[4.2.y-ckt stable] Patch "perf/x86: fix PEBS issues on Intel Atom/Core2" has been added to the 4.2.y-ckt tree

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    perf/x86: fix PEBS issues on Intel Atom/Core2

to the linux-4.2.y-queue branch of the 4.2.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-4.2.y-queue

This patch is scheduled to be released in version 4.2.8-ckt3.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 4.2.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

---8<------------------------------------------------------------

>From 029260958a232c329da7b896344dc1fa43b83f50 Mon Sep 17 00:00:00 2001
From: Stephane Eranian <eranian at google.com>
Date: Thu, 3 Dec 2015 23:33:18 +0100
Subject: perf/x86: fix PEBS issues on Intel Atom/Core2

commit 1424a09a9e1839285e948d4ea9fdfca26c9a2086 upstream.

This patch fixes broken PEBS support on Intel Atom and Core2
due to wrong pointer arithmetic in intel_pmu_drain_pebs_core().

The get_next_pebs_record_by_bit() was called on PEBS format fmt0
which does not use the pebs_record_nhm layout.

Signed-off-by: Stephane Eranian <eranian at google.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz at infradead.org>
Cc: Arnaldo Carvalho de Melo <acme at redhat.com>
Cc: Jiri Olsa <jolsa at redhat.com>
Cc: Linus Torvalds <torvalds at linux-foundation.org>
Cc: Peter Zijlstra <peterz at infradead.org>
Cc: Thomas Gleixner <tglx at linutronix.de>
Cc: Vince Weaver <vincent.weaver at maine.edu>
Cc: kan.liang at intel.com
Fixes: 21509084f999 ("perf/x86/intel: Handle multiple records in the PEBS buffer")
Link: http://lkml.kernel.org/r/1449182000-31524-3-git-send-email-eranian@google.com
Signed-off-by: Ingo Molnar <mingo at kernel.org>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 arch/x86/kernel/cpu/perf_event_intel_ds.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kernel/cpu/perf_event_intel_ds.c b/arch/x86/kernel/cpu/perf_event_intel_ds.c
index 71fc402..dbe8d89 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_ds.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_ds.c
@@ -1027,6 +1027,13 @@ get_next_pebs_record_by_bit(void *base, void *top, int bit)
 	void *at;
 	u64 pebs_status;

+	/*
+	 * fmt0 does not have a status bitfield (does not use
+	 * perf_record_nhm format)
+	 */
+	if (x86_pmu.intel_cap.pebs_format < 1)
+		return base;
+
 	if (base == NULL)
 		return NULL;

@@ -1112,7 +1119,7 @@ static void intel_pmu_drain_pebs_core(struct pt_regs *iregs)
 	if (!event->attr.precise_ip)
 		return;

-	n = (top - at) / x86_pmu.pebs_record_size;
+	n = top - at;
 	if (n <= 0)
 		return;

--
1.9.1