+
On POWER7+ two new bits (mmcra[35] and mmcra[36]) indicate whether the
contents of SIAR and SDAR are valid.
For marked instructions on P7+, we must save the contents of SIAR and
SDAR registers only if these new bits are set.
This code/check for the SIAR-Valid bit is specific to P7+, so rather than
waste a CPU-feature bit use the PVR flag.
Note that Carl Love proposed a similar change for oprofile:
https://lkml.org/lkml/2012/6/22/309
Changelog [v4]:
- Port to powerpc/next branch - where PV_POWER7p is now PVR_POWER7p
and __is_processor() is now pvr_version_is()
- Ensure patch doesn't break 32-bit build.
Changelog[v3]:
- Commit 5c093efa6f2 added checks to use SIAR only for kernel samples.
Extend that to use SIAR only if SIAR-valid bit is set (in processors
that implement that bit).
Changelog[v2]:
- [Gabriel Paubert] Rename PV_POWER7P to PV_POWER7p.
Signed-off-by: Sukadev Bhattiprolu <suka...@linux.vnet.ibm.com>
---
arch/powerpc/include/asm/perf_event_server.h | 1 +
arch/powerpc/include/asm/reg.h | 4 ++
arch/powerpc/perf/core-book3s.c | 44 ++++++++++++++++++++++---
arch/powerpc/perf/power7-pmu.c | 3 ++
4 files changed, 46 insertions(+), 6 deletions(-)
diff --git a/arch/powerpc/include/asm/perf_event_server.h
b/arch/powerpc/include/asm/perf_event_server.h
index 078019b..9710be3 100644
--- a/arch/powerpc/include/asm/perf_event_server.h
+++ b/arch/powerpc/include/asm/perf_event_server.h
@@ -49,6 +49,7 @@ struct power_pmu {
#define PPMU_ALT_SIPR 2 /* uses alternate posn for SIPR/HV */
#define PPMU_NO_SIPR 4 /* no SIPR/HV in MMCRA at all */
#define PPMU_NO_CONT_SAMPLING 8 /* no continuous sampling */
+#define PPMU_SIAR_VALID 16 /* Processor has SIAR Valid bit
*/
/*
* Values for flags to get_alternatives()
diff --git a/arch/powerpc/include/asm/reg.h b/arch/powerpc/include/asm/reg.h
index a1096fb..d24c141 100644
--- a/arch/powerpc/include/asm/reg.h
+++ b/arch/powerpc/include/asm/reg.h
@@ -606,6 +606,10 @@
#define POWER6_MMCRA_SIPR 0x0000020000000000ULL
#define POWER6_MMCRA_THRM 0x00000020UL
#define POWER6_MMCRA_OTHER 0x0000000EUL
+
+#define POWER7P_MMCRA_SIAR_VALID 0x10000000 /* P7+ SIAR contents valid */
+#define POWER7P_MMCRA_SDAR_VALID 0x08000000 /* P7+ SDAR contents valid */
+
#define SPRN_PMC1 787
#define SPRN_PMC2 788
#define SPRN_PMC3 789
diff --git a/arch/powerpc/perf/core-book3s.c b/arch/powerpc/perf/core-book3s.c
index fb55da9..0db88f5 100644
--- a/arch/powerpc/perf/core-book3s.c
+++ b/arch/powerpc/perf/core-book3s.c
@@ -82,6 +82,11 @@ static inline int perf_intr_is_nmi(struct pt_regs *regs)
return 0;
}
+static inline int siar_valid(struct pt_regs *regs)
+{
+ return 1;
+}
+
#endif /* CONFIG_PPC32 */
/*
@@ -106,14 +111,20 @@ static inline unsigned long perf_ip_adjust(struct pt_regs
*regs)
* If we're not doing instruction sampling, give them the SDAR
* (sampled data address). If we are doing instruction sampling, then
* only give them the SDAR if it corresponds to the instruction
- * pointed to by SIAR; this is indicated by the [POWER6_]MMCRA_SDSYNC
- * bit in MMCRA.
+ * pointed to by SIAR; this is indicated by the [POWER6_]MMCRA_SDSYNC or
+ * the [POWER7P_]MMCRA_SDAR_VALID bit in MMCRA.
*/
static inline void perf_get_data_addr(struct pt_regs *regs, u64 *addrp)
{
unsigned long mmcra = regs->dsisr;
- unsigned long sdsync = (ppmu->flags & PPMU_ALT_SIPR) ?
- POWER6_MMCRA_SDSYNC : MMCRA_SDSYNC;
+ unsigned long sdsync;
+
+ if (ppmu->flags & PPMU_SIAR_VALID)
+ sdsync = POWER7P_MMCRA_SDAR_VALID;
+ else if (ppmu->flags & PPMU_ALT_SIPR)
+ sdsync = POWER6_MMCRA_SDSYNC;
+ else
+ sdsync = MMCRA_SDSYNC;
if (!(mmcra & MMCRA_SAMPLE_ENABLE) || (mmcra & sdsync))
*addrp = mfspr(SPRN_SDAR);
@@ -230,6 +241,24 @@ static inline int perf_intr_is_nmi(struct pt_regs *regs)
return !regs->softe;
}
+/*
+ * On processors like P7+ that have the SIAR-Valid bit, marked instructions
+ * must be sampled only if the SIAR-valid bit is set.
+ *
+ * For unmarked instructions and for processors that don't have the SIAR-Valid
+ * bit, assume that SIAR is valid.
+ */
+static inline int siar_valid(struct pt_regs *regs)
+{
+ unsigned long mmcra = regs->dsisr;
+ int marked = mmcra & MMCRA_SAMPLE_ENABLE;
+
+ if ((ppmu->flags & PPMU_SIAR_VALID) && marked)
+ return mmcra & POWER7P_MMCRA_SIAR_VALID;
+
+ return 1;
+}
+
#endif /* CONFIG_PPC64 */
static void perf_event_interrupt(struct pt_regs *regs);
@@ -1291,6 +1320,7 @@ struct pmu power_pmu = {
.event_idx = power_pmu_event_idx,
};
+
/*
* A counter has overflowed; update its count and record
* things if requested. Note that interrupts are hard-disabled
@@ -1324,7 +1354,7 @@ static void record_and_restart(struct perf_event *event,
unsigned long val,
left += period;
if (left <= 0)
left = period;
- record = 1;
+ record = siar_valid(regs);
event->hw.last_period = event->hw.sample_period;
}
if (left < 0x80000000LL)
@@ -1374,8 +1404,10 @@ unsigned long perf_instruction_pointer(struct pt_regs
*regs)
{
unsigned long use_siar = regs->result;
- if (use_siar)
+ if (use_siar && siar_valid(regs))
return mfspr(SPRN_SIAR) + perf_ip_adjust(regs);
+ else if (use_siar)
+ return 0; // no valid instruction pointer
else
return regs->nip;
}
diff --git a/arch/powerpc/perf/power7-pmu.c b/arch/powerpc/perf/power7-pmu.c
index 1251e4d..441af08 100644
--- a/arch/powerpc/perf/power7-pmu.c
+++ b/arch/powerpc/perf/power7-pmu.c
@@ -373,6 +373,9 @@ static int __init init_power7_pmu(void)
strcmp(cur_cpu_spec->oprofile_cpu_type, "ppc64/power7"))
return -ENODEV;
+ if (pvr_version_is(PVR_POWER7p))
+ power7_pmu.flags |= PPMU_SIAR_VALID;
+
return register_power_pmu(&power7_pmu);
}
--
1.7.1
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