From: Ravi Bangoria <ravi.bangoria@amd.com>
Date: Wed, 15 Jan 2025 05:44:32 +0000 (+0000)
Subject: perf/amd/ibs: Fix ->config to sample period calculation for OP PMU
X-Git-Tag: v6.15-rc1~217^2~54
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=598bdf4fefff5af4ce6d26d16f7b2a20808fc4cb;p=thirdparty%2Fkernel%2Flinux.git

perf/amd/ibs: Fix ->config to sample period calculation for OP PMU

Instead of using standard perf_event_attr->freq=0 and ->sample_period
fields, IBS event in 'sample period mode' can also be opened by setting
period value directly in perf_event_attr->config in a MaxCnt bit-field
format.

IBS OP MaxCnt bits are defined as:

  (high bits) IbsOpCtl[26:20] = IbsOpMaxCnt[26:20]
  (low bits)  IbsOpCtl[15:0]  = IbsOpMaxCnt[19:4]

Perf event sample period can be derived from MaxCnt bits as:

  sample_period = (high bits) | ((low_bits) << 4);

However, current code just masks MaxCnt bits and shifts all of them,
including high bits, which is incorrect. Fix it.

Signed-off-by: Ravi Bangoria <ravi.bangoria@amd.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Acked-by: Namhyung Kim <namhyung@kernel.org>
Link: https://lkml.kernel.org/r/20250115054438.1021-4-ravi.bangoria@amd.com
---

diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index bd8919e7c3b17..f95542b75b916 100644
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -271,7 +271,7 @@ static int perf_ibs_init(struct perf_event *event)
 {
 	struct hw_perf_event *hwc = &event->hw;
 	struct perf_ibs *perf_ibs;
-	u64 max_cnt, config;
+	u64 config;
 	int ret;
 
 	perf_ibs = get_ibs_pmu(event->attr.type);
@@ -313,10 +313,19 @@ static int perf_ibs_init(struct perf_event *event)
 		if (!hwc->sample_period)
 			hwc->sample_period = 0x10;
 	} else {
-		max_cnt = config & perf_ibs->cnt_mask;
+		u64 period = 0;
+
+		if (perf_ibs == &perf_ibs_op) {
+			period = (config & IBS_OP_MAX_CNT) << 4;
+			if (ibs_caps & IBS_CAPS_OPCNTEXT)
+				period |= config & IBS_OP_MAX_CNT_EXT_MASK;
+		} else {
+			period = (config & IBS_FETCH_MAX_CNT) << 4;
+		}
+
 		config &= ~perf_ibs->cnt_mask;
-		event->attr.sample_period = max_cnt << 4;
-		hwc->sample_period = event->attr.sample_period;
+		event->attr.sample_period = period;
+		hwc->sample_period = period;
 	}
 
 	if (!hwc->sample_period)