: powerpc/perf: Sample only if SIAR-Valid bit is set in P7+

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.

---
 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(-)

index 078019b..9710be3 100644
@@ -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()

index a1096fb..d24c141 100644
@@ -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

index 1251e4d..441af08 100644
@@ -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