linux-kernel - [tip:perf/urgent] perf/x86/intel: Fix regression by default disabling perfmon v4 interrupt handling

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Date:   Tue, 20 Nov 2018 09:59:10 -0800
From:   tip-bot for Peter Zijlstra <tipbot@...or.com>
To:     linux-tip-commits@...r.kernel.org
Cc:     alexander.shishkin@...ux.intel.com, vincent.weaver@...ne.edu,
        mingo@...nel.org, torvalds@...ux-foundation.org,
        eranian@...gle.com, linux-kernel@...r.kernel.org,
        robert@...llahan.org, kan.liang@...ux.intel.com, acme@...hat.com,
        peterz@...radead.org, hpa@...or.com, tglx@...utronix.de,
        jolsa@...hat.com, me@...ehuey.com
Subject: [tip:perf/urgent] perf/x86/intel: Fix regression by default
 disabling perfmon v4 interrupt handling

Commit-ID:  2a5bf23d5b795d5df33dc284e8f5cf8b6a5b4042
Gitweb:     https://git.kernel.org/tip/2a5bf23d5b795d5df33dc284e8f5cf8b6a5b4042
Author:     Peter Zijlstra <peterz@...radead.org>
AuthorDate: Tue, 20 Nov 2018 18:08:42 +0100
Committer:  Ingo Molnar <mingo@...nel.org>
CommitDate: Tue, 20 Nov 2018 18:57:48 +0100

perf/x86/intel: Fix regression by default disabling perfmon v4 interrupt handling

Kyle Huey reported that 'rr', a replay debugger, broke due to the following commit:

  af3bdb991a5c ("perf/x86/intel: Add a separate Arch Perfmon v4 PMI handler")

Rework the 'disable_counter_freezing' __setup() parameter such that we
can explicitly enable/disable it and switch to default disabled.

To this purpose, rename the parameter to "perf_v4_pmi=" which is a much
better description and allows requiring a bool argument.

[ mingo: Improved the changelog some more. ]

Reported-by: Kyle Huey <me@...ehuey.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@...radead.org>
Cc: Alexander Shishkin <alexander.shishkin@...ux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@...hat.com>
Cc: Jiri Olsa <jolsa@...hat.com>
Cc: Kan Liang <kan.liang@...ux.intel.com>
Cc: Linus Torvalds <torvalds@...ux-foundation.org>
Cc: Peter Zijlstra <peterz@...radead.org>
Cc: Robert O'Callahan <robert@...llahan.org>
Cc: Stephane Eranian <eranian@...gle.com>
Cc: Thomas Gleixner <tglx@...utronix.de>
Cc: Vince Weaver <vincent.weaver@...ne.edu>
Cc: acme@...nel.org
Link: http://lkml.kernel.org/r/20181120170842.GZ2131@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@...nel.org>
---
 Documentation/admin-guide/kernel-parameters.txt |  3 ++-
 arch/x86/events/intel/core.c                    | 12 ++++++++----
 2 files changed, 10 insertions(+), 5 deletions(-)

diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
index 81d1d5a74728..5463d5a4d85c 100644
--- a/Documentation/admin-guide/kernel-parameters.txt
+++ b/Documentation/admin-guide/kernel-parameters.txt
@@ -856,7 +856,8 @@
 			causing system reset or hang due to sending
 			INIT from AP to BSP.
 
-	disable_counter_freezing [HW]
+	perf_v4_pmi=	[X86,INTEL]
+			Format: <bool>
 			Disable Intel PMU counter freezing feature.
 			The feature only exists starting from
 			Arch Perfmon v4 (Skylake and newer).
diff --git a/arch/x86/events/intel/core.c b/arch/x86/events/intel/core.c
index 273c62e81546..af8bea9d4006 100644
--- a/arch/x86/events/intel/core.c
+++ b/arch/x86/events/intel/core.c
@@ -2306,14 +2306,18 @@ static int handle_pmi_common(struct pt_regs *regs, u64 status)
 	return handled;
 }
 
-static bool disable_counter_freezing;
+static bool disable_counter_freezing = true;
 static int __init intel_perf_counter_freezing_setup(char *s)
 {
-	disable_counter_freezing = true;
-	pr_info("Intel PMU Counter freezing feature disabled\n");
+	bool res;
+
+	if (kstrtobool(s, &res))
+		return -EINVAL;
+
+	disable_counter_freezing = !res;
 	return 1;
 }
-__setup("disable_counter_freezing", intel_perf_counter_freezing_setup);
+__setup("perf_v4_pmi=", intel_perf_counter_freezing_setup);
 
 /*
  * Simplified handler for Arch Perfmon v4: