diff mbox series

[4/7] perf/x86/amd/ibs: Don't include randomized bits in get_ibs_op_count()

Message ID 20200817220628.7604-4-kim.phillips@amd.com
State Accepted
Commit 680d69635005ba0e58fe3f4c52fc162b8fc743b0
Headers show
Series None | expand

Commit Message

Kim Phillips Aug. 17, 2020, 10:06 p.m. UTC 
get_ibs_op_count() adds hardware's current count (IbsOpCurCnt) bits
to its count regardless of hardware's valid status.

According to the PPR for AMD Family 17h Model 31h B0 55803 Rev 0.54,
if the counter rolls over, valid status is set, and the lower 7 bits
of IbsOpCurCnt are randomized by hardware.

Don't include those bits in the driver's event count.

Signed-off-by: Kim Phillips <kim.phillips@amd.com>
Fixes: 8b1e13638d46 ("perf/x86-ibs: Fix usage of IBS op current count")
Link: https://bugzilla.kernel.org/show_bug.cgi?id=206537
Cc: Stephane Eranian <eranian@google.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Ingo Molnar <mingo@kernel.org>
Cc: Ingo Molnar <mingo@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Borislav Petkov <bp@alien8.de>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@kernel.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Mark Rutland <mark.rutland@arm.com>
Cc: Michael Petlan <mpetlan@redhat.com>
Cc: Namhyung Kim <namhyung@kernel.org>
Cc: LKML <linux-kernel@vger.kernel.org>
Cc: x86 <x86@kernel.org>
Cc: stable@vger.kernel.org
---
 arch/x86/events/amd/ibs.c | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)
diff mbox series

Patch

diff --git a/arch/x86/events/amd/ibs.c b/arch/x86/events/amd/ibs.c
index 8ddce7dd2c4a..ffeb24d31c3d 100644
--- a/arch/x86/events/amd/ibs.c
+++ b/arch/x86/events/amd/ibs.c
@@ -334,11 +334,15 @@  static u64 get_ibs_op_count(u64 config)
 {
 	u64 count = 0;
 
+	/*
+	 * If the internal 27-bit counter rolled over, the count is MaxCnt
+	 * and the lower 7 bits of CurCnt are randomized.
+	 * Otherwise CurCnt has the full 27-bit current counter value.
+	 */
 	if (config & IBS_OP_VAL)
-		count += (config & IBS_OP_MAX_CNT) << 4; /* cnt rolled over */
-
-	if (ibs_caps & IBS_CAPS_RDWROPCNT)
-		count += (config & IBS_OP_CUR_CNT) >> 32;
+		count = (config & IBS_OP_MAX_CNT) << 4;
+	else if (ibs_caps & IBS_CAPS_RDWROPCNT)
+		count = (config & IBS_OP_CUR_CNT) >> 32;
 
 	return count;
 }