linux-kernel - [kvm-unit-tests patch v2 7/7] x86: pmu_pebs: Support to validate timed PEBS record on GNR/SRF

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Message-Id: <20250718013915.227452-8-dapeng1.mi@linux.intel.com>
Date: Fri, 18 Jul 2025 09:39:15 +0800
From: Dapeng Mi <dapeng1.mi@...ux.intel.com>
To: Sean Christopherson <seanjc@...gle.com>,
	Paolo Bonzini <pbonzini@...hat.com>
Cc: kvm@...r.kernel.org,
	linux-kernel@...r.kernel.org,
	Jim Mattson <jmattson@...gle.com>,
	Mingwei Zhang <mizhang@...gle.com>,
	Zide Chen <zide.chen@...el.com>,
	Das Sandipan <Sandipan.Das@....com>,
	Shukla Manali <Manali.Shukla@....com>,
	Yi Lai <yi1.lai@...el.com>,
	Xiaoyao Li <xiaoyao.li@...el.com>,
	Dapeng Mi <dapeng1.mi@...el.com>,
	Dapeng Mi <dapeng1.mi@...ux.intel.com>,
	Kan Liang <kan.liang@...ux.intel.com>
Subject: [kvm-unit-tests patch v2 7/7] x86: pmu_pebs: Support to validate timed PEBS record on GNR/SRF

On Intel GNR/SRF platform, timed PEBS is introduced. Timed PEBS adds
a new "retired latency" field in basic info group to show the timing
info. IA32_PERF_CAPABILITIES.PEBS_TIMING_INFO[bit 17] is introduced to
indicate whether timed PEBS is supported.

After introducing timed PEBS, the PEBS record format field shrinks to
bits[31:0] and  the bits[47:32] is used to record retired latency.

Thus shrink the record format to bits[31:0] accordingly and avoid the
retired latency field is recognized a part of record format to compare
and cause failure on GNR/SRF.

Please find detailed information about timed PEBS in section 8.4.1
"Timed Processor Event Based Sampling" of "Intel Architecture
Instruction Set Extensions and Future Features".

Reviewed-by: Kan Liang <kan.liang@...ux.intel.com>
Signed-off-by: Dapeng Mi <dapeng1.mi@...ux.intel.com>
Tested-by: Yi Lai <yi1.lai@...el.com>
---
 lib/x86/pmu.h  | 6 ++++++
 x86/pmu_pebs.c | 8 +++++---
 2 files changed, 11 insertions(+), 3 deletions(-)

diff --git a/lib/x86/pmu.h b/lib/x86/pmu.h
index c7dc68c1..86a7a05f 100644
--- a/lib/x86/pmu.h
+++ b/lib/x86/pmu.h
@@ -20,6 +20,7 @@
 #define PMU_CAP_LBR_FMT	  0x3f
 #define PMU_CAP_FW_WRITES	(1ULL << 13)
 #define PMU_CAP_PEBS_BASELINE	(1ULL << 14)
+#define PMU_CAP_PEBS_TIMING_INFO	(1ULL << 17)
 #define PERF_CAP_PEBS_FORMAT           0xf00
 
 #define EVNSEL_EVENT_SHIFT	0
@@ -188,4 +189,9 @@ static inline bool pmu_has_pebs_baseline(void)
 	return pmu.perf_cap & PMU_CAP_PEBS_BASELINE;
 }
 
+static inline bool pmu_has_pebs_timing_info(void)
+{
+	return pmu.perf_cap & PMU_CAP_PEBS_TIMING_INFO;
+}
+
 #endif /* _X86_PMU_H_ */
diff --git a/x86/pmu_pebs.c b/x86/pmu_pebs.c
index 2848cc1e..bc37e8e3 100644
--- a/x86/pmu_pebs.c
+++ b/x86/pmu_pebs.c
@@ -277,6 +277,7 @@ static void check_pebs_records(u64 bitmask, u64 pebs_data_cfg, bool use_adaptive
 	unsigned int count = 0;
 	bool expected, pebs_idx_match, pebs_size_match, data_cfg_match;
 	void *cur_record;
+	u64 format_mask;
 
 	expected = (ds->pebs_index == ds->pebs_buffer_base) && !pebs_rec->format_size;
 	if (!(rdmsr(MSR_CORE_PERF_GLOBAL_STATUS) & GLOBAL_STATUS_BUFFER_OVF)) {
@@ -289,6 +290,8 @@ static void check_pebs_records(u64 bitmask, u64 pebs_data_cfg, bool use_adaptive
 		return;
 	}
 
+	/* Record format shrinks to bits[31:0] after timed PEBS is introduced. */
+	format_mask = pmu_has_pebs_timing_info() ? GENMASK_ULL(31, 0) : GENMASK_ULL(47, 0);
 	expected = ds->pebs_index >= ds->pebs_interrupt_threshold;
 	cur_record = (void *)pebs_buffer;
 	do {
@@ -296,8 +299,7 @@ static void check_pebs_records(u64 bitmask, u64 pebs_data_cfg, bool use_adaptive
 		pebs_record_size = pebs_rec->format_size >> RECORD_SIZE_OFFSET;
 		pebs_idx_match = pebs_rec->applicable_counters & bitmask;
 		pebs_size_match = pebs_record_size == get_pebs_record_size(pebs_data_cfg, use_adaptive);
-		data_cfg_match = (pebs_rec->format_size & GENMASK_ULL(47, 0)) ==
-				 (use_adaptive ? pebs_data_cfg : 0);
+		data_cfg_match = (pebs_rec->format_size & format_mask) == (use_adaptive ? pebs_data_cfg : 0);
 		expected = pebs_idx_match && pebs_size_match && data_cfg_match;
 		report(expected,
 		       "PEBS record (written seq %d) is verified (including size, counters and cfg).", count);
@@ -327,7 +329,7 @@ static void check_pebs_records(u64 bitmask, u64 pebs_data_cfg, bool use_adaptive
 			       pebs_record_size, get_pebs_record_size(pebs_data_cfg, use_adaptive));
 		if (!data_cfg_match)
 			printf("FAIL: The pebs_data_cfg (0x%lx) doesn't match with the effective MSR_PEBS_DATA_CFG (0x%lx).\n",
-			       pebs_rec->format_size & 0xffffffffffff, use_adaptive ? pebs_data_cfg : 0);
+			       pebs_rec->format_size & format_mask, use_adaptive ? pebs_data_cfg : 0);
 	}
 }
 
-- 
2.34.1