linux-kernel - [PATCH] perf/x86/intel: Don't extend the pseudo-encoding to GP counters

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Message-Id: <1648482543-14923-1-git-send-email-kan.liang@linux.intel.com>
Date:   Mon, 28 Mar 2022 08:49:02 -0700
From:   kan.liang@...ux.intel.com
To:     peterz@...radead.org, mingo@...hat.com,
        linux-kernel@...r.kernel.org
Cc:     eranian@...gle.com, Kan Liang <kan.liang@...ux.intel.com>,
        stable@...r.kernel.org
Subject: [PATCH] perf/x86/intel: Don't extend the pseudo-encoding to GP counters

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

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@...ux.intel.com>
Cc: stable@...r.kernel.org
---
 arch/x86/events/intel/core.c      | 6 +++++-
 arch/x86/include/asm/perf_event.h | 5 +++++
 2 files changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index db32ef6..1d2e49d 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -5668,7 +5668,11 @@ static void intel_pmu_check_event_constraints(struct event_constraint *event_con
 			/* 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 &=
diff --git a/arch/x86/include/asm/perf_event.h b/arch/x86/include/asm/perf_event.h
index 48e6ef56..cd85f03 100644
--- a/arch/x86/include/asm/perf_event.h
+++ b/arch/x86/include/asm/perf_event.h
@@ -242,6 +242,11 @@ 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.
  *
-- 
2.7.4