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

tip-bot for Peter Zijlstra
2018-11-20T18:01:03Z

Commit-ID: 2a5bf23d5b795d5df33dc284e8f5cf8b6a5b4042
Gitweb: https://git.kernel.org/tip/2a5bf23d5b795d5df33dc284e8f5cf8b6a5b4042
Author: Peter Zijlstra <peterz@infradead.org>
AuthorDate: Tue, 20 Nov 2018 18:08:42 +0100
Committer: Ingo Molnar <mingo@kernel.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@kylehuey.com>
Signed-off-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Cc: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
Cc: Jiri Olsa <jolsa@redhat.com>
Cc: Kan Liang <kan.liang@linux.intel.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Robert O'Callahan <robert@ocallahan.org>
Cc: Stephane Eranian <eranian@google.com>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Vince Weaver <vincent.weaver@maine.edu>
Cc: acme@kernel.org
Link: http://lkml.kernel.org/r/20181120170842.GZ2131@hirez.programming.kicks-ass.net
Signed-off-by: Ingo Molnar <mingo@kernel.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: