[PATCH 5.16 244/285] perf/x86/intel: Dont extend the pseudo-encoding to GP counters

Greg Kroah-Hartman
2022-04-12T08:11:07Z

From: Kan Liang <kan.liang@linux.intel.com>

commit 4a263bf331c512849062805ef1b4ac40301a9829 upstream.

The INST_RETIRED.PREC_DIST event (0x0100) doesn't count on SPR.
perf stat -e cpu/event=0xc0,umask=0x0/,cpu/event=0x0,umask=0x1/ -C0

Performance counter stats for 'CPU(s) 0':

607,246 cpu/event=0xc0,umask=0x0/
0 cpu/event=0x0,umask=0x1/

The encoding for INST_RETIRED.PREC_DIST is pseudo-encoding, which
doesn't work on the generic counters. However, current perf extends its
mask to the generic counters.

The pseudo event-code for a fixed counter must be 0x00. Check and avoid
extending the mask for the fixed counter event which using the
pseudo-encoding, e.g., ref-cycles and PREC_DIST event.

With the patch,
perf stat -e cpu/event=0xc0,umask=0x0/,cpu/event=0x0,umask=0x1/ -C0

Performance counter stats for 'CPU(s) 0':

583,184 cpu/event=0xc0,umask=0x0/
583,048 cpu/event=0x0,umask=0x1/

Fixes: 2de71ee153ef ("perf/x86/intel: Fix ICL/SPR INST_RETIRED.PREC_DIST encodings")
Signed-off-by: Kan Liang <kan.liang@linux.intel.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: stable@vger.kernel.org
Link: https://lkml.kernel.org/r/1648482543-14923-1-git-send-email-kan.liang@linux.intel.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
arch/x86/events/intel/core.c | 6 +++++-
arch/x86/include/asm/perf_event.h | 5 +++++
2 files changed, 10 insertions(+), 1 deletion(-)

--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -5521,7 +5521,11 @@ static void intel_pmu_check_event_constr
/* Disabled fixed counters which are not in CPUID */
c->idxmsk64 &= intel_ctrl;

- if (c->idxmsk64 != INTEL_PMC_MSK_FIXED_REF_CYCLES)
+ /*
+ * Don't extend the pseudo-encoding to the
+ * generic counters
+ */
+ if (!use_fixed_pseudo_encoding(c->code))
c->idxmsk64 |= (1ULL << num_counters) - 1;
}
c->idxmsk64 &=
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -241,6 +241,11 @@ struct x86_pmu_capability {
#define INTEL_PMC_IDX_FIXED_SLOTS (INTEL_PMC_IDX_FIXED + 3)
#define INTEL_PMC_MSK_FIXED_SLOTS (1ULL << INTEL_PMC_IDX_FIXED_SLOTS)

+static inline bool use_fixed_pseudo_encoding(u64 code)
+{
+ return !(code & 0xff);
+}
+
/*
* We model BTS tracing as another fixed-mode PMC.
*