linux-kernel - [PATCH 1/2] perf/x86/intel/pt: Add interface to stop Intel PT logging

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Date:	Wed, 28 Oct 2015 17:25:47 +0900
From:	Takao Indoh <indou.takao@...fujitsu.com>
To:	Thomas Gleixner <tglx@...utronix.de>,
	Ingo Molnar <mingo@...hat.com>,
	"H. Peter Anvin" <hpa@...or.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Arnaldo Carvalho de Melo <acme@...nel.org>,
	Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
	Vivek Goyal <vgoyal@...hat.com>
CC:	<linux-kernel@...r.kernel.org>, <x86@...nel.org>
Subject: [PATCH 1/2] perf/x86/intel/pt: Add interface to stop Intel PT logging

This patch add a function for external component to stop Intel PT.
Basically this function is used when kernel panic occurs. When it is
called, intel_pt driver disables Intel PT and saves its registers using
pt_event_stop, which is also used by pmu.stop handler. This function
stops Intel PT on the cpu where it is working, therefore user need to
call it for each cpu to stop all logging.

Signed-off-by: Takao Indoh <indou.takao@...fujitsu.com>
---
 arch/x86/include/asm/intel_pt.h           |   10 ++++++++++
 arch/x86/kernel/cpu/perf_event_intel_pt.c |    9 +++++++++
 2 files changed, 19 insertions(+), 0 deletions(-)
 create mode 100644 arch/x86/include/asm/intel_pt.h

diff --git a/arch/x86/include/asm/intel_pt.h b/arch/x86/include/asm/intel_pt.h
new file mode 100644
index 0000000..3bfe971
--- /dev/null
+++ b/arch/x86/include/asm/intel_pt.h
@@ -0,0 +1,10 @@
+#ifndef _ASM_X86_INTEL_PT_H
+#define _ASM_X86_INTEL_PT_H
+
+#if defined(CONFIG_PERF_EVENTS) && defined(CONFIG_CPU_SUP_INTEL)
+void cpu_emergency_stop_pt(void);
+#else
+void cpu_emergency_stop_pt(void) {}
+#endif
+
+#endif /* _ASM_X86_INTEL_PT_H */
diff --git a/arch/x86/kernel/cpu/perf_event_intel_pt.c b/arch/x86/kernel/cpu/perf_event_intel_pt.c
index 4216928..a638b5b 100644
--- a/arch/x86/kernel/cpu/perf_event_intel_pt.c
+++ b/arch/x86/kernel/cpu/perf_event_intel_pt.c
@@ -27,6 +27,7 @@
 #include <asm/perf_event.h>
 #include <asm/insn.h>
 #include <asm/io.h>
+#include <asm/intel_pt.h>
 
 #include "perf_event.h"
 #include "intel_pt.h"
@@ -1125,6 +1126,14 @@ static int pt_event_init(struct perf_event *event)
 	return 0;
 }
 
+void cpu_emergency_stop_pt(void)
+{
+	struct pt *pt = this_cpu_ptr(&pt_ctx);
+
+	if (pt->handle.event)
+		pt_event_stop(pt->handle.event, PERF_EF_UPDATE);
+}
+
 static __init int pt_init(void)
 {
 	int ret, cpu, prior_warn = 0;
-- 
1.7.1


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