linux-kernel - [PATCH 7/9] x86, perf: Handle new arch perfmon v4 status bits

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Message-Id: <1431285767-27027-8-git-send-email-andi@firstfloor.org>
Date:	Sun, 10 May 2015 12:22:45 -0700
From:	Andi Kleen <andi@...stfloor.org>
To:	peterz@...radead.org
Cc:	eranian@...gle.com, linux-kernel@...r.kernel.org,
	Andi Kleen <ak@...ux.intel.com>
Subject: [PATCH 7/9] x86, perf: Handle new arch perfmon v4 status bits

From: Andi Kleen <ak@...ux.intel.com>

ArchPerfmon v4 has some new status bits in GLOBAL_STATUS.
These need to be ignored when deciding whether a NMI
was a NMI to avoid eating all NMIs when they
stay set (see b292d7a104)

This patch ignores the new ASIF bit, which indicates
that SGX interfered with the PMU, and also the new
LBR freezing bits, which are set when the LBRs get
frozen, plus the existing CondChange (set by JTAG debuggers
and some buggy BIOSes)

Signed-off-by: Andi Kleen <ak@...ux.intel.com>
---
 arch/x86/kernel/cpu/perf_event_intel.c | 13 +++++++------
 1 file changed, 7 insertions(+), 6 deletions(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel.c b/arch/x86/kernel/cpu/perf_event_intel.c
index 39fcd07..2c8a268 100644
--- a/arch/x86/kernel/cpu/perf_event_intel.c
+++ b/arch/x86/kernel/cpu/perf_event_intel.c
@@ -1821,13 +1821,14 @@ again:
 	intel_pmu_lbr_read();
 
 	/*
-	 * CondChgd bit 63 doesn't mean any overflow status. Ignore
-	 * and clear the bit.
+	 * Ignore a range of extra bits in status that do not indicate
+	 * overflow by themselves.
 	 */
-	if (__test_and_clear_bit(63, (unsigned long *)&status)) {
-		if (!status)
-			goto done;
-	}
+	status &= ~(GLOBAL_STATUS_COND_CHG |
+		    GLOBAL_STATUS_ASIF |
+		    GLOBAL_STATUS_LBRS_FROZEN);
+	if (!status)
+		goto done;
 
 	/*
 	 * PEBS overflow sets bit 62 in the global status register
-- 
1.9.3

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